ANNEX 1:
1.
1.1.
TECHNICAL SPECIFICATIONS: DOUBLE REGULATING TURBINE GOVERNOR
Type and Description
The turbine governor shall be provided, complete with actuator, guide vane, governor cubicle,
restoring mechanism & transmitters, motor-driven oil pumping units, pressure tank, sump tank,
operation oil, oil piping, guide vanes servomotors, speed sensing equipment, hydraulic overspeed
device, regulating ring hydraulic operated lock, hydraulic operated cooling water valve and all
parts and accessories required to make a complete unit for regulating the speed and controlling
the guide vanes of the turbine in accordance with the requirements specified below.
The governor shall be of the proportional – integral –derivative [PID] Numerical Electro-Hydraulic
type and shall be guaranteed by the Contractor to fulfill the requirements of this Specification.
The governor shall be protected from the effects of electrostatic discharge, radiated
electromagnetic fields and conducted or induced fast transients or bursts of noise.
The governor shall be designed so that electromagnetic interference does not cause mal-operation
of the control system or damage of the components. The Contractor shall explain his design basis
for electromagnetic tolerance.
The necessary apparatus and auxiliary devices shall be provided to facilitate interface to the Unit
control system via hard wired interface.
1.2.
Operating Requirements
The governor shall be equipped with all necessary automatic auxiliary devices to permit full
automatic operation of the starting, build up of speed, synchronizing and pick-up of load to pre
determined manual setting, load/frequency regulation and stopping of the turbine – generator
unit.
The governor shall be capable of controlling the speed of the turbine stably when operated at no
load, or when operated at the rated speed with isolated load at any power output. The governor
shall also be capable of controlling the output of turbine at any power output when operated in
parallel with other generators in the plant or in the transmission network.
During normal operation, regulation of unit power and network frequency are according to actual
frequency reference [i.e. frequency influence], power reference and permanent speed droop value.
1.3. Governor Components
The governor shall be complete with the following items. The Contractor is to ensure that all
necessary items are supplied, whether or not they are specified herein.
1.3.1. Control Unit
This shall comprise an electro-hydraulic transducer which converts an electrical regulating signal
into a hydraulic valve movement and causes the turbine guide vanes to move in a direction and to
an extent demanded by the regulator.
1.3.2. Guide Vane Distributing Valve
This valve shall control the flow of pressure oil to and from the guide vane servomotors.
1.3.3. Guide Vane Auxiliary Distributing Valve
This valve shall be supplied and arranged for direct manual control of the turbine guide vanes. An
auxiliary selector valve shall be provided to change from main distributing valve control to
auxiliary distributing valve control. An indicator on or near the actuator shall be provided to show
which type of control is selected.
Push buttons for raise/lower control of the turbine guide vanes shall be installed in the turbine
Governor control panel for use when operating the guide in manual position.
1.3.4. Guide Vane Limit Mechanism
This function will limit the maximum and minimum guide vane position both during the start
sequence and normal operation. Limitation to prevent operation of reverse power and operating
on zones where cavitation can occur shall be provided.
The Unit Automatic Control equipment will initially open the limiter to a predetermined value
upon closing of the Generator breaker (preferably 80%). Afterwards the limiter device can be
controlled freely from the control room to any setting by the operators.
1.3.5. Guide Vane Locks
The servomotors shall be equipped with locking devices that shall be capable of maintaining the
servomotors on either the fully open or fully closed positions. The closing lock shall be
automatically applied when the unit is shut down such that the guide vanes shall remain fully
closed against maximum reservoir level even if the oil pressure is reduced. The closing lock shall
be released as part of the start-up sequence. The open position lock is to be applied manually to
ensure operation safety while working within the turbine with the guide-vanes in open position.
Both locks shall be capable of resisting the maximum force that can be applied at the oil pressure
was inadvertently applied and shall be interlocked with the unit start-stop system. Alternative
locking arrangements which achieve the same performance will be considered.
Limit switches shall be installed for status indication on the position of the locks. These shall be
connected to the control system for start/stop interlocking.
All necessary supply and return oil pipes etc. shall be provided and installed in accordance with
the standard technical requirements.
1.3.6. Emergency Shutdown mechanism
The Hydraulic control assembly shall be able to close the guide vane servomotor in the event of
malfunctions such as:
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Failure of the Governor Power supply.
Failure of an element in the control loop
Minimum pressure in the pressure oil system
In order to fulfill the above safety requirements, an emergency trip command signal shall be
included in the hydraulic loop. This loop shall comprise of emergency trip acting valves to
include:
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The minimum pressure emergency trip valve.
The solenoid valve for electrical trip signals.
By spring action during the emergency situation these valves shall change over from the operating
position to the emergency trip position and hence closes the guide vane servomotors.
The valves shall be provided with auxiliary contacts, which indicate when the device are energized
and de-energized respectively. The equipment shall be rated for continuous duty on 110 V D.C.
.
1.3.7. Restoring Mechanism
The actual position of the servomotors and the distributor valves for the Guide vanes will be given
by position transmitters. Two redundant position transmitters for the servomotors and distributor
valves shall be required such that a failure in one will not affect the operation of the positioning
controller and an alarm will be indicated.
The position transmitters shall be mounted appropriately and their connecting cables shall be
connected to the governor electronic cubicle with properly screened cables, which shall be routed
to minimize the possibility of interference or damage.
The mechanism shall be complete with all supports, clamps, brackets, protection against
mechanical damage and any other item required to complete the installation.
1.3.8. Hydraulic Mechanical Overspeed
The turbine shaft shall be equipped with a suitable mechanical overspeed detector which shall
apply full oil pressure to the closing side of guide vane servomotors. The operating speed shall be
adjustable but will be initially calibrated to operate when the turbine speed is 140%. The
mechanical overspeed device shall be fully interlocked with the unit tripping and shall in parallel
with its direct action an emergency shutdown. The device shall be reset manually. Appropriate
guard will be provided for the sensor device assembly.
Electrical contacts rated at 250 V 6A shall be interfaced to the Unit electrical tripping scheme.
1.3.9. Speed Signal Generator
Unit speed shall be measured with either the following methods: Use of system VT and generator VT measurement to synthesize the respective frequencies.

Use of inductive switches: Two inductive detectors that shall be driven by a toothed wheel
to be mounted on the turbine shaft. The Contractor shall submit a proposal on how to
mount the toothed wheel to the turbine shaft in situ. The Contractor shall provide suitable
cover or guard for the speed detection device. The signal shall be transferred into the
processor speed device, which will transform it to the required form. Failure of one of the
inductive detectors will not affect the operation of the governor equipment and an alarm
will be issued. If both inductive detectors fail, automatic changeover to manual governor
mode procedure shall be activated.
1.3.10. Alarm, Trip, Indication and Control Devices
Protection functions shall be included but not limited to the following:
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Failure of both inductive detectors for unit speed measurement or VT measurement.
Failure of servomotor position transmitter measuring device.
Actuator device not responding.

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Digital governor failure.
Failure of both power supplies.
The above protection function shall initiate emergency shutdown procedure of the unit.
All faults messages shall be indicated both and hard wired to the unit control board.
Quantities shall be indicated at the Governor cubicle but not limited to the following:
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Guide vane position
Turbine speed
Guide vane limiter position
Actual power output
Penstock and Tailrace pressure
Governor oil pressure
Net Head
All governing system alarms and trips functions shall be indicated by approved means at the
Governor Cubicle. These are all abnormal conditions that may arise in the system. These systems
includes but not limited to the followings:
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Governor processor
Pressure receiver accumulator
Sump Tank
Speed measuring system
Oil Level
Loss of oil pressure
Governor Pumps
These shall also be hard wired to the unit control board.
The control features that shall be provided shall include but not limited to the following:
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Selection switches, key operated
 Operation/Parameter selection
 Manual/Automatic selector
 Local/Remote operation
Control Modes selection pushbuttons
 Speed Control – Network
 Speed Control –Isolated
 Load Control with selectable frequency influence via selector switch.
 Opening Control
Push buttons for start, stop
power Set point adjustments(raise/lower)
Load/power analog set-point
Limiter set point(raise/lower)
Governor manual control adjustments
Checking and changing of governor parameters.
The governor commands shall be possible from both the governor panel and the Unit Automation
depending on the selection of the governor control (local /remote). These shall also be hard wired
to the unit control board.
1.3.11. Electrical Control Devices
The governor shall be complete with the following items. The Numerical electronic control unit
shall be housed in one floor standing panel/cubicle.
1.3.11.1.
Numerical Electronic Control Unit.
A modern numerical based electronic unit of the PID type shall be supplied to control the position
of the guide vanes.
Speed adjustment device with a range of 90 to 110% of the rated Speed adjustable while the turbine
is operating. This device shall be controlled at this panel and also electrically from the control
room.
Power adjustment device with a range of 0 to 100% full load adjustable under the turbine loaded.
This shall be controlled at this panel and also electrically from the control Room.
Gate limiting device shall be provided to be controlled manually at the panel and also electrically
from the control room.
The control unit shall introduce the necessary stabilising and correction signals and transmit the
governing signal to the electro-hydraulic control unit of the guide vanes..
Protection against high voltage surges and transients shall be provided in all systems using solid
state components. The surge protection shall be adequate to protect against system or component
failure from either externally or internally produced surges.
1.3.11.2.
Main Processing Unit and Memory
The main processing unit and memory shall be suitable sized for the application. The Contractor
shall provide details of the equipment proposed. This information shall include the unit
configuration, memory structure, type and capacity, execution times, the effects of adding
peripherals and a description of the diagnostic functions.
The Governor Equipment shall be capable of I/O forcing and simulation, for test, commissioning
and maintenance purposes. These functions shall be facilitated through a locally connected
programmer. The I/O forcing shall be only be possible by use of security passwords or key
switching.
The Governor Equipment shall be programmed by high level programming language that is userfriendly. Windows pull down menus and mouse control interface software shall be provided.
1.3.11.3.
Supervision of Governor Controller
Comprehensive self testing and self diagnostic facilities are required to be included in the Governor
equipment.
The monitoring of the governor controller shall include but not limited to the following functions.
The Contractor shall provide details of the following facilities offered:


Correct application program scanning check,
Memory integrity checks.
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Validity of data exchange between memories, processing units and I/O modules.
Power supply check
Main processor unit status check,
I/O channel integrity check.
Error message display
Integral supervision functions
Powerful aid for testing
Other self test and diagnostic execution details.
Self monitoring of the processor
Process connections
Actuator and transducers
Speed sensor failure.
The Contractor shall also provide details of the facility proposed for reporting the self test and
diagnostic message. Output contacts shall be provided for external fault indication and interfaced
to the unit control board.
1.3.11.4.
Synchronizing Speed Control/Frequency matching.
During the synchronizing, the network frequency with a small deviation (beat frequency) will be
used as frequency reference. The difference between generator and network phase angle will then
periodically be zero, making it possible to synchronize the unit. However, a selector control shall
also be provided to allow the governor’s internal frequency reference to be used and at this time
the frequency reference shall be adjustable using raise/lower push buttons or the synchronizing
relay mounted on the unit control board.
A selector switch shall be provided to select between frequency matching by governor itself or by
the auto synchronizer. The selector may be implemented in the Automation (unit Control Panels).
The governor shall ignore the commands from the auto synchronizer when selected to do the
function of frequency matching.
1.3.11.5.
Power and Frequency measurement
The Generator’s current metering transformer and the Network’s voltage transformer shall be used
as a source for measuring power. Network frequency shall be measured from the network voltage
transformer.
The accuracy of the frequency measurement shall be higher than 0.01%.
The accuracy of power measurement shall be higher than 1%.
Current transformer terminals blocks shall be furnished with short circuiting facilities to short the
main CT such that secondary injection tests can be performed without open circuiting the CTs. The
design of terminal blocks shall be such that measurement of secondary currents shall be possible
while the unit is running.
1.3.12. Governor Power Supplies
The Governor Control voltage shall be 24Vdc supply. Dual redundant power supplies shall be
provided and shall draw power from both DC and AC sources as follows below:-


DC supply -110 Volts Nominal [Range +15 % /-20%]
AC supply - 240 Volts 50Hz Nominal [Range +5 % /-10%]
Failure of one source of supply shall not affect the operation of the governor equipment. An output
contact indicating failure of any of the power source shall be provided. The primary and secondary
voltages of the power supply shall be galvanically isolated.
For lighting and heating of the cubicle 240Vac 50 Hz supply will be used. Cubicle lighting shall
be controlled by a door switch.
1.3.13. Manual Control Mode facility
Manual control facility shall also be provided in form of electronic cards for control of guide-vane
servomotor. The cards shall have mode selection (manual/Auto) and necessary controls and
indications. In auto mode, the control of guide-vane servomotor shall be by the governor signal.
1.3.14. Net Head Signal Equipment
Dam level and Tailrace level equipment shall be provided for real time dam level monitoring. The
outputs from these devices shall be used by the governor to determine the net head.
The mounting position of the dam level transducers shall be agreed upon during the preliminary
design stage.
1.3.15. Speed Monitoring System
Speed monitoring system shall be provided.
The system shall serve to detect measure, evaluate and monitor machine Rev/Min signal up to
200% nominal speed. The system shall be driven by two inductive pick-up sensors driven by the
toothed wheel (mentioned under governor speed sensing device) or frequency measured from the
system and generator VTs. Failure of one pick-up sensor shall not affect the operation of the system
but an alarm condition will be indicated by an output contact. Detection of failure on one or both
of the pick-ups shall be incorporated and wired via relays on to the output terminals.
Two additional separate electrical overspeed devices complete with inductive speed pick-up shall
also be provided.
1.3.16. Speed Level Detection
The system shall have at least 6(six) monitoring speed level that can be set to operate within a
range of 3- 200% of the nominal speed. Output interposing cut-off relays contacts shall be SPDT
with rating of 250Vac, 6A or better, shall be provided.
1.3.17. Analog Output Signal
The system shall have mA output signal (4 – 20mA) to the unit control board for the following
functions: Speed Indicator with red mark at unit rated speed
 Guide vane position.
 Limiter position
 Governor oil pressure
1.4. Governor Cubicle construction
The Governor cubicle shall be of rittal standard, floor-mounted and free standing construction for
indoor installation with cable entry from the bottom. Ventilation points shall be provided with
suitable removable air filters to prevent the ingress of dust and insects. Cooling air fans shall be
incorporated in the Governor equipment
Cubicle size and colour shall match the Unit Control cubicles.
The Governor cubicle shall be of tropical design and to IP54 Protection code of practice according
to IEC529.
The cubicle shall be fitted with lifting eye bolts which shall be removed after installation.
All metal parts other than those forming part of an electrical circuit shall be connected in an
approved manner to separate earth bars running along the bottom of the panel. The metal cases of
all instruments and the like shall be connected to the copper earth bars by conductors of not less
than 2.5sq mm or by other approved means.
Doors shall be fitted with handles and locks [key operated]. The cubicle shall contain internal
power sockets. Door operated cubicle internal lighting shall be provided.
All instrument and control devices shall be easily accessible and capable of being removed from
the panel for maintenance purposes. Labels permanently attached to the panel shall identify each
relay and electronic card within the panel and adjacent to the equipment concerned.
All control relays shall be robust and firmly supported on their bases by use of retainer clips or
springs to avoid looseness that may occur due to vibration.
The cubicle shall be made of sheet steel not less than 2.0mm thick.
Devices and component shall be mounted and labeled according to number and function.
The Governor Equipment cubicle shall have terminal blocks for reception of cables cores (2.5 mm2)
for interfacing to the other plant control equipment. All wiring shall be of adequate cross section
area to carry prospective short circuit without risk of damage to conductors, insulation or joints.
Wiring shall be supported using an insulated system, which allows easy access for faults finding
and facilitate the installation of additional wiring. Ribbon cables cables with plug and sockets
connectors may be used for light current wiring. Plug and socket connector shall be polarized so
that they can be inserted into one another in the correct manner. All wiring shall be identified in
accordance with the associated schematic and/or wiring diagrams by means of discrete wire
numbers.
All internal electrical wiring for the governor cabinet shall be neatly terminated. All wiring shall
be insulated with 600-volt grade oil-proof material. All connections shall be made at terminal
blocks. Terminal blocks shall be provided and rated not less than 600-volt, and shall be provided
with covers. At least 10 per cent extra terminals shall be provided in each group or terminal
blocks.
Permanent identification of all terminals wires shall be provided.
A consistent system of wire numbering approved by the client shall be used throughout the
equipment.
1.4.1. Peripherals and Software Package
All peripherals to the Governor Equipment, such as programming units shall be supplied as part
of this contract. Client staff shall be trained on how to these equipment for plant maintenance and
future plant modifications. The programming unit shall operate at 240V, 50Hz. The software
package with the necessary license shall be provided.
The Contractor shall provide details of the facilities to be included. This shall cover the method of
programming program storage, program loading and program documentation.
Any modifications to an existing program shall be protected by password or key-switch security.
The portable programming units shall be capable of providing the facilities for local Governor fault
finding, self diagnostic facilities and commissioning. Details of the programming, de bugging,
maintenance, fault finding and diagnostic facilities shall be provided by Contractor.
The necessary software build to operate under windows environment shall be supplied. The
software will display the signal values/level in the Governor on the screen of the portable device
in an analogue manner.
The software will provide functions to modify, store, compare the running program with file, test
and for graphical documentation of the program.
A hardcopy of the software program including all the parameters setting and range shall be
provided in the documentation.
The operating software shall also be provided in a CD form for future loading into another PC.
Cable to connect the PC to the governor equipment shall be supplied.
1.5. Training:
A comprehensive training on the governor, operating software and control PLC algorithms shall
be conducted by the contractor to client Engineers to equip them with sufficient knowledge on
how to maintain and carry out future modifications on the Governor system. This shall be done
before the commencement of the factory acceptance tests.
A five (5) Tier training program is recommended as follows to help in attaining full technology
transfer to client Engineers:
a) Basic Training prior to project programs development to absorb the software general
concepts
b) Participation in project programs development during design(attachment to Contractor)
c) FAT participation testing
d) Participation in commissioning of the project program (attachment to Contractor)
e) Site training in the configured project programs
The contractor shall present a training proposal that shall be discussed and agreed upon with the
client during the preliminary design.
1.6.
Facilities to enable Remote Regulation.
The governor shall be designed to accept the following control commands/functions from the unit
control board.
 start/ stop commands
 Raise and lower commands for power /load control
 Raise and lower commands for limiter position
 load/power analog set-point
 Selection command between load regulation by Raise/Lower commands and Analog setpoint shall be provided.
 Selection of all governor control modes.
 Speed Isolated
 Speed Isolated Network Operation
 Load Control – with inbuilt frequency threshold band outside which the governor
will automatically change-over from load control to speed control Isolated
 Load Control with selectable frequency Influence.
 Shutdown commands (Emergency tripping).
Load control shall be in two ways:a. Using the Digital Raise/Lower commands.
b. Using the analogue set point.
If the Raise/Lower commands are operated when the analogue set point is ON, these shall take
priority.
The necessary feedback signals shall be provided to the automation via hard wired interface.
1.7. Facilities to enable Local control Regulation.
The following command shall be established to enable control of the governor from the local panel.
 start/ stop commands push buttons
 Raise and lower commands for power /load control
 Raise and lower commands for limiter position
 Selection of all governor control modes.
 Speed Isolated
 Speed Isolated Network Operation
 Load Control – with inbuilt frequency threshold band outside which the governor
will automatically change-over from load control to speed control Isolated
 Load Control with selectable frequency Influence.
1.8. Cables and Cabling Works
Cables shall be provided for interconnections between the Governor equipments/devices to the
Unit Automation system and Power supply boards. The cable shall be shielded and steel armoured.
These cables shall carry all the signals including the power supplies. The ends of the cable to the
governor components shall be provided with appropriate plug and socket connectors that shall be
polarized so that they can be inserted into one another in the correct manner for easy removal
during maintenance. Cables shall be well labeled at both ends.
Necessary cable support systems shall be provided.
1.9. Governor Oil Pressure Supply Equipment
The oil pressure system shall be designed for use to control the Guide vanes, the MIV and by pass
systems and the cooling water valve.
This equipment shall be designed to supply sufficient pressure oil to the guide vane servomotors
via the governor and distributing valves to open and close the guide vanes through their full travel.
It shall include but not limited to the following: An oil sump,
 One pressure tank/accumulator,
 main and standby governor oil pumps,
 piping,
 valves
 Cooling system
 all other ancillary items to form a complete installation
The equipment shall be designed to minimize the requirement for site commissioning and shall as
far as possible consist of a single assembly which can be factory tested prior to shipment.
The main control valve shall be directly controlled by the start/stop valve and shall form part of
the oil supply assembly. The control valves and associated equipment shall preferably be assembled
from standard CETOP components and mounted on a common valve block.
The contractor shall provide the operating oil for the governor system.
1.9.1. Sump Tank
The sump tank shall have a capacity of at least 110% of all the oil in the sump and pressure tank(s)
under normal operating conditions. It shall be designed to carry the two motor driven oil pumps
and shall be provided with a manhole for access to the interior; an oil level gauge; operating oil;
oil fill and drain connections; and oil purifier connections. A breather shall be fitted on the sump
tank and shall incorporate a moisture filter.
Two PT100 temperature detectors shall be also incorporated to monitor the oil temperature. Sight
oil gauge shall be furnished.
All control and monitoring equipment [i.e. low, pump stop level, normal & high oil level,
continuous level indication [4-20mA], etc.] for efficient operation shall also be provided.
1.9.2. Oil Pumps and Auxiliaries.
Oil pumping set with duty and standby pump motors shall be provided. Each pump shall be selfpriming at any time after the units are commissioned.
The pumping set shall be complete with sump tank, duty/standby electrically driven pumps,
valves, monitoring devices, duplex filters (with pressure differential alarm), high and low tank
level switches and all other parts necessary to integrate the system into the unit control system.
When the turbine is running the duty pump shall run continuously to maintain the system
pressure. Pump operation shall also be supervised by a pressure switch for alarm.
The standby pump shall operate under pressure switch control. The pumps shall be rated such that
the standby pump will not start when the guide-vanes are moved through a full opening stroke
followed by a full closing stroke with initial oil pressure at minimum of the range of duty pump
operation. Pump operation shall also be supervised by a pressure switch.
It shall be possible to select any pump to duty or standby. ‘Standby pump running’ alarm shall be
provided.
The pumps local control operation shall be provided in a separate panel. The panel shall house the
local controls for the governor oil pumps. State indications, current consumption ammeters and
associated CTs, running hour counters, start/stop push buttons, fault indication, pump selection
switch, emergency stop buttons and key operated selector switches for local and remote operation
shall be provided. All necessary signals shall be interfaced to the unit control board.
The oil pumps shall draw power from the new 415 board that shall be supplied under this contract.
The specification of this board is indicated elsewhere in this document. The board electrical
components [i.e. pump contactors, switches, indicators, overload protection, fuses and it’s carrier
etc] shall be designed in order that the circuit functions/copes to requirements of the new oil pump
motors.
The pump motors will be arranged for direct on line starting with the pump unloaded.
The control system shall be arranged such that the pumping unit remains operative following a
failure of the unit on start/stop system such that the system can be operated under manual control.
1.9.3. Governor Oil Cooling System
Separate oil cooling system shall be provided with heat exchanger, oil circulation pump, piping
for both oil and water, valves, cooling water flow meters (contacts and continuous flow), PT 100
for inlet and outlet cooling water temperature monitoring and any other necessary materials. The
heat exchanger shall be of a suitable material for the application to the approval of the client.
Cooling water shall be drawn from the Penstock through a hydro cyclone for each river.
Strainer device shall be provided in the oil circulation circuit and an alarm shall be provided if the
differential pressure across the strainer exceeds a threshold.
Provision shall be made for oil refilling to the sump by external means.
The oil circulation pump shall have two operation modes:Auto -by sump oil temperature
Manual – by ON/OFF push buttons
The oil circulation pump shall draw power from the new 415 board that shall be supplied under
this contract
1.9.4. Pressure Tank/Accumulator(s)
One tank of welded construction shall be provided having a volume capable of operating the guide
vanes three full strokes and the MIV two (2) full strokes at the rated minimum pressure and oil
level. The tank shall be fitted with the following items and any other items required for the safe
and efficient operation of the oil system: 
Pressure Relief Valve
One automatic pressure relief valve of adequate capacity mounted at the top of each tank.

Sight Oil level Gauges
One oil level gauge to indicate the oil level in each tank. Each gauge shall be fitted with a
metal guard, stop valves and automatic shut-off devices to prevent the escape of oil in the
event of glass breakage.
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Oil level Alarms
High and Low oil level alarm devices each electrically-independent and arranged to close
to give alarm. The high level alarm device shall be set at a level to indicate failure to
maintain the oil volume. The low level alarm device shall be set to operate when there is
only sufficient oil left in the tank to provide two total servomotor volumes. Further oil level
switches may be necessary for automatic pumps stop when the level of oil in the sump tank
is below the operating level.
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Pressure indication and control Switches
The following shall be provided:
 Pressure gauge for local indication of pressure.
 Transmitting unit for connection to local pressure indicator and remote pressure
indicator at the generator control panel.
 Pressure switches
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Ancillary Items
The tank(s) shall be provided with the necessary connection for the pressure lines with
shut-off valve; man-doors; drain connections; lifting lugs; and foundation bolts, nuts,
washers, etc. to complete installation.
1.9.5. Guide Vane Servomotors
Two oil pressure servomotors shall be furnished to connect to the guide vane operating ring by
means of two push/pull rods having adequate length adjustment facilities. The servomotors shall
be provided with an oil pipe work system connecting them to the governor oil distributing valve.
At minimum oil pressure, the double-acting servomotors shall be capable of moving the turbine
guide vanes through a full opening stroke or a full closing stroke at the rated closing time with
maximum gross head plus maximum water hammer pressure acting on the turbine. At this
pressure, the servomotor shall be capable of holding the turbine guide vanes closed to prevent the
runner rotating.
The assembly shall be designed to withstand the maximum reaction in either direction. The
arrangement shall be such that the total guide vane operating force shall be divided approximately
equally between the two servomotors which shall direct their efforts to opposite sides of, and
tangentially to, the guide vane operating ring. The system shall be designed such that failure of any
pipework will not allow fast closing of the guide vanes.
The cylinders, pistons and piston rings shall be of approved materials chosen to restore mutual
compatibility. The surface of the piston rods shall be hard chrome plated incorporating suitable
renewable seals to prevent oil leakage along the piston rod. The cylinders shall be provided with
flanged main oil pipe connections, a pressure gauge tapping at each end complete with isolating
needle valve, air release valves, and drain connections with pipework fittings and valves.
Each servomotor shall be provided with a device to retard the rate of closing from just below the
speed/no-load position to the fully closed position. This device shall not affect the rate of opening
from the closed position.
Each of the following devices shall be fitted on one or other of the two servomotors, or on the guide
vane operating ring: A scale and pointer to indicate percentage of servomotor stroke from the fully closed
position.
 A connection for the governor restoring mechanism.
 A mechanical locking device of simple construction capable of locking the guide vanes
in the open position and of withstanding safely the maximum operating force of both
servomotors.
 An automatic hydraulic locking device for maintaining the guide vanes in the closed
position. This shall be incorporated in the start-stop sequence of the Unit.
1.9.6. Oil Pressure Piping
All interconnecting piping and valves between the oil pumps, sump tank, pressure tank, actuator,
distributing valves, and turbine servomotors shall be included in the supply. All pipework and
associated fittings on the oil system shall be flanged and if loose flanges are provided for welding
on site, springing of pipes into position to make connections will not be permitted. The governor
units shall be located in the powerhouse generally but the final layout shall be for agreement
between the Contractor and the client.
Valves shall be provided such that main items of equipment can be isolated for maintenance.
The pipework system shall be well supported and arranged in sections to allow easy dismantling
during turbine maintenance. The pipe work shall be arranged so that oil cannot drain from
servomotor cylinders, control valves or pipe work when the pressure oil supply is off. Air release
points shall be provided on the servomotors and as necessary in the pipe work.
1.9.7. Nitrogen Bottles
Nitrogen Bottles for maintaining the governor pressure in the pressure tank (Piston accumulator)
shall be supplied. These shall be well connected to the piston accumulator with appropriate pipe
work. A pressure gauge shall be mounted on the nitrogen bottles for use during maintenance.
1.9.8. Penstock and Tailrace pressure Indication
Ultra-precise pressure transducers and indications for Penstock and Tailrace level shall be
furnished and installed in the governor cubicle. Necessary interconnecting cables, pipe work and
materials shall also be furnished.
1.9.9. Inspection and Testing

Factory tests
All equipment shall be subject to tests in accordance with relevant applicable standards. All
the governor parts (Hydraulic and electrical) shall be tested connected together as a system.
This shall include but not limited to: - digital governor, sump tank, pressure tank, nitrogen
bottles etc. necessary piping shall be provided for interconnecting the parts to a working
system.
The governor acceptance tests shall be performed according to IEC 60308 (Testing of speed
governing systems for hydraulic turbines) with the exception that the test items difficult to
perform on Site, may be done in the factory.
The client shall witness the factory tests.

Site tests during erection and preliminary functional test.
During the installation of each of the equipment tests shall be performed, to establish the
accuracy of the assembly and to prove the adequacy of the materials and the workmanship.
All tests and test procedures with test recording sheets shall be submitted to the Client at
least three (3) weeks to the execution of the Tests. The client shall review and incorporate
amendments to the procedures and tests.
The Contractor shall perform the following tests, for all items where applicable, to ensure
that the equipment has been correctly installed all necessary adjustments and settings made
and that the item is in sound condition to run under load.
A. Inspection during installation of equipment



Pressure test of pressure oil tank and piping for pressure oil system
Calibration of dial type thermometers
Calibration of pressure gauges
B. Preliminary functional test










Measurement of oil pump discharge pressure
Continuous operation test of oil pump (heat run)
Automatic start and stop test of stand-by oil pump
Measurement of oil pressure build-up time
Capacity test of oil pressure tank
Adjustment and setting of safety valve
Check of oil level control system
Leakage test of oil(tank and all pipe lines)
Setting of oil level and pressure switches
Insulation resistance measurement of motor
C. Operational tests and adjustments








Adjustment and setting of servomotor feedback transducers
Operation of servo valve with numerical governor
Operation of governor manual control
Overall governor operation test at no load
Normal Start and Stop operational tests
Quick shutdown test and Emergency Trip
Setting and checking of adopted times for turbine gate stroke
Preliminary setting of speed monitoring system and operational checks







Adjustment and setting of guide vane closing and opening times
Overspeed tests.
Load rejection tests at 25%, 50%, 75% and 100%.
Relation between guide vane servomotor opening and generator output (output test)
Quick load increase test
Permanent speed droop measurement
Heat run test
D. Performance tests
After the Governor equipment has been installed, tested, and/or its mechanical and dryout
runs has been successfully completed and approved and the generating unit has been fully
operational, the Contractor shall carry out the performance tests in the presence of the
Client to demonstrate that all guarantees and technical particulars as listed in the Tender
and Contract Documents have been satisfied and that the entire Equipment is properly
installed, free from objectionable defects and correctly adjusted to operate as specified.
The performance tests shall include but not limited to the following items:
E. Reliability run
After the performance tests and before Taking Over, Contractor shall carry out the
reliability run to demonstrate satisfactory operation of Governor equipment and associated
devices.
The reliability run shall be carried out under the Contractor’s responsibility.
The period of the reliability run shall be 30days.
When the Equipment is inoperable due to external fault or any cause beyond the
Contractor’s responsibility, an extension of time will be given equivalent to the lost time.
Should the external problem persist for more than one week, then the Contractor and Client
will discuss and agree on the best way forward.
The reliability run shall include the start-stop test of the generating equipment which shall
be carried out by the Contractor twice a day during a period of the reliability run.
1.9.10. Spare Parts.
The Contractor shall provide spare parts that he recommends should be held by the client to enable
the equipment to be operated efficiently for a period of 10 years. The spares shall include but not
limited to the following:






One numerical Governor Unit
One Power supply pack of each type provided in the governor
Three output Relays of each type
Three input relays/opto-coupler of each type
Two speed pick-up sensors
Two position transducers of each type
Two servo valve of each type









Oil filters of each type
Solenoid valves, one of each type
One hydraulic valve of each type
One oil pump of each type complete with motor
One oil circulation pump complete with motor
Sets of oil seals kit
One pressure gauge of each type
One operator panel
One Speed Monitoring device of each type
1.10. MIV and By-pass control system:
The MIV and by pass systems shall be operated by the same pressure system operating the guide
vanes. Control Valves for control of MIV, by pass and cooling water system shall be established and
mounted on the oil sump tank as those of the governor control.
The control valves and associated equipment for MIV and by-pass valve shall preferably be
assembled from standard CETOP components and mounted on a common valve block on the sump
tank. The control voltage to the coils shall be powered via 110Vdc power supply.
The closing of the MIV shall be via a counter weight correctly rated to close the MIV at the highest
penstock pressure.
A key operated selector switch for MIV and by pass control shall be provided. Contacts of this
selector switch shall be used to interlock the open/close control commands. The selector switch
shall have the following levels of control.
 Local/Maintenance control: Control of MIV and by pass valve at the local control panel.
Open/close push buttons for both MIV and By-pass intergraded with status indication LEDs
(24Vdc) shall be provided.

Remote Control: Control of MIV and by pass valve at the unit control board.
Status indication: Robust limit switches shall be provided and mounted on the MIV and by-pass for
the following indications: MIV open and closed position.
 By-pass open and closed position.
These limit switches shall be wired to energize robust multiplying relays whose contacts shall be
interfaced for both local and remote indication.
1.11. Cooling water valve.
A cooling water valve and associated isolating valves for each unit shall be supplied. This shall tap
water from the main cooling water line.
The cooling water valve shall be operated (close/open) by the governor oil pressure via a bistable
control valve.
The bistable control valve shall have solenoid coils operating at 110Vdc and shall be mounted on
the same valve block where the MIV and by pass control valves are mounted.
Limit switches for valve status indication shall be mounted on the cooling water valve and
interfaced to the unit control board.
ANNEX 2:
2.
TECHNICAL SPECIFICATIONS: PLANT INSTRUMENTATION
2.1. Introduction
The new Wanjii units shall be equipped with modern instrumentation for control and monitoring.
All necessary instruments for control and monitoring of the plants shall be furnished and
commissioned in each plant system.
Instrumentation shall be provided but not limited to the following systems: Governor and MIV systems
 Excitation system.
 Plant Bearings.
 Cooling water system
 Dam and tail race level measurement
 Generator temperature monitoring
 Dewatering and drainage system.
 Portal valve
2.2. Governor and MIV systems
The governor and MIV systems shall be supplied complete with sufficient control and monitoring
instruments to make them full functioning systems. A minimum of the instruments defined in
Annex 1 shall be furnished. The contractor may include any other Governor instruments he deems
necessary for the safe operation of the plant.
2.3. Excitation system
The excitation systems shall be supplied complete with sufficient control and monitoring
instruments to make them full functioning systems. A minimum of the instruments defined in
Annex 4 shall be furnished. The contractor may include any other excitation instruments he deems
necessary for the safe operation of the plant.
2.4. Unit Bearings:
Instruments shall be furnished for control and monitoring of the following bearing parameters: Bearing oil sump levels (Contacts for oil level low alarm and oil level too low trip and 420mA signal for real time monitoring). Dial gauge thermometers with contacts for alarm
and trip shall be installed as a back-up temperature monitoring system. The contacts shall
be wired to annunciate at both the unit control board (SCADA) and alarm panel mounted
on the auxiliaries’ board.
 All Bearing pads temperature measurement by use of PT100. Dial gauge thermometers with
contacts for alarm and trip shall be installed as a back-up temperature monitoring system.
The contacts shall be wired to annunciate at both the unit control board (SCADA) and alarm
panel mounted on the auxiliaries’ board.
 Oil temperature measurement by use of PT100.
These shall be interfaced to the unit control PLC for temperature alarming and tripping.
Alarm and trip set point screen/menu shall be provided in the SCADA for adjusting the alarm and
trip levels of the RTDs.
2.5.
Cooling water system:
The cooling water shall be supplied via two hydro-cyclones. One Hydro cyclone shall be connected
to the Maragua River penstock while the other shall tap water from the Mathioya River.
The outlet of the two hydro cyclones shall be interconnected via a common header where each
unit shall draw its cooling water.
Each unit shall have its cooling water drawn from the common header through hydraulically
operated valves and isolating valves.
The hydraulic valve shall be operated by use of the governor pressure. Correctly rated valves shall
be used for open/close commands and mounted on the same valve block as the MIV control valves.
Valve status indication robust limit switches shall be mounted on the cooling water valve and the
contacts connected the common PLC and Auxiliaries board for control and indication.
Other parameters shall be monitored by use of the following instruments: Water pressure before each hydro-cyclone.
 Cooling water pressure for each unit. To be connected after the hydraulic operated valve.
 Cooling water temperature (Both inlet and outlet).
2.6.

Dam and tail race level measurement
Dam level and Tailrace level equipment shall be provided real time level monitoring.
Preferably radar level measurement instruments shall be used. The contract shall install
appropriate equipment to transmit the signals to the SCADA system for real time level
monitoring. The level in the SCADA shall be calibrated in METERS ABOVE SEA LEVEL
(mASL).
. The appropriate mounting positions shall be agreed with the client during the preliminary design
stage of the project.
2.7. Generator temperature monitoring
Appropriate four wire RTDs shall be installed in the generator stator winding, stator slots and stator
core for real time generator temperature monitoring. These shall be interfaced to the unit control
PLC for stator temperature alarming and tripping.
Algorithms in the PLC program shall be made such that failure of one RTD does not trip the unit.
However, the unit shall trip if temperatures rise in two or more RTDs beyond the trip set point.
Alarm and trip set point screen/menu shall be provided in the SCADA for adjusting the alarm and
trip levels of the RTDs.
2.8. Drainage and Dewatering system
The drainage and dewatering system shall be rehabilitated by the client. The pumps shall draw
power from the new 415Vac distribution board.
A minimum of the following control facilities and instruments shall be provided under this
contract: Local control board; this shall have a key operated selector switch for local/automatic
selection. When the pumps are selected local; Control shall be via push buttons installed at
this panel. When the control is selected to automatic, the pumps shall be controlled
automatically by the level switches.
 A selector switch shall also be provided for duty/standby changeover of the pumps.
 A minimum of the following level switches shall be provided for control of these pumps:


 Level, stop pumps.
 Level high, start duty pump.
 Level high, start standby pump.
 Level high, alarm
 Level too high, station shutdown.
Contacts of the level switches and selector switches shall also be interfaced to the SCADA
system for monitoring the drainage pump scheme.
A radar level transducer shall be installed for real time level monitoring of the drainage
scheme in the SCADA system. The level in the SCADA shall be calibrated in METERS ABOVE
SEA LEVEL (mASL).
2.9. Control of portal valve
A new hydraulically controlled portal valve shall be supplied and installed in this contract. The
contractor shall provide a complete hydraulic system with a control board for operations of the
portal valve and the associated by pass valve.
The hydraulic and control board shall include pushbuttons for open/close of both the portal valve
and bypass valve, status indication instruments, pressure indication instruments for both the
pressure system and penstock, pumping units, control valves, oil sump tank, pressure relief valve
etc. The closing of the valve shall be via a counterweight system.
Pressure transducers shall be installed in both the downstream and upstream sides of the portal
valve to interlock opening of the portal valve if the pressures are not balanced.
Interlocking shall be made such that when a command is given to open the portal valve, the bypass
valve opens first to balance the pressure on both sides of the penstock. The bypass shall then close
when the portal valve is open.
All necessary instruments shall be provided for the safe operation of the hydraulic system of the
portal valve.
ANNEX 3:
1.1.1. UNIT CONTROL AND SCADA SYSTEM
1.2. General description:
The units shall have two modes of control namely; Manual control and automatic control.
The manual control facility for the units shall be achieved by running/controlling the systems from
their respective local panels. A systems auxiliaries control panel complete with push buttons for
start/stop, LED alarm fascia, synchronizing system etc shall be established and mounted next to
the Governor and excitation panel to facilitate full manual control of each unit.
The automatic control shall be achieved by running/controlling the respective unit systems via the
unit control board PLC.
The new Wanjii automatic Control system shall be PLC based. Each unit shall be controlled and
monitored via a dedicated unit PLC. All common auxiliary systems/equipment shall be controlled
and monitored via a separate PLC (Common PLC). Each PLC and associated devices (I/O cards,
power supplies, control relays etc) shall be housed in a dedicated panel of rittal standard referred
to here as Unit control board (UCB).
The unit Control boards shall be hardwired to interface to the field equipment (sensors,
transducers, limit switches, turbine governor, excitation etc).
The unit control board (PLC) shall have three levels of control, namely:A. Local control: This shall be control of the unit via a touch screen industrial PC mounted on
the unit control board (panel). Each dedicated touch screen industrial PC shall
communicate directly to its associated unit PLC.
B. Local control centre: This shall be control of all the units at the common local control centre
described elsewhere in this document. A client-server control system shall be established
with redundant communication network to make a complete control system. Appropriate
HMI control software approved by the client shall be used.
C. Remote control centre: Connect to Kamburu remote control centre (KRCC) and KenGen
Central dispatch Centre (KCDC) as described in 1.3.3.
1.3. Unit Control Board:
Each unit shall have a dedicated unit control board. The unit PLC and associated devices (I/O cards,
power supplies, control relays etc) shall be housed in this panel.
The unit control board shall be interfaced to dedicated unit systems (excitation, Governor, GCB,
etc) through hard wired control logics. The PLC shall be the central control system of each unit
control board.
1.3.1. Unit PLC
A complete proprietary PLC system shall be supplied for each unit. This shall include CPU,
communication cards, power supply cards, input/output cards, network cards etc.
A signal list of all the interface signals (I/O) to the unit PLCs shall be developed and approved by
the client. Each signal shall have a unique signal tag number description that shall be used to
identify the particular signals in the drawings.
All the control logics of the unit shall be via the PLC. Appropriate PLC algorithm logics shall be
programmed in the PLC by use of high level PLC programming language to make safe control logics
for each unit. The PLC control logics shall include the following.


Step by step control of the unit from standstill to grid.
Automatic start/stop of the unit to the following steady state conditions/modes: Standstill to rolling mode
 Standstill to excited mode
 Standstill to grid mode
 Grid to excited mode
 Grid to rolling mode
 Grid to standstill mode
The PLC shall be interfaced to the HMI control system via a dual, redundant communication
network. (See description of control system).
1.3.2. Power Supplies:
Each unit control board shall be equipped with dedicated power supplies for control and
monitoring circuits.
The Control voltage of each unit shall be 24Vdc. Dual redundant power supplies shall be provided
and shall draw power from both DC and AC sources as follows:

DC supply -110 Volts
AC supply - 240 Volts
Failure of one source of supply shall not affect the operation of the unit. An output contact
indicating failure of any of the power source shall be provided. The primary and secondary
voltages of the power supply shall be galvanically isolated.
For lighting and heating of the cubicle 240Vac 50 Hz supply will be used. Cubicle lighting shall
be controlled by a door switch.
1.3.3. Control levels:
It shall be possible to operate each unit in the following control levels:A. Local automatic control: This shall be control of the unit via a tough screen industrial PC
mounted on the unit control board (panel). Each dedicated tough screen industrial PC shall
communicate directly to its associated unit PLC.
B. Local control centre: This shall be control of all the units at the common local control centre.
A client-server control system shall be established with dual, redundant communication
network to make a complete control system. Appropriate HMI control software approved
by the client shall be used.
C. Remote control centre: Connect to Kamburu remote control centre (KRCC) and KenGen
Central dispatch Centre (KCDC).
Remote Operation:
a) Background
KenGen is in the process of establishing a country wide SCADA system that enables monitoring
and control of each of KenGen’s power stations from a central control room. The project will
comprise a central dispatch centre and a number of regional control centres, interfaces to some
twenty power plants (Upgraded Wanjii Power Station being one of the power plant) and a
communications network linking power plants to control centres.
It is anticipated that the new upgraded Wanjii power plant shall be interfaced to Kamburu control
centre (KRCC) and KenGen central dispatch centre (KCDC).
International standard interfaces and communication protocols will be employed to link the power
plant DCS’s to the SCADA control centres via WAN communication links.
Scope of Supply
The scope of supply for the Wanjii power plant interface shall be 2 (Two) gateways to support 2
local communications node each expected to comprise provision of:A DCS gateway or RTU interfaced to the DCS LAN, supporting IEC 60870-5 -104
communications protocols (see attached generic interface diagram).
Additional functionality within the power plant DCS to support remote control of each
generating unit from an AGC module in the SCADA master station at the KenGen Central
Dispatch Centre (KCDC). This shall include facilities and functionality for:

Selecting each unit to operate under AGC and Control level selections

Processing set points or raise / lower signals for modifying unit operating points for
MW and MVAr,

Inputting permitted operating ranges for MW and MVAr and the maximum ramp rates
supported by each generating unit.

Forwarding plant analogue measurements, status, events and alarm information to the
SCADA system via the gateway.

Accepting control commands sent from the KenGen Central Dispatch Centre (KCDC).
The contractor shall configure the Unit Control PLC program to be able to accept control
commands from these remote control stations.
Meter readings from fiscal energy meters associated with each generator via IEC 62056-21
protocol (Electricity metering - Data exchange for meter reading, tariff and load control Part 21: Direct local data exchange) and forwarding the data to the KenGen CDC.
Communication Node 1 is to KenGen CDC (Stima Plaza KenGen)
Communication Node 2 is to KenGen Regional Centre (Kamburu)
Communications
Media
Communications Node
48 V dc Power Supply
(if required)
--/~
--/~
Local Plant User
Interface
RTU
Fieldbus / IEC 104
Conversion
Meter Reading IEC
62056 / IEC 104
Protocol Conversion
Fieldbus
DCS PLCs
Energy
Meter
Generic interface diagram
Notes.
Distances from Wanjii to Stima Plaza (KCDC) is 70 km while that from Wanjii to Kamburu (KRCC)
is approximately 100KM. Distance from KRCC to KCDC is approximately 120 km. The connection
of Wanjii to KRCC is not in the Wanjii upgrading project scope.
D. Manual control: when the control level selector switch is in this position, control of the
units shall be achieved via the local control panels and auxiliaries control panel. However,
it shall be possible to view the plant parameters from the control system HMI screens.
A Key operated selector switch shall be installed in each UCB to change the level of control from
local control (Industrial PC) to local control centre (Operator station) and vice versa. This selector
switch shall also be used to turn the PLC out of service should the need arise to run the units
manually from the local panels.
A software button shall be established in the control screen to transfer control of the unit from the
Wanjii control centre to Tana control centre and vice versa.
1.3.4. SCADA system and Human machine interface (HMI):
A SCADA system control architecture shall be established for the control of the units through a
dual, redundant communication network.
This shall consist of the following:-






Hot standby server system.
Client Operator system PCs (OPS).
Communication network with appropriate switches.
Event log printer.
One coloured printer.
GPS time synchronizing clock connected to the PLCs, server work stations Industrial PCs
and the operator and stations.
The SCADA system shall have client-server communication architecture. The system servers shall
communicate to each PLC through modbus Ethernet communication protocol to receive and send
data while the touch screen industrial PCs shall communicate directly to the dedicated unit PLCs.
The server work stations at Wanjii shall communicate to both the operator stations at Wanjii
control and the server work stations at Tana control centre.
The Wanjii control centre shall have two operator stations. It shall be possible to control the units
from any of the operator stations.
Appropriate control and monitoring graphical screens shall be developed to the approval of the
client. Basically the control functions shall be limited to the main screen while the other
screens/windows shall contain monitoring data and set points for the various plant parameters.
An alarm management screen shall also be implemented.
The control centres at Wanjii control room and Tana shall be complete with appropriate control
room furniture, UPS power supply, UPS outlet sockets, net work switches and telephone systems
etc.
The control room furniture shall have necessary internal cable ducts for network, power and
telephone connections and appropriate facility for storing the operator stations.
The server stations, network switches and associated equipment shall be housed in one cabinet.
The SCADA servers shall be supplied together with additional memory for data archiving and
storage.
KenGen is planning to establish dispatch centres for its power generating plants across the country.
One such dispatch centre is Tana remote control centre. It is expected that all plants in upper Tana
(Wanjii is one of them) shall be remotely controlled from here. Similarly a central data repository
for all the plants shall also be maintained. In this case therefore Plant historical data shall be
maintained in Plant information server located here. This however is not in the Scope of Wanjii
rehabilitation project.
Considering that the Process LAN in Wanjii is client server based, an OPC server application shall
be installed in the redundant server nodes (collectors) and configured for failover. The interfacing,
testing and commissioning to the Plant information system servers at Tana shall be accomplished
in this project. If by the time this project is being commissioned, the Tana plant information servers
will not be ready for interfacing the employer shall provide an alternative Plant Information server
already running and maintained in one of the existing KenGen plants.
The successful bidder shall be required to customize daily report templates to be accessed through
the RTweparts in PI. These reports shall be of agreed analogue parameters where archived values
will be populated in the templates on half hour basis. Monthly reports for parameters such as
energy shall also be customized. The data/parameters to be transmitted shall be agreed upon
during implementation.
An appropriate and reliable communication system to Tana control centre shall be established and
commissioned to link the remote control centre and the local control centre. Control of the units
shall only be possible at the Tana control centre when the control level is selected to remote.
An output from the SCADA system shall be generated to energize the siren module mounted in the
auxiliaries’ panel whenever an alarm occurs in the SCADA system.
A typical communication shall be as shown in the Sketch to be provided below.
Interface to corporate WAN
This shall be done via the corporate Local Area Network (LAN at Wanjii. Appropriate network
security devices shall be provided and configured to ensure only authorized devices in the
corporate network shall access the process LAN at Wanjii power station. Details of devices that
shall be granted access to the process LAN shall be provided during configuration of the network
security devices.
1.4. Auxiliaries control board:
An auxiliaries’ control panel shall be established and mounted next to the Governor and Excitation
control panel.
This panel shall be used for the following functions:A.
B.
C.
D.
Start/stop of all unit auxiliaries.
Synchronizing the unit.
An LED based alarm fascia with alarm reset and acknowledgement buttons.
Indicating instruments for generator active power, reactive power, current and voltage.
1.4.1. Auxiliaries start/stop functions.
All the unit auxiliaries shall be controlled from this panel when the unit control board panel
control level is selected to manual control.
Push buttons with integrated status indication LEDs shall be mounted on this panel and interlocked
with manual level of control.
These auxiliaries include but not limited to the following:


Cooling water valve(Open/Close)
Unit braking system (Apply/Release).
Governor pumps (Start/stop).


Guide vane locks (Apply/release).
Emergency push button.
1.4.2. Unit Synchronizing system:
The Plant synchronizing system shall be installed in this panel.
The synchronizing system shall consist of the following:
A numerical based technology synchronizing relay with push buttons for ON/OFF
Commands and indication.
 Synchro-check relay with inbuilt Synchroscope (with phase angle indicating LEDs).
 Double voltage meter.
 Double frequency meter.
 Raise/Lower center zero control switch for governor control during synchronizing and
loading.
 Raise/Lower center zero control switch for excitation control during synchronizing and
loading.
 Selector switch for manual/automatic synchronization selection.
 Discrepancy switch opening/closing the Generator circuit breaker (GCB).
When the unit is operating at manual control level of command, the synchronizing system shall
be controlled via the ON/OFF push buttons on the auxiliaries’ panel.
When the unit is operating from the unit control board (PLC), the synchronizing system shall be
switched ON by the PLC when the control sequence reaches the synchronizing stage. The PLC shall
switch OFF the synchronizing relay after the GCB is closed.
In the event that the synchronizing relay is faulty, the synchronizing shall be done manually using
the double frequency meter, double voltage meter and the Synchro-check relay. The GCB shall be
closed via the discrepancy control switch.
The numerical based synchronizing relay shall include all the functions required for exact and
reliable synchronizing including synchronizing detection, for generator breaker closing
command. The voltage matching function will control the generator voltage regulator while the
frequency and phase matching function will control the turbine governor.
The device shall be mounted on the front of the auxiliaries’ panel.
The device electronics shall be galvanically isolated from the inputs and outputs. The device shall
also have an operating panel for local operation, maintenance and diagnostics. The operating
panel shall consist of a display (preferably LCD), a keyboard which is access-protected and LED
indicators for a few alarms and indications. Parameters and actual values shall be displayed on a
PC via RS232 serial interface. The software tool shall be provided in a CD and shall also include
the cable to a laptop PC.
The device shall have a feature for external instrument transformer amplitude compensation or
alternatively an internal phase shift compensation feature. A test mode feature is required. Auto
shut off function feature after synchronizing and issue of breaker closing command is required.
The device shall have comprehensive self-monitoring functions consisting of at least:  Periodical checks of A/D transducers
 Monitoring of set point
 Supply voltage
 Memory
 Parameters etc
To ensure maximum safety of the generator and network, while synchronizing, a synchro-check
relay shall be provided as an interlock in series. The scheme shall have a feature ‘dead bus’
paralleling to be used while running the unit on black start sequence.
A suitable PC based software tool for commissioning of the devices shall be provided.
1.4.3. LED based alarm fascia:
An LED based alarm/trips fascia shall be installed on the side of this panel for annunciating any
plant anomaly. This shall consist of grouped alarms from all the dedicated unit systems.
Alarms from the same system/function may be grouped together where applicable. The
alarm/warning LEDs shall be yellow in colour and flashing. The LEDs for trip indication shall be
red in colour and also flashing.
All the alarms and trips shall be annunciated via an approved siren module mounted on top of the
auxiliaries’ panel. The siren module shall consist of the following: Siren: To energize when an alarm/trip occurs.
 Red light: for indication when an alarm/trip occurs.
 Green Light: To indicate when the unit is running.
 Amber light: To indicate when the unit is on standstill.
An output from the SCADA system shall be generated to energize the siren whenever an alarm
occurs in the SCADA system.
A minimum of 50 LEDs shall be used for grouped alarms and trips indication. Where one system
has several alarms, these shall be grouped together in several LEDs.
1.4.4. Indicating instruments:
Indicating instruments shall be mounted on the auxiliaries’ panel with correct units of measure
for the following functions:
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Generator active power.
Generator reactive power.
Generator currents single phase indication.
Generator voltage (three phase indication with line to line selector switch).
 Cooling water pressure.
These instruments shall have a red mark inscribed at nominal values on each meter.
1.4.5. Control Panel Construction:
The control cubicles shall be of rittal standard, floor-mounted and free standing construction for
indoor installation with cable entry from the bottom. Ventilation points shall be provided with
suitable removable air filters to prevent the ingress of dust and insects. Cooling air fans shall be
incorporated in the panels.
Cubicle size and colour shall match the Unit Control cubicles.
The control cubicles shall be of tropical design and to IP54 Protection code of practice according
to IEC529.
The cubicle shall be fitted with lifting eye bolts which shall be removed after installation.
All metal parts other than those forming part of an electrical circuit shall be connected in an
approved manner to separate earth bars running along the bottom of the panel. The metal cases of
all instruments and the like shall be connected to the copper earth bars by conductors of not less
than 2.5sq mm or by other approved means.
Doors shall be fitted with handles and locks [key operated]. The cubicle shall contain internal
power sockets. Door operated cubicle internal lighting shall be provided.
All instrument and control devices shall be easily accessible and capable of being removed from
the panel for maintenance purposes. Labels permanently attached to the panel shall identify each
relay and electronic card within the panel and adjacent to the equipment concerned.
All control relays shall be robust and firmly supported on their bases by use of retainer clips or
springs to avoid looseness that may occur due to vibration.
The cubicle shall be made of sheet steel not less than 2.0mm thick.
Devices and component shall be mounted and labeled according to number and function.
The control cubicles shall have terminal blocks for reception of cables cores (2.5 mm2) for
interfacing to the other plant control equipment. All wiring shall be of adequate cross section area
to carry prospective short circuit without risk of damage to conductors, insulation or joints. Wiring
shall be supported using an insulated system, which allows easy access for faults finding and
facilitate the installation of additional wiring. Ribbon cables cables with plug and sockets
connectors may be used for light current wiring. Plug and socket connector shall be polarized so
that they can be inserted into one another in the correct manner. All wiring shall be identified in
accordance with the associated schematic and/or wiring diagrams by means of discrete wire
numbers.
All internal electrical wiring for the control panels shall be neatly terminated. All wiring shall be
insulated with 600-volt grade oil-proof material. All connections shall be made at terminal blocks.
Terminal blocks shall be provided and rated not less than 600-volt, and shall be provided with
covers. At least 10 per cent extra terminals shall be provided in each group or terminal blocks.
Permanent identification of all terminals wires shall be provided.
A consistent system of wire numbering approved by the client shall be used throughout the
equipment.
1.4.6. Training:
A comprehensive training on the control system, operating software and control PLC algorithms
shall be conducted by the contractor to client Engineers to equip them with sufficient knowledge
on how to maintain and carry out future modifications on the control and SCADA systems. This
shall be done before the commencement of the factory acceptance tests.
A five (5) Tier training program is recommended as follows to help in attaining full technology
transfer to client Engineers:
f) Basic Training prior to project programs development to absorb the software general
concepts
g) Participation in project programs development during design(attachment to Contractor)
h) FAT participation testing
i) Participation in commissioning of the project program (attachment to Contractor)
j) Site training in the configured project programs
The contractor shall present a training proposal that shall be discussed and agreed upon with the
client during the preliminary design
A Typical arrangement of the panels is as in a sketch to be provided during the site visits.
2.
Communication Link between Wanjii Control Room and Tana Control Room.
The contractor shall establish a microwave point-to-point radio link between Wanjii Control room
and Tana Control room as specified below.
2.1. KenGen scope
KenGen shall avail existing communication masts at Wanjii Power Station and at Tana Power
Station for use by the contractor. The contractor shall establish, install and mount the necessary
equipment to share the mast with the existing equipment without interference. KenGen shall
provide power (AC) up to a distribution point, from where the contractor is expected to draw the
power for his equipment.
2.2. Microwave Point-to-Point Link
The contractor shall design, supply, install, test and commission a microwave point-to-point radio
link between the communication masts at Wanjii and Tana Power Stations. The masts are in use
by KenGen and the contractor must ensure that the equipment supplied and installed does not
interfere with any existing equipment or network.
There is a clear Line-Of-Site between the two stations.
The link shall be established on microwave frequencies in the 1.5GHz band. KenGen is utilizing
frequencies in the same band on the Kiritiri-Tana radio link and shall be responsible for payment
of the license fee to the Communications Commission of Kenya (CCK). The equipment supplied
must be robust to withstand the weather conditions in these locations. The preferred radio
equipment is Type Aprisa XE (or the latest model of the same) manufactured by 4RF
Communications Ltd of New Zealand.
The Specifications and configurations of the radios shall be as detailed in the table below.
3.
Parameter
4.
Requirement
Type & Model
Aprisa XE complete with Monitored Hot standby
Switch (MHSB) per pair.
Configuration
Hot standby Redundancy (1+1)
Power Consumption
Max 180Watts
Nominal voltage
-48Vdc, 4Amps
Input voltage range
40 to 60VDC
Channel Size
1.75MHz
Modulation
QPSK, 16QAM,32QAM,64QAM,128QAM
Frequency Band
1400MHz (range 1400MHz to 1520MHz)
Environment
Operating temperature up to 50° C
Humidity Maximum 95% non-condensing
Altitude Up to 2000 meters
Acoustic noise emission 59dBA (A-weighted sound
power level)
Mechanical
Height ≤8U
Width: 19-inch rack mount
ETSI Performance
Radio: EN 301 751, EN 300 630, EN 302 217 parts
1,2.1 and 2.2
EMI/EMC:EN 301 489 parts 1 & 4
Safety: EN 60950
Environmental: ETS 300 019 Class 3.2.
Interface Cards to be installed
QJET Quad E1/T1 Interface (1No.)
DFXO Dual Foreign Exchange Office Interface
(1No.)
DFXS Dual Foreign Exchange Subscriber Interface (
1No.)
Ethernet Interface
Receive Sensitivity ETSI
16QAM Modulation)
RJ-45x4 (Integrated 4-port switch)
(for -88dBM
Receiver Performance ETSI
Maximum input level -20dBm
Dynamic Range 58 to 87 dB (at 10-6 BER) depending
on modulation type and channel size.
Carrier to Interference ratio (C/I ratio) at 16QAM:
better than 20dB
System Gain ETSI at 16QAM, 119dB
channel size 1.75MHz
Transmitter Power ETSI (16QAM 17 to 31dBm
at 1400MHz frequency band)
Antenna Connector
N-Type female 50Ω
Configuration and Management
Embedded web server and /or SNMP accessed via
Ethernet interface or across link.
Test points (for RSSI)
Front panel test point for measuring the Received
Signal Strength Indicator (RSSI) voltage
The capacity of the link shall be 4E1s (approximately 8MBPS).
Power supply equipment for the radios at Wanjii and Tana shall comprise a 48Vdc, 30A redundant
19” Rack mount charger and Four (4 No.) 150Ah sealed re-chargeable batteries per site installed
in the same cabinet as the radios.
4.1. Last Mile Connection
The contractor shall lay optic fibre cable from the masts to the respective control rooms. The OFC
shall run in the ducting as a single run without jointing. The contractor shall lay a suitable ducting
on the ground running from the masts to the respective control rooms. The depth of laying the
ducting shall be suitable to avoid any damage and shall be approved by the employer. The route of
installation shall be clearly marked with concrete slabs suitably marked to indicate presence of an
underground cable. Inspection man-holes shall be placed along the ducting at distances of less
than 50m apart. The estimated length between the masts and the control rooms is:
Wanjii Mast to Control Room – 700m
Tana Mast to Control Room – 1000m.
Suitable media converters shall be installed to facilitate the last mile connection using the optical
fiber cable medium.
At the control room, the terminal equipment shall include a router configured with appropriate
interfaces, but at the minimum-Four (4 No.) T1/E1 and Two (2No.) 1Gigabit Ethernet interfaces.
The router shall be of Type Cisco 2900 series or the latest equivalent Cisco Router.
Ethernet switches supplied under this contract shall also be CISCO type. Their duty cycle shall be
industry rated so at to cope with the expected duty rate at site.
4.2.
Communications Equipment Room at Wanjii
Communications equipment room at Wanjii, shall be provided by the employer.
4.3. Training on Telecoms system
A comprehensive training on the Telecoms system shall be conducted by the contractor to client
Engineers to equip them with sufficient knowledge on how to maintain and carry out future
modifications on the system. This shall take not less than Five days and shall be done before the
commencement of the factory acceptance tests.
The contractor shall present a training proposal that shall be discussed and agreed upon with the
client during the preliminary design.
Two (2No.) Engineers/Technicians are proposed for the training.
5.
Tests and Commissioning
5.1. Factory Acceptance Tests
All components and assemblies of control & communications systems shall be tested in
accordance with the relevant IEC Standards to verify compliance with the requirements of
the Standards and Specification.
The control and protection systems shall have functional tests, signal checks and
redundancy systems failover tests shall be carried out at the factory before dispatch to prove
that all components operate together as a system and that all operating sequences and device
responses are satisfactory. It shall be the responsibility of the Contractor to provide test boxes
and other test equipment for sufficiently comprehensive tests.
All cubicles shall be subject to inspection during manufacture and on completion to verify
compliance with all the requirements of the Specification, including surface finish and
insulation resistance.
The client shall witness the factory tests.
5.2. Tests on Completion
General
The Contractor’s test schedules shall include comprehensive check lists for testing of the control,
protection, alarm and indication facilities.
5.2.1. Preliminary Tests
The preliminary tests shall include the following:
(a) Insulation resistance measurements at the specified voltages appropriate to the circuits and
equipment.
(b) Signal Test: Proof of correct connection and continuity of wiring for all control, protection,
auxiliary and alarm equipment in accordance with the overall diagrams as provided by the
Contractor.
(c) Functional tests to prove that all components operate together as a system and that all
operating sequences and device responses are satisfactory. It shall be the responsibility of the
Contractor to provide test programmes, test boxes and other test equipment for sufficiently
comprehensive tests.
(d) Tests of all indications, displayed quantities and analogue outputs to show such items
are within the accuracy limits specified.
5.2.2. Commissioning
Commissioning shall include the following:
(a) Demonstration that all controls, alarms and indications, including all sequences, displays and
reports operate correctly.
(b) A total of 50 starting, mode change and stopping sequences covering all the sequences to be
provided. During the specified 50 sequences required to be performed by each of the Units,
the whole of the equipment shall perform without adjustment.
(c) Sequence failure tests shall be carried out for each step in both start up and stopping
sequence.
(d) Remote monitoring and control of all Wanjii power plants and associated works from Tana
power station Control Centre.
(e) The Reliability Test Period.
ANNEX 4: - EXCITATION SYSTEM
1.
Technical Specifications: Static Excitation Systems
1.1. Type and description.
The Excitation equipment shall be designed to ensure continuity of operation under all working
conditions and to facilitate inspection, maintenance and repairs. All reasonable precautions shall
be taken in the design of equipment to ensure safety of personnel concerned with the operation
and maintenance of the equipment.
All electrical components shall be adequately rated for their most onerous duty and the specified
ambient temperature. Due account shall be taken of any heat generated by the equipment therein
and the components shall be appropriately selected, rated as necessary to suit the most onerous
operating temperature within the panel.
The contractor shall design and supply a Static excitation system with excitation transformer. This
comprises but not limited to:
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Excitation control
Automatic Voltage Regulator with adjustable PID controller (Automatic mode).
Dual Thyristor converter bridges in hot standby operating mode
Field suppression equipment
Rotor overvoltage protection equipment
Thyristor overvoltage protection
Static Excitation protection equipment
Under-excitation and Over-excitation limiters
Reactive Power influence (droop or compensation)
Rotor earth-fault protection (alarm and trip stages)
Field breaker
field flashing breaker
Voltage matching function
Excitation transformer overcurrent protection relay (alarm and trip stages)and any other
protection system
Excitation Transformer and associated equipment.
The control and instrumentation system shall include but not limited to:
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Interfaces with other control equipment (i.e. turbine, generator etc)
local instruments for monitoring excitation system and excitation transformer parameters
Interfaces with the protection equipment
Devices/relays required for the tripping of the excitation system
Hardwired manual controls; push buttons with integral lights, control relays, selector
switches, timers, raise/lower switches, discrepancy switches, etc.
Connection of all unit control and instrumentation equipment/devices provided to the new
excitation system with excitation transformer Panels.
Power, voltage and current Transducers
All additional items required for the safe and efficient operation of the excitation system.
1.2. Field flashing
A field flashing system shall be included in the excitation system. This shall draw power from the
110Vdc battery bank being supplied under this contract.. A suitably rated MCB for switching the
above mentioned supply for field flashing shall be provided in the excitation equipment. The circuit
shall be designed to supply about 20% of the no-load field current.
1.3. Cooling air system
Forced cooling of the Thyristor Convertor should be provided by AC driven motor fans, monitored
by an air-flow relay. One AC- motor shall be provided for each of the Thyristor bridges. Thyristor
heat sinks should be arranged to form a central duct through which the cooling air may pass
leaving all of the small components and electrical insulation in relatively still air and less prone to
the accumulation of dust.
Suitable removable air intake filters shall be included on the cubicle housing the Thyristor
converters.
The fans shall be powered by the excitation transformer (main supply) and station auxiliary supply
through a selector switch. The station auxiliary supply shall only be used in testing the fans under
static conditions. The fans shall be protected by use of well rated MCCBs.
The fans control shall be designed to run automatically with execution of excitation command. The
fans should also have a manual mode, whereby the fans ON/OFF commands shall be initiated from
both push buttons (with LED indications) mounted on the excitation panel and on the HMI.
1.4. Thyristor rectifiers
The Thyristor converter shall consist of dual Thyristor bridges. The bridges shall operate in hot
standby mode. Design and construction of the two bridges shall allow fault finding, maintenance
and testing to proceed on one rectifier while the other remains in operation (online). The design
shall satisfy all required operating conditions.
Failure in one rectifier shall generate an alarm and changeover to the standby but failure in both
rectifiers shall result in a trip. The dual rectifier configuration shall ensure a smooth change – over
from the main rectifier to the standby rectifier.
The temperature of the thyristor converter shall be monitored by suitable resistance temperature
detectors, mounted on the heat sinks. Temperature alarms shall be provided.
The rectified bridge full load output shall be rated at a minimum of 1.2 times the maximum
excitation current at ceiling excitation voltage. All equipment should be fully segregated by suitable
insulation barriers to reduce the possibility of short circuits.
An approved monitor/detector (conduction of current) circuit shall be fitted on each of the
rectifier bridge to provide an alarm when the bridge fails. Should both bridges fail a trip command
shall be issued. The alarm and trip shall be enunciated in the excitation system. Spare alarm and
trip contacts shall be wired to the terminal block.
DC millivolt ammeters driven by suitable shunts shall be provided to indicate the DC current from
each rectifier bridge. These meters shall be mounted on the front of the cubicle housing the
thyristor converters.
1.5. Excitation power supply:
The excitation Control voltage shall be 24Vdc supply. Dual redundant power supplies shall be
provided and shall draw power from both DC and AC sources as follows below:

DC supply -110 Volts Nominal [Range +15 % /-20%]
AC supply - 240 Volts 50Hz Nominal [Range +5 % /-10%]
Failure of one source of supply shall not affect the operation of the excitation equipment. An output
contact indicating failure of any of the power source shall be provided. The primary and secondary
voltages of the power supply shall be galvanically isolated.
1.6. Automatic voltage control(AVR)
The automatic voltage control (AVR) shall be the normal mode of operation of the excitation
system.
The AVR shall include the following:
The Control voltage of the AVR shall be drawn from the 24Vdc dual redundant power.
Failure of one source of supply shall not affect the operation of the AVR equipment. An output
contact indicating failure of any of the power source shall be provided.
The AVR control algorithm shall have a PID response with two adjustable lead-lag filters to
optimize the dynamic behaviour of the machine.
Adjustable reactive and active power influence shall be implemented into the control algorithm to
ensure stable parallel operation with the network and /or other generators.
Any power supply failure or detectable component failure in the AVR shall result in automatic and
instantaneous changeover to manual mode.
The AVR shall include the following limiting functions: V/Hz – Limiter,
 Maximum field current limiter,
 Under-excitation P/Q – based limiter,
 Stator current limiter,
 Minimum field current limiter
 Overvoltage limiter
Field current limiter, instantaneously and delayed acting with an inverse time characteristic, shall
be provided to protect the generator field against the excessive sustained output from the Excitation
System.
Stator current limiter, delayed acting with an inverse time characteristic in the overexcited and
instantaneously acting in under-excitation operation mode, shall be provided in order to keep the
stator current below a set value and prevents the stator windings from the thermal overloads.
Minimum field current limiter shall act instantaneously and shall be provided to prevent
overheating of the rotor.
All limiter functions should be integral part of the automatic voltage regulation program. They
interact with the overall excitation control system in such a way that the operation of the generator
is within its capacity limit.
The generator terminal voltage shall be adjustable over the range of 90% to 110% of rated voltage
under no-load operation.
A reactive current compounding circuit shall be included to provide reactive load sharing during
parallel operation. The compounding characteristic shall be adjustable.
Low excitation or an MVAR limiter shall be included to prevent the regulator reducing the
generator excitation below safe limits under loading power factor conditions. This equipment shall
be arranged to provide an alarm and interlock in the event of extremely low excitation control.
The voltage regulator shall be capable of controlling the field under the following conditions:
Maintain generator voltage under normal operating conditions within 0.5% without
hunting

Maintain generator voltage under load rejection or up to 150% over speed within 5% of
its preset level.

Maintain generator voltage under maximum overspeed within 10% of its present level.

Continuous stable operation of the generator under line charging conditions
Voltage control shall be accomplished by the continuous comparison of the average three phase
voltage of the generator with a reliable and stable reference voltage source provided in the control
system.
A power system stabiliser shall be provided for protection against electromechanical oscillations
from a system disturbance. The device shall operate to supplement the voltage regulating action
by adding a controlled signal into the Excitation System input.
The ratio of voltage to frequency limiting device with adjustable setter shall be provided to protect
against over-excitation due to frequency drop.
Provision shall be made for normal field de-energization with a crow bar and rapid field demagnetization (via voltage inversion in a full thyristor bridge) whenever the generator lock-out
relays/trip relays are operated or serious excitation faults occurs.
The following monitoring and protection functions shall be integral part of AVR’s program: PT-failure monitoring,
 Monitoring of synchronization voltages for control pulses,
 Self test of electronics
 Converter current monitoring
1.7. Manual voltage control(field current regulator (FCR))
The field current regulator (FCR) shall be provided to regulate the field current from about 20% of
the rated generator terminal voltage to the rated voltage for generator operation at the rated
output, rated power factor and rated frequency, and 110% of rated voltage. Provision in this mode
shall be made to allow special tests namely:-
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Excitation commissioning test- thyristor firing checks,
Generator open circuit and short circuit characteristic testing,
Generator Electrical Protection verification.
The manual control shall also incorporate EFCR (Emergency Field Current Regulation)
mode
Maintenance purposes.
A key operated selector switch shall be used to switch from AVR mode to manual mode and vice
versa. However, if a fault occurs in the AVR during normal operating mode, the excitation shall
switch over to manual mode automatically and generate an alarm to annunciate AVR trip to
manual mode without tripping the unit.
The manual mode (FCR) shall always follow the position of the AVR setting point. If a deviation
occurs in the reference, an alarm shall be generated and annunciated in the unit control board.
1.8. Excitation control PLC
The excitation interface to plant control and other systems shall be via a control PLC.
All external commands from the automation system shall be connected to the control
programmable logic controller (PLC) system.
The excitation control PLC shall be interfaced to the AVR and other control devices in the excitation
system.
All the external commands and annunciation alarms between the excitation system and unit
control PLC shall be via this PLC.
Each Input/Output signal shall have a unique identification tag number and description. The
excitation signal list showing the unique identification tag number and description shall be
approved by the client.
The excitation shall have two control levels. These are local and remote control levels. A key
selector switch shall be installed to change from one level of control to the other.

Local control level: In this mode, the excitation shall be operated at the local excitation
panel. Only commands from the excitation HMI panel or local push buttons shall be
accepted.
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Remote control level: In this mode, only commands from the unit control automation panel
shall be accepted by the excitation system. However, trip signals shall not be interlocked
through this selection.
The excitation Equipment shall be programmed by high level programming language that is userfriendly. Windows pull down menus and mouse control interface software shall be provided.
1.9. Supervision of excitation system Controller
Comprehensive self testing and self diagnostic facilities are required to be included in the excitation
equipment.
The monitoring of the excitation system controller shall include but not limited to the following
functions.
The Contractor shall provide details of the following facilities offered: Correct application program scanning check,
 Memory integrity checks.
 Validity of data exchange between memories, processing units and I/O modules.
 Power supply check
 Main processor unit status check,
 I/O channel integrity check.
 Error message display
 Integral supervision functions
 Other self test and diagnostic execution details.
 Self monitoring of the processor
 Process connections
The Contractor shall also provide details of the facility proposed for reporting the self test and
diagnostic message. Output contacts shall be provided for external fault indication.
1.10. Voltage matching function/ Pre-synchronizing control.
A Pre-synchronizing control system shall be provided. Using the grid voltage as a reference, it shall
be designed to control the generator terminal voltage to a level equivalent to the grid voltage so
that synchronization takes place smoothly.
In the event that this system is faulty, the excitation shall be designed to build the generator
terminal voltage to 11KV level. The excitation shall then receive commands for RAISE/LOWER
from the synchronizing equipment to balance the generator terminal voltage to the grid voltage.
1.11. Peripherals and Software Package
All peripherals to the excitation Equipment, such as programming units shall be supplied as part
of this contract. The programming unit shall operate at 240V, 50Hz. The software package with
the necessary license and the programs for all the PLCs, HMI used in the excitation system and the
relay software used shall be supplied as part of this contract.
The Contractor shall provide details of the facilities to be included. This shall cover the method of
programming program storage, program loading and program documentation.
Any modifications to an existing program shall be protected by password or key-switch security.
The portable programming units shall be capable of providing the facilities for local excitation
fault finding, self diagnostic facilities and commissioning. Details of the programming, de bugging,
maintenance, fault finding and diagnostic facilities shall be provided by Contractor.
. The software will display the signal values/level in the excitation on the screen of the portable
device in an analogue manner.
The software will provide functions to modify, store, compare the running program with file, test
and for graphical documentation of the program.
A hardcopy of the software program including all the parameters setting and range shall be
provided in the documentation.
The operating software and the programs shall also be provided in a CD form for future loading
into another PC.
Cable and adapter interface required to connect the PC to the excitation equipment PLCs, HMI
shall be supplied as part of this contract.
1.12. Training:
A comprehensive training on the excitation, operating software and control PLC algorithms shall
be conducted by the contractor to client Engineers to equip them with sufficient knowledge on
how to maintain and carry out future modifications on the excitation system.
A five (5) Tier training program is recommended as follows to help in attaining full technology
transfer to client Engineers:
k) Basic Training prior to project programs development to absorb the software general
concepts
l) Participation in project programs development during design(attachment to Contractor)
m) FAT participation testing
n) Participation in commissioning of the project program (attachment to Contractor)
o) Site training in the configured project programs
The contractor shall present a training proposal that shall be discussed and agreed upon with the
client during the preliminary design
1.13. Local Operator panel with HMI screens
The local control of the excitation system shall be through an operator panel (shall be touch screen)
industrial PC flush mounted on the excitation panel. This shall be via function keys on the
industrial PC screen or control buttons developed on the industrial PC operator panel.
The most important functions shall be placed directly at function keys, which should be common
regardless of choice of window. Some of the function keys shall be used to set direct commands to
process.
Apart from the function keys being provided for in the operator panel, specific selector switches
and push buttons mentioned in this document shall be provided to make the system operational in
case the operator panel is faulty.
The screens that shall form part of the requirement to interface and display field data are but not
limited to:  Main page: This screen shall contain the generator line diagram with animated symbols for
the field breaker, generator breaker and the common bus bar. It shall also indicate day,
date, time and the unit number and shall be used to log into the system through a password.
 Operational data: This screen shall contain most important measurements, operational
mode and set points for all different states.
 Trends screen: In this screen, the operator shall be able to carry out a real time trending of
line graphs of all the analogue signals.
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Excitation Limiter list: This screen shall contain all the excitation limiters together with
their set points.
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Temperatures screen: All excitation system and excitation transformer temperature
measurement shall be displayed on this screen.

Alarm list: All the alarms shall be indicated in this screen. Alarms/warning shall be flashing
and yellow in colour while active trip signals shall be red in colour and flashing.
Alarms/warnings that have normalized shall turn into green colour awaiting
acknowledgement. This screen should also contain a button for alarm/trip
acknowledgement and alarm reset.
It shall be possible to filter the alarm and trip list with date and time. The alarm/trip list
shall be time stamped by the PLC and shall appear in a chronological order as they occurred.

Each alarm shall have an identification tag number, the alarm description, time and date
of occurrence.
Event logs: This screen shall contain all system events including alarms and trip signals.
These shall be time stamped in the order of occurrence. It shall be possible to filter the event
list with date and time. The event list shall be time stamped by the PLC and shall appear in
a chronological order as they occurred.
Each event shall have an identification tag number, the alarm description, time and date of
occurrence.

Parameter display on all Human Machine Interfaces: All analogue parameters associated
with the excitation system and the generator parameters displayed on all the excitation
system HMIs shall be displayed in their respective units of measure.
1.14. Excitation system protection:
The protection and alarms shall be provided for, but not limited to the followings
conditions:1)
PROTECTION/trip signals: Overcurrent, short circuit
 Field flashing ,failure
 Generator speed, low
 Rotor overvoltage
 Excitation transformer over temperature
 Rotor earth fault stage 2, impedance less than 5K Ohms to ground
 Loss of excitation
 Two (2) or more rectifier protection fuses, blown
 Failure of both rectifiers.
 Failure of both power supplies.
 Rectifier cooling failure
These signals shall be interfaced to trip/shutdown unit via the unit control board.
2)
ALARMS/warnings: One (1) rectifier protection fuse, blown
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Voltage setter for AVR, fault
Voltage setter for FCR fault
Excitation transformer temperature high
Over-excitation limiter operated
Under-excitation limiter, operated
Volts per hertz limiter
Power system stabilizer, fault
Automatic reactive power regulator fault
Rotor Earth fault stage 1 , impedance less than 80K Ohms to ground
Generator actual voltage (Voltage from generator voltage transformer) failure
Rotor Overvoltage
110Vdc Auxiliary supply failure
AC supply failure
Voltage supply supervision: Excitation transformer temperature protection.
Thyristor converter temperature high
Change over to manual mode (Automatic mode failure) Fault
1.15. Rotor ground fault protection device
An Approved active rotor insulation monitor devices shall be provided to indicate the active
insulation level, to provide an alarm level (<80K ohms) and trip level (less than 5K ohms).
Provision shall be made for isolation of the rotor insulation monitor device during maintenance of
main rotor circuit.
1.16. Parallel operation and isolated operation.
The excitation system shall be capable of supporting the unit while operating in both parallel mode
(synchronized) and in isolated mode (unit not synchronized but running to supply local loads).
1.17. Panel construction
The Excitation system with excitation transformer Panels shall be of rittal standard, floor-mounted
and free standing construction for indoor installation with cable entry from the bottom. Ventilation
points shall be provided with suitable removable air filters to prevent the ingress of dust and
insects.
Cubicle size and colour shall match the Unit Control cubicles.
The excitation cubicle shall be of tropical design and to IP54 Protection code of practice according
to IEC529.
The cubicle shall be fitted with lifting eye bolts which shall be removed after installation.
All metal parts other than those forming part of an electrical circuit shall be connected in an
approved manner to separate earth bars running along the bottom of the panel. The metal cases of
all instruments and the like shall be connected to the copper earth bars by conductors of not less
than 2.5sq mm or by other approved means.
Doors shall be fitted with handles and locks [key operated]. The cubicle shall contain internal
power sockets. Door operated cubicle internal lighting shall be provided.
All instrument and control devices shall be easily accessible and capable of being removed from
the panel for maintenance purposes. Labels permanently attached to the panel shall identify each
relay and electronic card within the panel and adjacent to the equipment concerned.
All control relays shall be robust and firmly supported on their bases by use of retainer clips or
springs to avoid looseness that may occur due to vibration.
The cubicle shall be made of sheet steel not less than 2.0mm thick.
Devices and component shall be mounted and labelled according to number and function.
The excitation Equipment cubicle shall have terminal blocks for reception of cables cores (2.5
mm2) for interfacing to the other plant control equipment. All wiring shall be of adequate cross
section area to carry prospective short circuit without risk of damage to conductors, insulation or
joints. Wiring shall be supported using an insulated system, which allows easy access for faults
finding and facilitate the installation of additional wiring. Ribbon cables with plug and sockets
connectors may be used for light current wiring. Plug and socket connector shall be polarized so
that they can be inserted into one another in the correct manner. All wiring shall be identified in
accordance with the associated schematic and/or wiring diagrams by means of discrete wire
numbers.
All internal electrical wiring for the excitation cabinet shall be neatly terminated. All wiring shall
be insulated with 600-volt grade oil-proof material. All connections shall be made at terminal
blocks. Terminal blocks shall be provided and rated not less than 600-volt, and shall be provided
with covers. At least 10 per cent extra terminals shall be provided in each group or terminal
blocks.
Permanent identification of all terminals wires shall be provided. A consistent system of wire
numbering approved by the client shall be used throughout the equipment
1.18. Cables and cabling works
The contractor shall interface the excitation system via hard wired connections to the unit control
board to be supplied under this contract.
All the cables shall be of stranded copper cores, shielded and steel armoured. Cables shall be well
labelled at both ends. All necessary cable support systems shall be provided.
The contractor shall provide all necessary materials required for theses works.
1.19. Inspection and testing
1.19.1. Factory Tests
All components and assemblies of Excitation system with excitation transformer shall be
tested in accordance with the relevant IEC Standards to verify compliance with the
requirements of the Standards and Specification.
The client shall witness the factory tests.
The factory tests for the Excitation system with excitation transformer shall have but not
limited to: functional tests, alarm test, converter firing tests, different modes regulation
tests, no-load & load condition tests, limiters tests carried out at the factory before dispatch
to prove that all components operate together as a system and that all operating sequences
and device responses are satisfactory. It shall be the responsibility of the Contractor to
provide test boxes and other test equipment for sufficiently comprehensive tests.
All cubicles shall be subject to inspection during manufacture and on completion to verify
compliance with all the requirements of the Specification, including surface finish and
insulation resistance.
The contractor shall submit a detailed factory acceptance tests program indicating all the
tests that shall be carried out to the client for review and approval.
1.19.2. Site Tests
The Contractor’s test schedules shall include comprehensive check lists for testing of the
operation, alarms and indication facilities.
The preliminary tests shall include but not limited to the following:
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Insulation resistance measurements at the specified voltages appropriate to the
circuits and equipment.
Signal Test: Proof of correct connection and continuity of wiring for all control,
protection and alarm equipment in accordance with the overall diagrams as
provided by the Contractor.
Functional tests to prove that all components operate together as a system and that
all operating sequences and device responses are satisfactory. It shall be the
responsibility of the Contractor to provide test programme and test equipment for
sufficiently comprehensive tests.
Tests of all indications, displayed quantities and analogue outputs to show such
items are within the accuracy limits specified.
Transformer tests: Insulation resistance measurements, vector group, ratio test,
protection tests etc.
The Tests on Completion shall include the following:
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Demonstration that all controls, alarms and indications operate correctly.
operating Modes change
AVR changeover to manual
Rectifier changeover
Demonstration that all Emergency stops and Shutdown (both excitation external
and internal Trips) controls operate correctly.
The Reliability Test.
1.20. Excitation spares spare parts
The contractor shall provide but not limited to the following spare parts. The contractor shall
supply any other spare part that may be considered useful due to his design.
 20% of each type of control relay
 20% of each bi-stable relay
 20% of each type of control timer relay
 Four trip relay of each type
 Four indicating instrument of each type
 20% of indicating lamps (LEDs) of each type
 Two power supplies of each type
 Two power supply supervision relay of each type
 four MCCBs of each type
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Two Switches of each type (push-button, selector switch, discrepancy switch, keyswitch, etc)
 One Electric power transducer
 One PLC CPU of each type loaded with the appropriate software and program
 One HMI module of each type loaded with the appropriate software and program
 One PLC input/output card of each type.
 AVR cards. One per type
 Excitation transformer temperature sensors (two)
 Thyristor temperature sensors (two)
 Eight thyristors
 Ten thyristor fuses
Note: Where percentages are used the fractions shall be rounded upwards.
2.
EXCITATION TRANSFORMER
A three phase excitation transformer shall be supplied to step down the 11KV output of the
generator voltage and feed the excitation rectifiers. The transformer shall be correctly rated
to carry out maximum probable Excitation current required depending on the generator
rating.
The transformer shall be of the dry type, copper winding, suitable for indoor installation;
manufactured in accordance with IEC 60076-11 wound for a primary voltage equivalent
to the generator rated voltage and rated to suit the rectifier equipment. It shall be complete
with all necessary cable boxes, primary current transformers, primary bushings, skid
underbase, rating and diagram plates, lifting lugs and earthing terminal, all contained in
sheet steel cubicle housing. Transportation rails shall be incorporated for the purpose of
transporting the transformer to and from the mounting position.
The design of the transformer insulation throughout shall be suitably coordinated for the
specific insulation level to minimize the effect of any impulse surge voltages.
The transformer shall be adequately protected against over current and temperature rise.
The temperature of the transformer shall be monitored by use of both PT100 and a capillary
dial gauge. The capillary dial gauge shall be flush mounted on the excitation panel to
display the transformer temperature. This shall have heavy duty contacts with set levels for
alarm and trip signals. These contacts shall be enough for annunciation on the excitation
alarm window. Spare alarm and trip contacts are to be provided and wired to the unit
control board.
The PT100 temperature sensors shall be connected to the excitation PLC and unit control
board system for real time temperature monitoring.
The connection to the transformer shall be tapped from the outgoing generator terminals.
The contractor shall supply and install connection cables/copper bars that are adequately
rated and supported with insulating material. Current transformers for over current
protection schemes shall be installed.
The excitation transformer and its auxiliary equipment shall be housed. The housing
enclosure shall be well ventilated to allow maximum cooling of the transformer.
ANNEX 5- PROTECTION RELAYS AND 11KV INDOOR SWITCHBOARD
TECHNICAL SPECIFICATION: PROTECTION SYSTYEMS
1. General Specifications
The general specifications for the electrical protection systems are:
 The protection relays shall be numerical relays based on microprocessor technology. The
relays supplied shall have fault recording facilities for use during analysis of system
disturbances. The relays should also have measurement facilities.
 The relay programming & testing software and the fault analysis software shall be supplied
in a portable computer (laptop) and shall be handed over to the employer. Any additional
tools (e.g. communication cable) required for programming and testing of tall protection
relays , including the necessary licenses, shall also be supplied. The specific features of the
laptop shall be included in the tenderer’s bid and shall be subject to approval by the
employer.
 The relays shall have an LCD display for display of measurements, settings, alarms and
trips. They shall also have LED indications which shall be configurable for annunciation.
 The relays shall be supplied with 110VDC from the station batteries. The input and output
contacts shall be of robust construction to withstand harsh operation conditions. All trip
contacts shall be latched contacts.
 The individual functions shall be hardwired to the unit PLC for generator related trips and
to the common plc for the generator transformer, station transformer and feeder related
trips. This shall be for purposes of annunciation. Additionally, a grouped alarm from each
protection relay shall be hardwired to Unit auxiliary panel for indication on the alarm
fascia.
 The relays shall be flush mounted to the panels. There shall be test terminals blocks for use
in testing of the relays. Such test blocks shall isolate the field inputs and allow for testing of
the relays without isolation of wiring to the relays. Any accessories required for testing shall
be supplied together with the relays.
 The protection relays for the generators and transformers shall be housed in a minimum of
two free standing panels. The actual relay and panel arrangement shall be approved by the
employer.
 Feeder protection relays shall be located in one free standing panel. This shall include the
test terminal blocks and associated auxiliaries. A set of relay programming software, fault
analysis software, plugs for test terminal blocks and any related accessories necessary for
programming, testing and commissioning of feeder protection relay must be supplied, in
addition to the previous requirements. This set of kit shall be for use by the grid operator
(Kenya Power).
 The contractor shall be responsible for determination of relay settings for generators,
generator transformers, station transformers and feeders’ protection. The contractor shall
provide the functions listed below as a minimum. Where the relay supplied contains more
functions than the list below, the contractor is expected to implement the extra functions
into the protection schemes.
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The contractor shall also be responsible for review of relay setting at the end of the
transmission lines located at 11/33kV substation at Tana Power Station. Where such a
review may require additional features to the existing ones, the contractors shall advice the
client and supply accordingly at no extra cost to the client.
The trip matrix from the protection relays shall be coordinated to allow for fast clearance
of the faults with proper equipment/system isolation principles. Such a matrix shall be
provided for approval by employer.
The current transformers and voltage transformers to be used for protection have already
been specified in other sections of this document.
2. Generator Protection
 The following generator protection functions shall be provided, preferably in one
multifunction protection relay,
o generator overvoltage
o generator under voltage
o generator over frequency
o generator under frequency
o instantaneous and time dependent over current
o 95% stator earth fault
o Generator reverse power
o Percentage Differential Protection
o Negative Phase Sequence
o Breaker Failure Protection
o Thermal Protection (Stator RTDs)
o Under Excitation
o Breaker Failure
o Trip circuit supervision
 The over current protection of the excitation transformer shall also be provided as part
of the generator protection. The contractor may include the function as part of the
generator protection relay or may provide a relay for this function.
 The relays shall have a minimum of three RTD inputs.
 The following trip outputs shall be provided as a minimum:
o Governor Trip
o Excitation Trip
o Generator Circuit Breaker Trip
o Unit PLC.
o Bus coupler
3. Generator Transformer Protection
 The following protection functions shall be provided
o Transformer differential
o Neutral Voltage Displacement
o Restricted Earth Fault
o Instantaneous Earth Fault
o Instantaneous and time dependent over current
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o Voltage Controlled Over current
o Breaker Failure
o Over fluxing
o Trip circuit supervision
The following trips should also be provided for as inputs
o Winding and Oil Temperature Trips
o Pressure Relief Device Operated Trip
o Buchholz Gas Trip
The relays shall have a minimum of three RTD inputs.
The differential protection zone of the transformer shall cover the zone up to the high
voltage terminals of the station transformer.
The following trip outputs shall be provided as a minimum:
o Generator transformer Breaker (SF6 CB)
o Generator Circuit Breaker Trip to each generator
o Bus coupler trip
o Unit PLC.
4. Station Transformer Protection
 The protection shall include the station transformer and the auxiliary feeder transformer.
 The following functions shall be provided for
o Instantaneous and time dependent over current
o Instantaneous earth fault.
o Breaker failure
o Trip circuit supervision
 The following trip outputs shall be provided as a minimum:
o Generator transformer Breaker (SF6 CB)
o Generator Circuit Breaker Trip to each generator
o Bus coupler trip
o Unit PLC.
5. Feeder Protection
 Feeder protection shall be provided for the protection of Tana 1, Tana 2 and Mesco feeders.
 The following functions shall be provided for:
o Instantaneous and time dependent over current
o Instantaneous earth fault
o Breaker Failure
o Trip circuit supervision
 The following trip outputs shall be provided as a minimum:
o Generator transformer Breaker (SF6 CB)
o Feeder Breaker (SF6 CB)
6. Lock-Out Relays
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There shall be lock-out relays for the generators, generator transformers, and the feeders.
These relays shall issue trips to the trip coils of the circuit breakers after receiving trips for
the control system and the protection relays.
 The relays shall have a hand and automatic reset mechanism. They shall also have LED for
status indications.
 The lock-out relays shall have a minimum of 10 heavy duty contacts.
7. 11KV Switchboard
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There shall be a new switchboard established for the connection of the following:
o Four generator incomers
o Two transformer feeders
o One bus coupler
o One station transformer feeder specified under annex 6 clause 2.
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The switchboard manufacture shall be in conformance to international standards, among
them IEC 60056, 60298, 60694 and 622271 (applicable parts). The design and
operational philosophy of the 11kV switchboard must be submitted for review and
approval by the employer before any assembly or manufacturing can commence.
The switchboard shall be in two sections, with laminated copper busbars of a nominal
rating of 11kV, 1250A (minimum), 3-phase and 50Hz. The busbar shall be rated to carry
the full load of the station without violating the temperature rise limitations of the
switchboard.
The contractor shall determine the short circuit current levels at the various points of the
system. The short circuit rating of the busbar and switchboard equipment shall be
coordinated with the determined short circuit levels.
Proper insulation coordination shall be done for all equipment installed in this project as
per IEC 60071-1 and IEC 60071-2.
The breakers supplied shall be vacuum circuit breakers (VCBs) rated at 11kV, 630A, 3phase 50Hz. The breakers shall be withdrawable for isolation purposes. The exposed busbar
should be covered with lockable safety shutters whenever the VCB is withdrawn. The
switchboard should have integral earthing on all the feeders that shall be applied whenever
needed.
The switchboard shall have provision for bottom entry of power and control cables.
Termination of the power and control cables shall be of good engineering workmanship.
All control cable terminations shall be placed in an easily accessible location, preferable in
the low voltage compartment of the panels. The contractor may consider establishing a
marshalling kiosk/panel where it is considered that the location of the terminations is not
safe enough for staff carrying out maintenance works.
The switchboard apparatus shall be supplied with 110VDC supply from the 110VDC
station batteries. Each circuit breaker shall have two trip coils with independent and
duplicated circuits and one close coil. There shall be trip circuit supervision of the breakers
achieved by use of protection relays.
Each incomer or feeder shall have voltage and current transformers for protection,
metering and instrumentation as may be required. The VTs for Neutral Voltage
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Displacement (NVD) protection of the generator transformers shall be located on the
Transformer feeders before the respective breakers.
There shall be two busbar VTs – one on each bus-section. The VTs shall have two cores each
for synchronizing the generators to the bus-section.
The Voltage transformers (VTs) should be fixed with withdrawable fuses on the primary
and secondary voltage sides. The VTs shall be rated at class 3P, 11000/√3/110/√3 VAC,
50Hz and shall have the following cores:
o Metering core -Class 0.5
o Protection core – class 3P
The contractor shall determine the appropriate rating and specification of the Current
Transformers (CTs) to be mounted in this switchboard. The CTs shall have a minimum of
the following cores
o Metering and Indication – Class 0.5
o Differential Protection core for transformer or generator protection as appropriate.
o Over-current Protection core
There shall be local indication of one phase voltage and one phase current by use of analog
devices (of size 96 X 96 mm) on each incomer or feeder.
Indications that are local to the switchboard shall include
o ON, OFF, TRIP by use of LED lamps.
o ISOLATED, IN TEST and IN-SERVICE positions.
There shall be LOCAL/REMOTE selection switch to allow for remote closing of the breaker
via the SCADA/PLC system or from the Unit Auxiliary Panel.
Factory Acceptance Tests
Protection panels including relays, and metering equipment shall be subjected to
routine and type tests at the manufacturer’s works in accordance with the relevant
International Electrotechnical Commission (IEC) Standards or equivalent.
All protection relays and associated equipment shall be tested in accordance with the
requirements of IEC 60255.
Type test reports shall be accepted in lieu of type testing; provided that the
Contractor submits in advance, certified type test reports for tests on similar
equipment carried out by an independent accredited testing authority.
Tests on Completion
General
Test sets and test equipment required for testing the protection relays and metering
equipment shall be provided by the Contractor. All protection relays and associated
equipment shall be tested in accordance with the requirements of IEC 60255.
Site Tests
The following inspection and tests shall be carried out at site:
(a) Visual inspection
(b) Insulation resistance test
(c) Wiring checks and loop resistance
(d) CT polarity and magnetisation curves
(e) Secondary injection tests on protection relays
(f) Primary injection tests of relays and circuit wiring
(g) Alarm and trip testing
(h) On-load tests with simulation of faults
(i) Operation and accuracy of all meters shall be verified
ANNEX 6 –SWITCH YARD AND TRANSFORMERS
POWER EVACUATION FROM THE STATION.
The proposed single line diagram for the power flow is shown as drawing 1.
The power generated from the four generators shall be evacuated through Tana 1 and 2 feeders to
an 11/33kV substation located at Tana Power Station.
One generator on Mathioya River and one generator on the Maragua River shall be connected to
one section (section 1) of the 11kV Switchboard, while the remaining generators shall be
connected to the other section (Section 2) of the switchboard. There shall be a busbar coupler in
this switchboard which shall be designed as Normally Open circuit breaker. The switchboard shall
consist of vacuum breakers, current transformers, voltage transformers, earthing switches and
other associated equipment for the incomers and feeders.
The output of the generators shall be connected to the 11kV switchboard by use of XLPE cables.
From the switchboard, Section 1 shall be connected via XLPE cables to generator transformer 1
located in the switchyard. Section 2 of the switchboard shall be connected via XLPE cables to the
generator transformer 2 installed in the yard. The XLPE cables shall be terminated on the
transformer cable box. Each Transformer shall be sized for 2 Mathioya machines and one
Maragua machine.
The switchyard shall have two generator step-up transformers outdoor circuit breakers (SF6 type),
Disconnector switches (isolators), a bus-coupler connecting the two sections of the 11kV busbar
and a step-down transformer supplying auxiliaries board in the power house.
The power output from the two transformers shall be connected to an 11kV overhead busbar
serving Tana 1 and Tana 2 feeders. There shall be an isolator on this busbar which shall mainly be
operated in an open position. There shall be circuit breakers and isolators for the Tana 1 & 2
feeders. The contractors scope shall extend past the line breakers, isolators, VTs and CTs upto the
take off of the Tana 1 & 2 feeders.
On the star side of each transformer, there shall be overhead conductors connecting the
transformer to an overhead 11kV busbar via an outdoor SF6 breaker and an isolator.
The insulation level for all switchgear and equipment delivered under this project shall be guided
by IEC 60071-1 and shall be as follows:
Nominal Voltage Rating of the
Equipment, Ur
11kV
Highest equipment voltage, Um
12kV
Standard Short-time power frequency withstand
voltage, RMS value
Standard lighting impulse withstand voltage,
peak value
28kV
75kV
1. GENERATOR TRANSFORMERS
The generator transformer shall conform fully to the requirements of IEC 60076
The transformers shall be outdoor type, three-phase, single unit oil-immersed step-up generator
transformer.
The transformer shall be suitable for continuous outdoor operation in tropical latitudes with the
following atmospheric conditions: Altitude: 1200m Above Sea level, Heavy humidity of up to
60% and Ambient temperatures 45°C max and 10°C min.
1.1 Rating
Transformers shall be rated as follows:Each Transformer shall be sized for 2 Mathioya machines and one Maragua machine. Each
section shall connect one machine from Mathioya river and one machine from Maragua river
with a bus coupler to connect the two sections.The generator transformers shall be rated for
50Hz, YNd1 vector group. The star winding shall have an On Load Tap changer with seven (7)
taps with a voltage variation of +/- 1.5% from nominal tap. The contractor shall determine the
nominal tap rating of the transformer taking into consideration the existing transmission lines
evacuating power from Wanjii. The impedance rating of the transformer shall be 10% and
within tolerances as specified in the IEC 60076 standard.”
1.2 Cooling system
The transformers shall have an Oil-Natural-Air-Forced cooling system. The cooling fans shall be
mounted on the transformer sides. The cooling systems shall be designed to ensure a maximum
temperature rise of 500C when operating at full load and normal ambient conditions. Contacts
of the winding temperature indicators shall be used to control the starting and stopping of the
fans. The fans shall be operated (on/off) at different temperatures. The necessary valves for
transformer bleeding shall be provided.
1.3 Tap changer
On-load tap changer shall be provided with a handle for manual operation. Tap position shall
be indicated on the tap changing mechanism and in the SCADA system. Completion of tap
changing process/cycle shall be monitored and indicated. The tap changers shall have both local
and remote operation facilities.
1.4 Bushings
Both HV and LV windings shall be brought out separately through bushings in accordance with
IEC 60137. HV bushings must be fitted with protective spark gaps.
The transformer shall have the following bushings: HV, HV neutral and LV bushings.
1.5 Current transformers
The neutral bushing shall be provided with current transformers for Restricted and
Instantaneous Earth fault protection of the transformer.
Each HV phase bushings shall be provided with the current transformers for differential and
over current protection of the transformer. The ratings of the turret CTs shall be suitable for
their protection functions.
The LV bushings shall be provided with the current transformers for winding temperature
indication.
The terminals for the bushing CTs shall be clearly marked and polarity indicated.
1.6 Transformer protection
Transformers shall have Buchholz relay, pressure relief device, oil level indication gauge,
winding temperature and oil temperature mercury thermometers with alarm and trip contacts.
The devices shall be wired to the marshalling kiosk. The above protection signals shall be hard
wired to the protection relay and to the common plc panel.
1.7 Conservator
The transformers shall be provided with a conservator for expansion of the oil which shall be
sized with due regard to the full range of climatic and operating conditions.
A dehydrating breather shall be fitted to each conservator. The conservators shall be fitted with
valves for draining and filling of the conservator.
1.8 Tank
The tank shall be of welded steel construction and shall be designed to withstand all stresses
which may occur in service, during transport and during oil treatment, including full vacuum
with radiators fitted. The transformer tank shall be fitted with valves for draining, filling and
filtration of the oil in the transformer.
1.9 Oil
Transformer oil shall also be supplied to fill the transformers delivered. The oil supplied shall be
mineral oil and shall comply with IEC 60296. 20% more oil shall be supplied in oil drums of
approximately 200 litres.
1.10 Core, winding construction
The core of the transformer shall be constructed of non-ageing cold rolled grain oriented low
carbon silicon steel. The maximum flux density at rated voltage and frequency shall not exceed
1.65 Tesla.
The windings shall be designed to withstand all dielectric, electromagnetic and thermal stresses
which might occur under the operating conditions including those produced by lightning
surges, short circuits, faulty synchronising and vibration. The windings shall also withstand
mechanical shocks originating from handling during transport and seismic disturbances.
1.11 Marshalling kiosk
Marshalling kiosk shall accommodate the following: - winding temperature indicator, oil
temperature indicator, circuit breakers and selector switches for fan control, terminal blocks for
wiring of field device. All the field devices shall be wired to the marshalling kiosk for connection
to the control room for indication, control and alarming purposes. The wiring inside the kiosk
shall be well labelled and laid in the trunkings in good workmanship.
2. AUXILIARY TRANSFORMER
The transformer shall be of the mineral oil immersed core type suitable for outdoor use with Oil
Natural Air Natural (ONAN) cooling.
Transformer supplied shall comply with IEC 60076
2.1 Rating
The transformer shall be rated at 11000V / 415V, Dyn11, 50Hz. The contractor shall determine
the power rating of the station transformer. The transformer rating shall be at least 20% more
than the determined load in the power house and auxiliary loads. The impedance rating of the
transformer shall be guided by the IEC 60076
2.2 Cooling system
The cooling systems shall be Oil Natural Air Natural (ONAN).
2.3 Tap changer
The transformer shall be provided with approved off circuit tap changing equipment.
2.4 Bushings
Both HV and LV windings shall be brought out separately through bushings in accordance with
IEC 60137. Alternatively, the LV bushings may be brought out through a cable box.
The transformer shall have the following bushings: HV, HV neutral and LV bushings. The HV
bushings must have protective spark gaps (arcing horns).
2.5 Insulating Oil
The transformer shall be filled with low viscosity mineral insulating oil, which in every respect
complies with the provision of IEC 60296.
2.6 Protection
Transformer shall have Buchholz relay, pressure relief device, oil level, winding temperature
and oil temperature mercury thermometers with alarm and trip contacts. The protection devices
and such other accessories shall be wired to the marshalling kiosk. The above protection signals
shall be hard wired to the protection relay and to the common plc panel.
2.7 Current Transformers
Current transformers shall be provided for the station transformer protection scheme. The
Current transformers shall comply with the requirements of IEC60044-1. They shall be class
0.5, with a secondary rating of 1A.
3. SWITCHYARD SWITCHGEAR
There shall be a substation whose proposed layout is shown in drawing 2. In the outdoor
substation, there shall be the following:
1. 11kV Isolators
2. 11kV SF6 Circuit Breakers
3. 11kV Overhead Busbar
4. 11/0.415kV Alternative Feeder Transformer
5. 11kV XLPE Power Cables
6. 11kv Surge Arresters
7. Tana 1 & 2 take-off
VERTICAL SWING SINGLE BREAK
3.1 11KV ISOLATORS/DISCONNECTOR SWITCHES
 The isolators supplied shall conform to IEC 62271-102 and other recognized
international standards.
 The disconnector switches /isolators shall be of the vertical swing, single-break type with
porcelain insulators. They shall be 3 phase, non-motorised with a provision for applying
padlocks for safety purposes. All apparatus required for manual operation of the
disconnector switch shall be supplied.
 The operating mechanism shall be extended to a level appropriate for human operation.
 The disconnector switches shall have integral earthing switches with the necessary safety
interlocks.
 The operating mechanism, terminal blocks and cables shall be placed in a weatherproof
kiosk and mounted on the support structure and not directly below the busbars.
 The indications for isolator OPEN or CLOSED shall be wired to the Common PLC for
indication purposes.
 The contractor shall determine the current rating of the isolators suitable for operation
at nominal voltage rating of 11kV.
 The isolator shall be designed for switching of transformer charging current and shall
have necessary interlocks with the circuit breaker to prevent its operation under load
conditions.
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The moving and stationary contacts shall carry the rated load and short circuit currents
without welding and shall be approved by the employer before supply.
The isolators shall be supplied with galvanized steel structures for support. The safety
and working clearance shall be observed during the design of the structures.
3.2 11kV SF6 CIRCUIT BREAKERS
 The breakers supplied shall conform to IEC 62271-100 and related standards.
 The breakers shall be 3 phase breaker with a single operating mechanism. Such
mechanism shall have anti-pumping circuits, operation counter, local/remote selection
switch, breaker position auxiliary contacts and a power socket outlet.
 The breaker shall be capable of carrying the rated and short circuit current without
damage to its contacts or arc quenching mechanism. It shall be capable of switching
magnetizing currents of the transformers, out-of-phase switching and short-line faults
that may occur in service.
 The breaker shall have a motorized spring changing mechanism supplied by 110VDC.
There shall be provision for manual charging of the spring and the required apparatus
shall be supplied with the breakers.
 The breakers shall have auto-reclosure and synchronizing facilities/features and
associate control circuits.
 The breaker control and trip circuits shall be supplied with 110VDC from the station
batteries. Each breaker shall have two trip coils with independent but duplicate trip
circuits. There shall be breaker fail protection on these breakers.
 The breaker shall have facilities to monitor SF6 gas levels and issue alarm and lock-out
breaker operation in case of a low and very low gas levels respectively. There shall be
provision for refilling of the gas.
 There shall be local and remote indication of alarms. The local indications shall include:
Breaker ON/OFF/TRIP status, spring charge/discharge status, breaker Lock out. The
remote indications shall consist of the above alarms including the gas alarm and lock out
events, local/remote selector position. The remote indications shall be wired to the
common PLC.
 The breakers operating mechanism, controls, terminal blocks, local indications and
cables shall be housed in weather-proof, vermin-proof enclosures and shall mounted on
the supporting structure of the breaker, preferably to the side of the busbars.
 The supporting structure shall be made of galvanized steel and shall be designed with
consideration of safety and working clearances.
3.3 11kV OVERHEAD BUSBARS
 The overhead busbar shall connect Tana Feeder 1 to Tana Feeder 2 via a disconnector
switch.
 The disconnector switch shall conform to the specifications above.
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The rating of the overhead busbar shall provide for transfer of power from either
generator transformer to any of the transmission line. This will provide the required
operational flexibility of the two lines.
The busbar shall be supported by well designed galvanized steel structures. Wooden
support structures shall not be allowed.
3.4 11/0.415KV ALTENATIVE FEEDER TRANSFORMER
 The existing 11/0.415kV Station transformer shall be re-located to the outdoor
switchyard.
 The high voltage shall be connected to the 11kV overhead busbar via a disconnector
switch. The overhead conductors and the disconnector switch shall be of a suitable rating.
 The low voltage side shall be connected to the main 415VAC switchboard in the
powerhouse via power cables of a suitable rating.
 The disconnector switch supplied shall comply with the specifications above.
 Appropriate cable termination accessories shall be used to terminate the power cable on
both ends.
3.5 11KV XLPE POWER CABLES
 The XLPE Cables and accessories supplied shall conform to the applicable standards
among them IEC 60183, 60502-2
 The XLPE cables shall be used for the connection of the 11kV terminals of the generators
to the 11kV powerhouse switchboard and from this board to the generator transformer
cable boxes.
 The cables shall be appropriately rated for evacuation of power from the two bus sections.
 Linear Heat Detectors shall be laid on all the XLPE cables used for power evacuation.
These cables shall be laid as per applicable standards.
 The cables shall be neatly laid in cable trenches on cable ladders and trays as is good
engineering workmanship. There shall be segregation of the various cable sizes and
rating.
3.6 SURGE DIVERTERS
 There shall be surge diverters for the protection of the transformers. They shall be
installed on the high voltage side of the transformer.
 The surge arresters shall comply with the requirements of IEC 60099-4.
 They shall be of the metal-oxide type and shall be supplied with porcelain housings. The
surge arresters shall be provided with insulated bases, grading rings, foundation bolts
and supporting structures.
 On each phase, the surge diverters shall have an operation counter and a leakage current
monitor. The leakage current shall be shown by use of a suitable scale. The scale for
leakage current shall have graduations to indicate alarm and trip levels
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The surge arresters shall be fitted with suitable pressure relief devices to prevent the
porcelain shuttering in case of arrester failure.
3.7 TANA 1 & 2 FEEDER TAKE-OFF
 The contractor shall supply, install, test and commission the line breakers, CTs and VTs,
disconnector switches with integral earth, post insulators and associated accessories for
each feeder.
 The contractor shall establish the take-off gantry structure, string and terminate the
conductors on the existing feeders to the 11kV busbar.
 The contractor shall as well establish the lightning arresters and protection for the
substation.
 All substation structure shall be made of hot-dip galvanized steel to prevent rusting of
the said structures.
3.8 Mesco Feeder Take-Off.
 The contractor shall supply, install, test and commission the line breakers, CTs and VTs,
disconnector switches with integral earth, post insulators and associated accessories for
each feeder.
 The contractor shall recover the existing XPLE cables running from the power house to
the overhead line next to the substation. The recovered cables shall be handed over to the
employer
 The contractor shall establish the take-off gantry structure, extend and terminate the
OHL conductors of the Mesco feeder to the 11kV busbar via the switchgear specified
above.
 All substation structure shall be made of hot-dip galvanized steel to prevent rusting of
the said structures.
3.9 REMOTE OPERATION OF SWITCHYARD EQUIPMENT.
There shall be remote operation of the circuit breakers in the switchyard. The remote operation
shall be possible from the DCS and from control cubicles. The control circuits for the transformer
breakers shall be located in a suitable cubicle or in the transformer protection relay cubicles.
The control circuits for the line/feeder breakers may be located in the line protection relay
cubicle.
The On-load tap changers of the transformers shall also be operable as described above.
3.10 Inspections and Tests
Factory Inspections
Circuit breakers, disconnectors, current transformers, voltage transformers, surge arresters,
insulators, conductors, fittings and structures shall be tested in accordance with the
requirements of the relevant IEC standards.
Type certificates will be accepted in lieu of type tests; however where type test
certificates are unavailable the type tests shall be performed.
All equipment will be subject to routine tests in accordance with the relevant IEC
standard.
Tests on Completion
As a minimum, the following site tests shall be performed:
Circuit breakers:
(a) Visual inspection
(b) Insulation resistance
(c) Functional tests
(d) Interlocking test
Disconnectors:
(a) Visual inspection
(b) Insulation resistance
(c) Functional tests
(d) Interlocking test
Current Transformers:
(a) Visual inspection
(b) Insulation resistance
(c) Polarity
(d) Primary injection
(e) Ratio check at actual burden
(f) Measurement of burden
(g) Verification of excitation curve
Voltage Transformers:
(a) Visual inspection
(b) Insulation resistance
(c) Polarity check
(d) Turns ratio
Surge Arresters:
(a) Visual inspection
(b) Surge counter operation test
Transformers
Tests of insulation while in storage at site
The Contractor shall measure, at not more than weekly intervals, the insulation
resistance as specified, or as directed by the Engineer, using a d.c. voltage of 2 kV. The
Contractor shall investigate and take corrective action for any significant drop in resistance
compared to the values recorded at the factory or during storage.
Factory Acceptance Tests
Type tests may be waivered on submission by the Contractor of a certified type test report for
tests carried out by an independent accredited testing agency on transformers of the
same type, voltage and power rating. The certificates shall be provided to the Engineer no
later than 6 weeks before the scheduled factory testing date of the transformer. The decision
to waiver the test shall lie solely with the Engineer.
The transformer and ancillaries shall be subjected to the following tests at the
manufacturer’s factory.
Transformer Material Tests
The following material tests shall be carried out on all important stressed steel
components.
(1) Dimensional checks of all components and assemblies.
(2) Non-destructive Testing of Welds:
(3) Sample tests of core lamination material for magnetic characteristics and losses.
Transformer Hydrostatic Tests
The transformer complete with coolers and fittings and filled with oil shall be tested with an
incremental pressure of 35 kPa for 24 hours and shall be completely free of leakage.
Transformer Bushing Tests
Type tests, sample tests and routine tests in accordance with IEC 60137.
Current Transformer Tests
Type and routine tests in accordance with IEC 60044. For all 11kV current transformers the
dielectric test shall be applied to a test conductor fitted in the current transformers to represent
the busbar.
Tap-Changer Tests
Type and routine tests in accordance with IEC 60214.
Transformer Cooling Equipment, Protection and Alarm Devices Tests
The proper functioning of all thermometers, fan and pump controls and other devices shall be
tested.
Transformer Core Tests
A 2,500 V insulation tester shall be applied between each core bolt and the core
laminations after final tightening of bolts.
Complete Transformer Tests
The transformer shall be subjected to the complete series of type and routine tests in
accordance with IEC 60076, including:
(a) Temperature rise test (first transformer only)
(b) Dielectric type tests
(c) Measurement of winding resistance
(d) Measurement of voltage ratio and phase displacement
(e) Measurement of short circuit impedance and load loss
(f) Measurement of no-load loss and current
(g) Dielectric routine tests
(h) Tests of off-load tap-changer
(i) Partial discharge tests applied as a routine test for the Generator Transformer
(j) Full wave impulse-voltage withstand tests applied as a routine test to the Generator
Transformer.
During the tests of the complete transformer, core loss, excitation voltage and excitation
current shall be measured at 15 minute intervals over a period of 6 hours with the transformer
excited at rated frequency and 110 percent voltage. This test shall be made after the highvoltage withstand tests.
Transformer Special Tests
Special tests in accordance with IEC 60076 shall be carried out including loss tests and
measurement of sound power level.
Generator Transformer loss tests shall be carried out to demonstrate compliance with
Performance Guarantees.
Tests on Completion
Transformer Preliminary Tests at Site
The preliminary tests including tests on transformer auxiliary equipment shall include the
following:
(a) Check impact recorders (where applicable) on installation, and if significant impact is
recorded carry out a comprehensive check for external and internal damage.
(b) Tests of transformer oil for moisture and dry out if necessary.
(c) High-voltage tests at the site test voltages specified in the relevant IEC Standards.
Where site test voltages are not specified in the standards the test levels shall be 75
percent of the factory test values.
(d) Measurement of winding resistance of transformer.
(e) Insulation resistance measurements at the specified voltages appropriate to the circuits and
equipment.
(f) Ratio and polarity check of current transformers and test of magnetizing curve.
(g) Proof of phasing or polarity of power cables.
(h) Proof of control connection and continuity of wiring for all control, protection, auxiliary
and alarm equipment in accordance with the overall diagrams as provided by the
Contractor.
(i) Operation of all control equipment at 80 percent, 100 percent and 110 percent of rated
voltage.
(j) Demonstration of sensitivity of gas and oil surge relays.
(k) Tests of all temperature and level indications, displayed quantities and analogue
outputs to show such items are within the accuracy limits specified.
Transformer Commissioning Tests
The Tests on Completion shall include the following:
(a) Demonstration of performance in service of all auxiliary equipment including tap changer.
(b) Demonstration that all controls, alarms and indications, including displays, operate
correctly.
(c) During the above tests the whole of the equipment shall perform without
adjustment.
(d) Tests to verify that the performance of transformers is in accordance with the Contract,
including monitoring of winding and oil temperature during sustained loading.
(e) The Reliability Test Period.
Applicable Grid Code
The applicable Grid code is available at the following website - www.erc.go.ke/
ANNEX 7: METERING SYSTEM
Technical Specifications
The contractor shall establish new metering systems for the station as described below. The
metering systems shall include:
 Energy meters
 Metering instrument transformers
 Metering accessories
1. Energy meters
The energy meters shall conform fully to the requirements of IEC 60687, IEC 1358 and IEC
60211, for accuracy class 0.2 energy meters and other pertinent specifications.
The meters shall have an auxiliary supply of either 110VDC or 24VDC. This shall ensure the
meters are supplied even in situation of loss of the grid voltage.
1.1. Registers
Meter readings from fiscal energy meters associated with each generator shall be
interfaced via IEC 62056-21 protocol (Electricity metering - Data exchange for meter
reading, tariff and load control - Part 21: Direct local data exchange) and forwarding
the data to the KenGen CDC.
The following registers shall be read and displayed on the SCADA system: Revenue Data
(Active Energy Export, Active Energy Import, Reactive Energy Export, and Reactive
Energy Import), Demand Values (kW, kVA, kVAr and Maximum Demand), Voltage,
Current, Frequency, Power Factor, Load Profile and End of Billing Period Energy Register
Value (Monthly).
The energy register quantities to be displayed on the meter display shall be userprogrammable. The LCD display shall be capable of displaying 14 digits inclusive of digits
after the decimal point.
The meters shall have LED indicators for testing and indication of active energy and
reactive energy metering with one LED dedicated to active and the other to reactive
energy operation. The LEDs shall flash at a rate proportional to active power and reactive
power consumptions respectively.
1.2. Configuration
The energy meters shall be configurable for use in both 3-phase 4 wire and 3-phase 3wire 2 elements networks
The secondary voltage (line voltage) of the voltage transformers shall be userconfigurable between 100—500V. The energy meters shall be capable of operation with
voltages within this minimum ranges.
The energy meter shall be dual-rated for operation with both 1 Amp and 5 Amps and the
choice between the two shall be user-programmable.
Seals
The meters supplied shall have provisions for applying tamper-proof seals. Such seals
may be applied on the face/front covers, on the terminal block covers etc. Application of
seals on the provisions shall ensure that the connections on the meters shall only be made
when the applied seals are broken.
1.3. Memory
The meter shall have a non-volatile memory capable of data storage and with long-term
data retention.
The meters shall be capable of freezing billing readings on any user-selectable date of the
month and make these quantities be displayed on the SCADA system. At least twelve
billing historical data shall be stored in the memory and be retrievable by software action.
1.4. Clock
The meters shall be equipped with a real time clock controlled by a quartz crystal
oscillator. It shall be possible to reset the clock without loss of billing data. The energy
meter shall have an input signal that allows GPS time synchronization.
1.5. Programming software and hardware
The contractor shall provide programming software which shall be windows-based,
ready for use with the latest Windows operating software. The licence for the
programming software shall also be provided. The licences shall be for all the meters and
should enable the programmer to carry out all meter configurations. A similar copy of
the metering software and license shall be provided to Kenya Power for their use.
Two (2) Optical probes complete with a laptop and required accessories for
programming and downloading the meter data shall be provided. The optical probes shall
be provided with an USB at one end to facilitate connection to the programming device
and a magnetic optic head at the other end for hands-free attachment to the meter.
Protection against Penetration of Dust and Water Shall conform to the degree of
protection of IP51 as per IEC 529.
Training shall be carried out by the contractor on KenGen (3 staff) and Kenya Power (2
staff) on meter configuration for a duration of three days. It shall include a class room
set-up and on-site demonstrations.
2. Energy Billing System
There shall be a main metering for use by KenGen for billing purposes and check metering for
use by Kenya Power for back up purposes. The power generated from the station shall be metered
at the switchyard after the generator transformers by use of instrument transformers and energy
billing meters. The metering system installed shall have independent metering circuits for each
meter. Each metering circuit shall have a current transformer core and voltage transformer core
dedicated for the main meter and similarly for the check meter. No other devices shall be
connected to this circuits, whatsoever the situation.
Additionally, one voltmeter (one phase) and ammeter (one phase), one multifunction power
analyser per generator transformer, shall be installed in the switchyard control panel.
3. Metering of Generator Output
The output of the generator shall be metered at the generator phase terminals. The CTs shall be
class 0.5, inductive type with a suitable ratio. The secondary current of the CT shall be 1A. The
VT shall be inductive type with class 0.5 accuracy, voltage ratio 11000/√3/110/√3V, 50Hz.
There shall be energy billing meters for each generator located in the metering panels as
specified above. These meters shall be of accuracy class 0.5 with the other features as specified
above for export/import (clause 2).
Additionally, there shall be
a. Multi Function Power Analysers for each generator located in the unit control panel.
b. Analog indication meters for Current, Voltage, Active Power and Reactive Power for each
generator and located in the unit control panel.
c. Analog indication meters for Current (one phase), Voltage (one phase), Active Power and
Reactive Power for each generator and located in the auxiliary control panel. These
devices shall be connected directly from the CTs and VTs in the 12kV switchboard.
4. Metering of Auxiliary Consumption
There shall be metering of the following auxiliary supplies
 New Station transformer
 Old station transformer
 Diesel Generator
The tariff meters used shall be of the same features as described above. However, they shall be
class 0.5. The auxiliary consumption shall be metered at 415VAC. The CT may be housed in the
main 415VAC switchboard. Alternatively, they may be placed in any other approved position.
The meters shall be mounted in the metering panel described above.
5. Metering of Transmission Lines
There shall be metering circuits for each of the three transmission lines. These circuits shall
include:
a. Line CTs and VTs.
b. Ammeters (one phase) and Voltmeters (one phase).
c. Multifunction power analysers.
Items (b) and (c) above shall be located in the Feeder control panel. The specifications for the
items in (a), (b) and (c) are provided in the clauses below.
6. Metering Panels.
There shall be metering panels for the installation of the billing meters. The panels shall have a
lockable door (key operated lock), a door switch operated fluorescent lighting and with a
minimum sheet thickness of 1.5mm.. They shall be vermin proof, free standing, have bottom
cable entry and glass panel suitable for viewing of the meter display readings. The panels shall
be located in the control room of the power house.
In this panel, every meter circuit shall be installed with test terminal blocks to enable testing of
meters by secondary injection without unscrewing of cables used in metering circuits.
The control cable used shall be of stranded copper conductor, PVC insulated, sheathed with steel
armour, overall PVC sheath and with a minimum cross-sectional area of 2.5sqmm for CT and
VT circuits. Such cables shall confirm to BS 6346.
The cubicles shall be two in number, one for KenGen (colour Orange) and one for Kenya Power
(colour Blue). Permanent labels of an acceptable size shall be affixed on the respective panels.
The labels shall read “KenGen Main Metering” and “Kenya Power Check Metering” respectively.
KenGen Main Metering panel shall have the following tariff meters installed:
a. Main Energy Billing Meters for Generators Transformers 1 and 2
b. Tariff meters for each generator
c. Tariff meter for each station auxiliary consumption
d. Tariff meter for the diesel generator.
Kenya Power Check Metering panel shall have the following tariff meters installed:
a. Energy Billing Check Meters for generator transformers 1 & 2
b. Provision for future installation of two tariff meters for Tana 1 & 2 lines. Such a provision
shall be of adequate capacity.
7. 11kV metering voltage transformer
The voltage transformers (VT) shall be of the outdoor, inductive type and shall comply with IEC
60044-2 and IEC 60186. They shall be of class 0.2 and a voltage ratio of 11000/√3/110/√3V.
The highest voltage for the VTs shall be 12kV as per IEC 60038. The contractor shall determine
the required burden rating of the VTs. On the secondary circuit, there shall be a miniature circuit
breaker for control of the VT output.
The VT shall have a minimum of two cores for metering purposes: One core for KenGen’s main
metering and one core for Kenya Power’s check metering. The primary circuit of the VT shall be
solidly earthed. The VT shall be mounted on galvanised steel structures of a height that ensures
and observes safety clearances. The structures shall be connected to the earthing system of the
switchyard.
The VT may have additional cores for use as the necessary.
8. 11kV metering current transformer
The current transformers (CT) shall comply with the requirements of IEC60044-1. The CTs
shall be of Class 0.2 with a secondary output of 1A, a highest voltage rating of 12kV as per IEC
60038. The contractor shall determine the required ratio and burden rating of the CTs.
The CT shall have a minimum of three cores: first core for main metering, second core for Kenya
Power’s check metering and third core for over-current protection of the line.
The CT shall be outdoor type and shall be mounted on galvanised steel structures of a height that
ensures and observes safety clearances. The structures shall be connected to the earthing system
of the switchyard.
9. Multifunctional Power Analysers
These are digital analysers used to measure, monitor and record power and energy quantities.
These specifications shall be applicable for all analysers supplied under this project.
The analysers shall be capable of indication instantaneous and average power values (kW, kVAr,
kVA, A, V, f, pf etc), instantaneous, cumulative and average energy values, as well as demand
values. The analyser shall be capable of recording both energy import and export and with a
non-volatile memory.
The analyzer shall have an LCD display with minimum four rows for indication. It shall be
possible to configure the analyser by use of function keys provided on the device, albeit via a
password. The analyser shall be 96 X 96mm in size.
The analysers shall be capable of 3-phase 3-wire and 3-phase 4-wire configurations, which
shall be selectable during configuration of the analysers.
The analyser should have a minimum of three 4 -20 mA outputs for Current, Voltage and Active
Power outputs. Such outputs may be connected to the Unit Control Board for indication
10. Power instruments
The power instruments include meters for indication ov voltage, current, power, reactive power
among others. They shall be of 96 X 96mm in size, 900 deflection, with a scale with black
numbering on a white background. The nominal values of the quantities measured shall be
indicated by a red mark. These specifications shall be applicable where such instruments are
specified.
ANNEX 8 - 415V SWITCH BOARD AND AUXILIARIES CONTROL
AUXILIARY SUPPLY TO THE POWER STATION
The station will be supplied by power via
1. Old alternative supply transformer, connected to the overhead 11kV busbar at the yard.
2. New Station transformer, connected on Section 2 of the indoor 11kV switchboard.
3. Emergency Diesel generator.
A single line diagram for the auxiliary supply has been shown as diagram 2.
There shall be an auxiliary supply switchboard rated at 415VAC. The switchboard supplied shall
be in conformance to international standards among them IEC 60158, IEC 60439-1, -2, -3 and
60947(applicable parts). The entire switchboard shall be manufactured in accordance with
known type-test assemblies whose type test results shall be submitted as part of bid documents.
The design and operational philosophy of the switchboards must be submitted for review and
approval by the employer before any assembly or manufacture can begin.
The proposed main switchboard is shown in drawing 3 “Proposed Main Auxiliary Power
Switchboard”. There shall be the following auxiliary switchboards:
1. Main Auxiliary Power Switchboard
2. Motor Control Centre (MCC) 1
3. Motor Control Centre (MCC) 2
4. Station Motor Control Centre (MCC)
1. MAIN AUXILIARY POWER SWITCHBOARD
The proposed switchboard is shown as drawing 3 ”Proposed Main Auxiliary Power
Switchboard” and shall have the following features:
 The switchboard supplied shall be in conformance to international standards among
them IEC 60158, IEC 60439-1, -2, -3 and 60947(applicable parts). The entire
switchboard shall be manufactured in accordance with known type-type assemblies
whose type test results shall be submitted as part of bid documents.
 Two bus-sections (1 & 2) with the new station transformer (Stx 1) on Section 1 and old
alternative feeder transformer (Stx 2) on section 2. There shall be a bus coupler to couple
the two sections. The bus coupler shall always be in OPEN position when in normal
operating conditions.
 The operation philosophy of the three incomers to this switchboard is as follows:
o Station transformer 1 shall have the duty selection where all the loads shall be
supplied from this transformer as long as the switchboard is supplied with power
either from the grid or from generated units.
o In case of loss of supply from the station transformer 1, automatic change over to
the alternative feeder shall occur. Automatic change over from the alternative
feeder to the station transformers shall occur as soon as the supply on the station
transformer has stabilized.
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o In case of loss of both the station transformer one and alternative feeder, the
emergency diesel generator shall start and its circuit breaker closed automatically
to supply the power house loads.
o Automatic change over from the emergency diesel generator to the station
transformer or alternative feeder shall occur as soon as the supply on the station
transformer has stabilized.
The incoming breakers shall be Air Circuit Breakers of appropriate rating. The breakers
shall have over-current settings for appropriate protection of the incoming feeders. The
feeders shall incorporate robust under-voltage relays in their control circuits.
There shall be voltage and current indications for each incomer by use of multifunction
power analysers and analog meters. The features of the power analysers are as specified
in annex 7, clause 8. The ammeter (one phase) and voltmeter (one phase) shall
connected via CTs, VTs or by direct connection. These devices shall be installed in this
switchboard.
Outgoing circuits shall be fitted with air circuit breakers or MCCBs as may be
appropriate. The contractor shall rate the circuits as in good engineering designs. The
outgoing circuits are shown on the single line diagram for this switchboard. The
contractor may add outgoing circuits to this board as per his design.
The control voltage shall be either 110VDC from the station batteries or 24VDC
converted from the station batteries supplies.
There shall be local indications using LED lamps for ON/OFF/TRIP status for the
incoming and outgoing feeders/circuits. The ON/OFF/TRIP status shall also be indicated
in the SCADA screens via the PLC. Additionally, there shall be indications for ISOLATED,
SERVICE, TEST positions with the necessary safety interlocks.
There shall be local/remote/auto selector switches. Remote selection shall allow control
of the circuit from a remote location (SCADA/PLC) while auto selection shall be used for
automatic changeover control (hard-wired) via under-voltage relays of the switchboard.
Power supply to the Drainage Pumps , AC emergency lighting and the Winch shall be
connected to Section 2 of the busbar to ensure that they can be supplied by the emergency
diesel generator incase of total loss of the grid.
The drainage pumps shall be supplied via DOL starters. The winch shall be supplied from
this switchboard according to the specifications of the contractor
rehabilitating/renewing it.
The incomers to the switchboard shall be metered as detailed under the specification for
metering systems.
In addition, there shall be multifunction power analysers and analog panel meters for
voltage and current indication.
2. MCC 1, MCC 2 and STATION MCC
The MCC 1 & 2 shall supply power to the generator equipment and auxiliaries while the station
MCC shall supply power to the non-generator related loads. MCC 1 shall be dedicated for
Mathioya River units and MCC 2 shall be for Maragua River units. The proposed MCCs are
show as drawings 4 “Proposed Unit MCC) and Drawing 5 “Proposed Station MCC”.
The specifications for the MCCs are as follows:
 The switchboard supplied shall be in conformance to international standards among
them IEC 60158, IEC 60439-1, -2, -3 and 60947(applicable parts). The entire
switchboard shall be manufactured in accordance with known type-type assemblies
whose type test results shall be submitted as part of bid documents. The TTA shall be form
3b with withdrawable drives and breakers.
 There shall be two incomers into each MCCs – one incomer from each bus section –
connecting to a common busbar.
 The incomer breakers shall be Air Circuit Breakers of appropriate rating. The breakers
shall have over-current settings for protection of the incoming feeders. The feeders shall
incorporate robust under-voltage relays in their control circuits.
 Outgoing circuits shall be fitted with direct-on-line (DOL) starters for pump supplies
and appropriate circuit breakers for other circuits. Each Pump starter shall incorporate
phase failure relay in the circuit for the protection of the supplied motors. The controls
per circuit shall be totally withdrawable from their cell locations.
 The control voltage shall be either 110VDC from the station batteries or 24VDC
converted from the station batteries supplies.
 There shall be local indications using LED lamps for ON/OFF/TRIP status for the
incoming and outgoing feeders/circuits. The ON/OFF/TRIP status shall also be indicated
in the SCADA screens via the Unit PLCs for MCC1 & 2 and via Common PLC for Station
MCC. Additionally, there shall be local indications for ISOLATED, IN SERVICE positions
with the necessary safety interlocks.
 There shall be local/remote/auto selector switches. Remote selection shall allow control
of the circuit from a remote location (SCADA/PLC) while auto selection may be used for
pump control by switches or applicable instruments.
 The number of outgoing circuits shall be determined by the contractor’s proposed
circuits/loads. Two spare cells shall be supplied complete with a DOL starter of a similar
rating to the highest load in each MCC. Additionally, there shall be two empty spares
cells for future use by the employer. The empty cells shall be supplied ready for fitting
with starters/controllers by the employer.
 There shall be local indication of current and voltage on each incoming and outgoing
circuit by use of analogue gauges of appropriate size.
Factory Acceptance Tests
Routine and type tests shall be carried out on the switchboards, circuit breakers,
contactors, current and voltage transformers, and protection relays in accordance
with the applicable IEC standards:
Switchboards
Circuit breakers
- Routine tests
- Type tests on one of each type
- Routine tests
Contactors and control gear - Routine tests
Current transformers
IEC 60947
IEC 60056
IEC 60439
IEC 60947
- Routine, type and impulse tests
IEC 60185
Potential transformers
- Routine, type and impulse tests
IEC 60186
Protection relays
- Routine tests
IEC 60255
Factory acceptance tests shall be witnessed by the Client.
Tests on Completion
The 415 V switchboards and switchgear shall be subject to inspection testing and
commissioning. The Contractor shall provide all test sets and test apparatus required for
carrying out the tests. The following site tests shall be performed:
(a) Visual inspection
(b) Insulation resistance tests
(c) Continuity tests
(d) Routine high voltage tests
(e) Protection relay primary and secondary injection tests
(f) Function tests to verify tripping, closing, interlocking, alarms and indications, etc.
DC equipment
Factory Acceptance Tests
The battery chargers, d.c. distribution boards and their components shall be tested in
accordance with the applicable IEC Standards or equivalent.
The works tests shall include, but not be limited to:
(a) Temperature rise;
(b) Insulation resistance;
(c) Operational tests;
(d) Radio interference tests;
(e) Ripple measurement of the charger output without battery connected.
Tests on completion
The following tests on completion shall be carried out as a minimum:
(a) Visual inspection;
(b) Insulation resistance;
(c) Functional tests;
(d) Setting and functional tests of protective devices;
(e) Tests to confirm the charger’s rating;
(f) Ripple measurement of the charger output with battery connected.