Water and Wastewater Power Solution Handbook

Water and Wastewater Power Solution Handbook
Water and Wastewater
Power Solution Handbook
Electrical Distribution
4
Connection to the Utility network
MV circuit configuration
Configuration of LV circuits
Back-up generators
Presence of Uninterruptible Power Supply (UPS)
Monitoring and Measurement
4
5
7
9
10
11
Motor control
12
High power motor supply
Characteristics of different control systems
Motor protection functions
Motor monitoring
Control and protection statistics
Control and protection specific to Variable
Speed Drives
Recommended solutions for control and monitoring
Selection of equipment
Solutions for Conventional control schemes
Solutions for Advanced control schemes
Solutions for High Performance control schemes
Motor Control Center
14
15
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20
21
21
Energy Efficiency
23
Introduction
Implementation of Energy Efficiency
Possibilities for optimization
Intelligent equipment based architecture
"e-Support" becomes accessible
Transparent Ready TM
Solutions for energy savings
Solutions for energy cost optimization
Solutions for Availability & Reliability
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29
Preferred architectures
30
Introduction
Remote lifting and pumping stations P1
Pumping and small booster station P2
Booster and complex pumping stations P3
Autonomous water treatment plant T1
Drinking water treatment plant T2
Wastewater treatment plant T2
Drinking water treatment plant T3
Wastewater treatment plant T3
Drinking water treatment plant T4
Wastewater treatment plant T4
Desalination plant T3
30
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40
Annexes
41
Definition of Water and Wastewater functions
Energy and Power for pumping applications
Typical number of process units and different
functions included
Electrical installation characteristics
List of motor protection functions and result
of activation
Selection of LV switchboards
41
41
42
44
46
47
Electrical Power in Water
& Wastewater Applications
Introduction
At Water facilities, Energy can range from 30 to 50 percent of total operating
costs. This shows the importance of a careful installation design and a strict
energy management on a day-to-day basis.
Installation design can be of critical importance for different aspects,
particularly in reduction of power losses, equipment cost and energy cost.
Energy management can be improved for example by implementation of
measurement and monitoring equipment, resulting in peak shaving and a
better continuity of supply.
Schneider Electric is deeply involved in the Water industry, providing solutions
for both Automation and Power (Electrical Distribution and Motor Control).
The objectives of this document is to provide guidance for architecture and
equipment selection, concerning Electrical Distribution and Motor Control.
The proposed approach is based on a classification of water & wastewater
treatment plants, a review of the relevant characteristics of water industry
plants, and consideration of Energy Efficiency criteria.
Examples of solutions ("preferred architectures") are given, including single-line
diagram and equipment selection.
A similar approach has been developed by Schneider Electric concerning
automation solutions. Please refer to the dedicated documents.
1
Classification of Water industry plants
Classification is based on destination and size
of plants.
Process
Average energy
for 1 m3
Average power
for 1 m3 / day
5 Wh / meter of elevation
0.2 W / m
Drinking water
or Wastewater
treatment
0.5 kWh
20 W
Desalination
(reverse osmosis)
4.5 kWh
185 W
Different types of plants are considered:
> water pumping remote stations,
> drinking water treatment plants, including
desalination plants,
> wastewater treatment plants.
Water and wastewater plants are classified per
the number of m3 of water treated per day or
per the corresponding number of inhabitants.
For each type of water plant, the following table
gives the order of magnitude of the electrical
energy necessary for the treatment of 1 m3, as
well as the corresponding installed power for
treatment of 1 m3 per day.
See in annex the basic calculation of Energy
and Power for pumping applications.
Water supply
The "power demand" (in kVA or MVA), which
represents the maximum power possibly
consumed at a given time by the entire
installation can be derived from the average
power. Different factors must be taken into
account, such as power factor (in the order of
0.9), daily or yearly process fluctuations, …
In the following tables, it is assumed that
the power demand is approximately equal to
1.25 times the average power.
The determination of the installed power of
supply transformers will be based on the Power
demand, the need of redundancy and the
consideration of future extension of the plant.
Water pumping remote stations
Three different types of plants have been
distinguished, depending on destination and size:
> P1: small lifting, pumping and tank station,
> P2: pumping and small booster station,
> P3: booster or complex pumping station.
Number of pumps
Power demand (kVA)
2
P1
P2
P3
2
4
5 – 10
< 500
100 – 1000
500 – 5000
Water treatment plants
For both drinking water and wastewater
treatment, 4 different sizes of plants have been
distinguished. The size of plants can be
expressed in quantity of treated water per day,
or in corresponding number of inhabitants.
See definition of process functions in annex.
Four different types of plants have been
distinguished, depending on destination and
size:
> T1: autonomous water treatment plant,
> T2: small water or wastewater treatment plant,
> T3: medium sized water or wastewater
treatment plant,
> T4: large water or wastewater treatment plant.
T1
T2
T3
T4
1000 – 5000
5000 – 50 000
50 000 – 200 000
200 000 – 1 000 000
Inhabitants
1000 – 10 000
10 000 – 100 000
100 000 – 500 000
500 000 – 1 000 000
Power demand
25 – 125 kVA
125 – 1250 kVA
1.25 – 5 MVA
5 – 25 MVA
T2
T3
T4
5000 – 50 000
50 000 – 200 000
200 000 – 1 000 000
1 – 10 MVA
10 – 50 MVA
50 – 250 MVA
m3/day
(drinking water
or waste water)
The Power demand for desalination by
reverse osmosis technology is higher than for
conventional drinking water plants. As plant
capacity is generally higher than 5000 m3/day,
only sizes T2 to T4 are relevant.
m3/day
Power demand
3
Electrical Distribution
Guidance is given for the selection of
Electrical Distribution architecture.
This includes the selection between different
possible configurations of MV and LV circuits,
the implementation of back-up power sources,
and the selection of equipment technology.
The most relevant characteristics of the
electrical installation are taken into account,
such as typology, power demand, sensitivity
to power interruptions, …
Connection to the Utility network
The most commonly used configurations for
connection are as follows, in the order of
increasing power demand and service reliability:
> LV or MV single-line service,
> MV ring-main service,
> MV duplicate supply service,
> MV duplicate supply service with double
busbar.
MV
LV
MLVS
Single-line
For each connection, one single transformer
is shown for simplification purposes, but in
practice, several transformers can be
connected.
MV
MV
LV
LV
MLVS
MLVS
Ring-main
(MLVS: Main Low Voltage Switchboard)
4
Metering, protection and disconnection
devices, located in the delivery substations are
not represented on the following diagrams.
They are often specific to each Utility company
and do not have an influence on the choice of
installation architecture.
Duplicate supply
MV
MV
LV
LV
MLVS 1
MLVS 2
Double busbar
with duplicate supply
For the different possible configurations, the
most probable and usual set of characteristics
is given in the following table:
Configuration
LV
MV
MV
MV
MV
Single line
Ring main
Duplicate
supply
Duplicate
supply with
double busbar
Autonomous
water treatment
plant T1
Water
treatment plant
T2
Water
treatment plant
T3
Water
treatment plant
T4
Remote pumping
station P1, P2
Remote pumping
station P3
Desalination
T2
Desalination
T3
Desalination
T4
Service reliability Minimum
Minimum
Standard
Standard
Enhanced
Power demand
< 1250 kVA
1.25 – 5 MVA
5 – 25 MVA
> 25 MVA
Characteristic
to consider
Site typology
< 250 kVA
The connection configurations may differ from
the above table due to particular constraints
relative to water industry plants:
> spread-out configuration,
> suburban location.
MV circuit configuration
The main possible connection configurations
are as follows:
> single feeder, one or several transformers,
> open ring, one MV substation,
> open ring, 2 MV substations.
The basic configuration is a radial single-feeder
architecture, with one single transformer.
In the case of using several transformers, an
open ring is commonly realized for improved
power availability.
5
Electrical Distribution
a) Single feeder
b) Open ring, 1 MV substation
c) Open ring, 2 MV substations
MV
MV
MV
MV
MV
MV
MV
MV
LV
LV
LV
LV
LV
LV
LV
LV
MLVS 1
MLVS n
MLVS 1
MLVS 2
MLVS n
MLVS 1
MLVS 2
MLVS n
High power motors may be directly supplied
at MV for reduction of cable size.
The preferred basic configuration comprises
one single substation. However, a larger
number of substations is possible in some
circumstances:
> A large site,
> A site with several different process lines,
> A total power higher than 5 MVA,
> A need for redundancy, to cope with a natural
disaster for example.
The preferred configuration of MV/LV
transformers comprises a single transformer
supplying the total power of the installed loads.
Certain factors contribute to increase the
number of transformers (> 1), preferably of
equal power:
> A high total installed power (> 1250 kVA):
practical limit of unit power (standardization,
ease of replacement, space requirement,
etc…),
> A large site. The setting up of several
transformers as close as possible to
the distributed loads allows the length of LV
connections to be reduced,
> A need for partial redundancy (down-graded
operation possible in the case of a transformer
failure) or total redundancy (normal operation
ensured in the case of a transformer failure),
> Separating of sensitive and disturbing loads
(e.g.: IT equipment, motors),
> Different independent process lines,
> Supply of MV motors,
> Installation scalability (different identical
process lines).
6
For the different possible configurations, the
most probable and usual set of characteristics
is given in the following table:
Configuration
Single feeder
1 substation
1 transformer
Single feeder
1 substation
N transformers
Open ring
1 or 2 substations
N transformers
(different power)
Plant typology
Small
T2
Medium
T3
Large
T4
Power demand
< 1250 kVA
1.25 – 5 MVA
> 5 MVA
Load distribution
Uniform
Intermediate
Localized high
power loads
Maintainability
Minimum
Standard
Enhanced
Disturbance
sensitivity
Long interruptions
acceptable
Short interruption
acceptable
Short interruption
acceptable
Characteristic
to consider
Configuration of LV circuits
Here are the main possible configurations, to be
selected according to the requested level of
power availability:
Radial single feeder configuration
This is the reference configuration and the most
simple. A load is connected to only one single
source. This configuration provides a minimum
level of availability, since there is no redundancy
in case of power source failure.
Two-pole configuration
The power supply is provided by 2
transformers, connected to the same MV line.
When the transformers are close, they are
generally connected in parallel to the same
Main Low Voltage Switchboard (MLVS).
Sheddable switchboard (simple
disconnectable attachment)
Sheddable circuits can be connected to a
dedicated switchboard. The connection to the
MLVS is interrupted when needed (overload,
generator operation, etc…)
Interconnected switchboards
If transformers are physically not too far from
one another, they may be connected by a
busbar trunking. A critical load can be supplied
by one or other of the transformers. The
availability of power is therefore improved, since
the load can always be supplied in the case of
failure of one of the sources.
The redundancy can be:
> Total: each transformer being capable of
Variant: two-pole with two ½ MLVS
supplying the whole installation,
In order to increase the availability in case of
failure of the busbars or authorize maintenance
on one of the transformers, it is possible to split
the MLVS into 2 parts, with a normally open link
(NO). This configuration generally requires an
Automatic Transfer Switch, (ATS).
> Partial: each transformer only being able to
supply part of the installation. In this case, part
of the load must be disconnected (loadshedding) in the case of one of the transformers
failing.
7
Electrical Distribution
Double-ended power supply
This configuration is implemented in cases
where maximum availability is required.
The principle involves having 2 independent
power sources, e.g.:
> 2 transformers supplied by different MV lines,
> 1 transformer and 1 generator,
> 1 transformer and 1 UPS.
Two-pole configuration
MLVS
An automatic transfer switch (ATS) is used to
avoid the sources being parallel connected.
This configuration allows preventive and
curative maintenance to be carried out on all
of the electrical distribution system upstream
without interrupting the power supply.
Configuration combinations
An installation can be made up of several
sub-assemblies with different configurations,
according to requirements for the availability of
the different types of load. E.g.: generator unit
and UPS, choice by sectors (some sectors
supplied by cables and others by busbar
trunking).
Radial single feeder configuration
Two-pole configuration
with two ½ MLVS and NO link
MLVS
NO
MLVS
Shedable switchboard
MLVS
LV switchboard
8
Interconnected switchboards
Double-ended configuration
with automatic transfer switch
or
MLVS
G
or
UPS
MLVS
Busbar
Back-up generators
The electrical power supplied by a back-up
generator is produced by an alternator, driven
by a thermal engine. No power can be
produced until the generator has reached its
rated speed. This type of device is therefore not
suitable for an uninterrupted power supply.
The generator can function permanently or
intermittently. Its back-up time depends on the
quantity of available fuel.
Generators are generally not connected at MV,
except in particular situations:
> Process with co-generation, local bio-gas
production, for optimization of the energy bill,
> When the availability of the public distribution
network is low.
A LV back-up generator operates generally
disconnected from the network. A source
switching system is therefore necessary.
According to the generator’s capacity to supply
power to all or only part of the installation, there
is either total or partial redundancy.
The implementation of a back-up generator
should take consideration of the sensitivity of
circuits to power interruptions and the
availability of the public distribution network.
G
LV switchboard
9
Electrical Distribution
Presence of Uninterruptible Power Supply (UPS)
The electrical power from a UPS is supplied
from batteries. This system eliminates any
power failure. The back-up time of the system
is limited: from several minutes to several hours.
The simultaneous presence of a back-up
generator and a UPS unit is used for
permanently supply loads for which no failure is
acceptable. The back-up time of the batteries
must be compatible with the maximum time
for the generator to start up and be brought
on-line.
A UPS unit is also used for supplying
power to loads that are sensitive to
disturbances (generating a “clean” voltage that
is independent of the network).
Example of configuration for uninterruptible
supply of critical circuit:
G
LV switchboard
Normal
Non-critical
circuit
Main characteristics to be considered for
implementing a UPS:
> Sensitivity of loads to power interruptions,
> Sensitivity of loads to disturbances.
UPS
The presence of a UPS unit is essential if and
only if no power failure is acceptable.
Generally, process lines in Water applications
are not supplied by UPS because of the large
power involved and the possibility to accept
short interruptions.
UPS are necessary only for process control
supply.
10
Critical
circuit
By-pass
Monitoring and Measurement
Objective
Data analysis
Power monitoring and measurement system
dedicated to Electrical Distribution may be of
high benefit for the owner of an electrical
network as a strategic piece in the global
“Energy Efficiency” approach. Fewer expensive
power outages, less energy waste, no
unnecessary maintenance operations: these are
the objectives of a management system based
on Power Quality and Energy Efficiency.
The collected data can be used for improving
Energy Efficiency and Quality of process.
In particular, the setting up of a global
information system in the plant will allow
comprehensive electrical performance data to
be streamed, in real time and remotely for:
> Predicting electrical network non-availability,
> Recording electrical quality,
> Organizing electrical equipment maintenance,
> Better purchasing of electrical energy and in
certain cases, better resale,
> Optimizing consumption per sector, unit, site,
avoiding excessive consumption or abnormal
variations.
Therefore, all of the data required to make
direct savings on electricity billing will be
provided. End users can therefore take
advantage of electrical network monitoring to
avoid any waste and to supply energy where it
is really necessary.
The most relevant parameters for
Electrical Distribution monitoring
Data
Main purpose
Voltage and current:
present, average, minimum,
maximum values
Check stability of supply
Distortion
Reduce line current and power losses
Unbalance
Reduce power losses
Fluctuations
Improve quality of process
Power and energy load profile Detect excessive power consumption
Workshop metering
Reveal major consumers
Active and Reactive energy
Set up improvements
Power factor
Reduce line current and power losses
Solutions
Measurement devices proposed by
Schneider Electric:
> Protection relays: Sepam, TeSys T
> Circuit breaker control units: Micrologic
> Power monitoring devices: PM, CM, ION.
Data made accessible by web server using
Transparent Ready TM equipment.
Measurement data:
> Supply voltage: line-to-line, line-to-neutral,
> Power frequency,
> Voltage unbalance,
> Harmonic distortion: voltage (THDU ), u3 to
u21 (%), current (THDi ),
> Last alarms and trips,
> Power: active (kW), reactive (kvar), apparent
(kVA),
> Power factor (cosϕ, true power factor),
> Energy: real (kWh), reactive (kvarh), apparent
(kVAh),
> Energy: positive, negative.
11
Motor control
Here is presented an overview of motor usage
in water industry. The main control and
protection possibilities are presented, function
of the characteristics of the driven machines.
A selection of adapted Schneider Electric
equipment is proposed.
In water and wastewater treatment plants,
motors are used to drive different kinds of
machines:
> Pumps,
> Moving devices (scrapers, sludge removal, …),
> Mixers (for water or sludge),
> Sludge processing machines (endless screw,
centrifuge, press, conveyor),
> Air blowers (aeration for biological treatment).
Type
Description
Main feature
Centrifugal pump
> A type of pump commonly used in water applications.
> Torque is a quadratic function in
The rotary motion of a profiled impeller in combination
with a shaped pump housing or volute applies
centrifugal force to discharge water from the pump.
> Centrifugal pumps cover a wide range of
volume/pressure conditions.
> The flow from centrifugal pumps can be controlled
easily using valves on the pump discharge manifold or
by changing the speed of rotation.
> Multi-stage pumps are designed for high pressure
membrane feed in reverse osmosis desalination plants.
Dosing pump
> A low-volume fluid pump with controllable discharge
rate used to inject chemical additives to the mixing or
pumping system.
> Dosing pumps are frequently used to inject fluids that
may be difficult to mix efficiently in batch-tank systems
because of their low volume.
Screw pump
relation to speed.
> Large range of power
(1 kW to >1MW).
> A controlled slow-down is highly
recommended for avoiding water
hammer in upstream pipes.
> High starting torque.
> Low power (< 10 kW).
> Also known as Archimedes' screw.
> Used for lifting of large volume of water or sludge on a
> Low fixed rotation speed.
> Driven through a speed reduction
limited height.
gear.
> Axis of the screw is inclined at about 45°.
Mixer
Motion
> Used to give homogeneity to fluids.
> Agitation is also used for speeding-up chemical
process.
> Fixed speed.
> Medium range power (1 to 50 kW).
> The propeller is driven with a speed
> Mixing is performed by a propeller rotating in the fluid.
reduction gear.
> Driving of various types of mechanical systems:
> Constant torque.
> Low power (1 to 10 kW).
screening grills, valves, …
Sludge processing
> A large diversity of machines is observed: conveyor
belts, grinders, sweeping arms, filter press, centrifuge,
scrapers, …
Air blower
compressor
12
> Constant torque.
> Medium range power (1 to 50 kW).
> Provide oxygen for aeration of biological treatment
> High power (100 kW for
tanks.
> Centrifugal or positive displacement blower.
10 000 m3/day of treated water).
13
Motor control
High power motor supply
For high power motors, supply is possible at
MV or at LV. It is assumed that:
> MV supply is possible for P ≥ 100 kW,
> LV supply is possible for P ≤1500 kW.
Both MV and LV are possible between 100 and
1500 kW.
At LV, both 400 V or 690 V are possible.
The main driver for selecting the highest
possible line voltage is the reduction of the line
currents and the resulting power losses.
Other criteria should be taken into account,
such as:
> Proportion of large motors in the installed
power. Example: if only a few high power
motors are present, it may be advantageous to
have all motors supplied at LV, in order to avoid
specific distribution lines at MV.
> Load distribution. Example: if high power
motors are distributed all over the plant area
with long cable distances, the use of MV may
be advantageous in order to reduce power
losses and avoid the use of transformers.
> Availability of skilled personnel.
The resulting solution is obtained by
considering the availability of equipment at
different voltage ratings, and the total cost of
the solution, including: cost of equipment,
cost of cables, installation cost, etc…
Typical voltage allocation:
Voltage
MV
LV - 690V
LV - 400V
100
14
1000
Power (kW)
Characteristics of different control systems
Is / In
Ts / Tn
Speed
control
Torque
control
Direct on-line
5 – 10
2–3
No
No
Star – delta
2–3
1–2
No
No
Auto – transformer
2–3
1–2
No
No
Soft starter
3–5
1.5 – 2.5
No
Yes
1.5
1.5 – 2
Yes
Yes
Variable speed drive
Major benefit
Disadvantage
Direct on-line
Reduced cost
High starting torque
High in-rush current
Star – delta
Reduced in-rush current
Reduced starting torque
Auto-transformer
Reduced in-rush current
High weight
Soft starter
Reduced in-rush current
Controlled start and stop
Reduced starting torque
Variable speed drive
Controlled speed
Energy saving at reduced speed
Higher cost
Is : starting current
In : nominal current
Ts : starting torque
Tn : nominal torque
Variable Speed Drives and Soft Starters can be
used in complex configurations where only one
piece of equipment is able to manage several
motors.
For Soft Starters, a typical arrangement consists
in cascading start-ups and decelerations, with
one controller associated to a set of contactors,
as shown on the following diagram. One motor
soft start or stop is performed at a time, the
other motors being stopped, or running at full
speed directly connected to the mains.
Where several pumps are running in parallel
(multi-pump configuration), the total water flow
can be regulated using one single variable speed
controller supplying one motor, in a scheme
similar as presented above. Only one motor is
running at variable speed, the other motors being
stopped or running at full speed. The multiplexing
function is provided by a dedicated control card.
15
Motor control
Motor protection functions
These are the arrangements implemented in
order to avoid operation of motors in abnormal
conditions which could result in negative events
such as: overheating, premature ageing,
destruction of electrical windings, damage to
coupling or gear box, …
Below is a list of commonly used protection
functions. Three levels of protection scheme are
proposed: "Conventional", "Advanced",
"High Performance", which can be adopted
depending on the sophistication and power
of the driven machine.
Conventional protection functions apply for
every type of motor or application.
High performance protection functions are
justified for high power motors or high
demanding applications.
Protection
Conventional
Advanced
High
performance
Short-circuit
Thermal overload
Current phase imbalance
Current phase loss
Over-current
Earth fault
Long start
Jam (locked rotor during run)
Under-current
Current phase reversal
Motor temperature (by sensors)
Rapid cycle lockout
Load shedding
Phase voltage imbalance
Phase voltage loss
Phase voltage reversal
Under-voltage
Over-voltage
16
Motor monitoring
The objective of implementing measurement
devices is to ensure a continuous supervision of
operating conditions of motors. The collected
data can be used with great benefit for
improving Energy Efficiency, extending lifetime
of motors, or for programming maintenance
operations.
Measurement
Three levels of sophistication for monitoring
scheme are proposed: "Conventional",
"Advanced", "High Performance", which can be
made accessible, depending on the
sophistication and power of the driven machine.
Conventional
Advanced
High
performance
Currents
Average current
Phase current imbalance
Heat capacity level
Motor temperature (by sensors)
Phase to phase voltage
Phase voltage imbalance
Active power
Reactive power
Power factor
Active energy
Reactive energy
Control and protection statistics
Information can be provided by "High
Performance" equipment about history of motor
and controller. The main objective is to facilitate
fault analysis and maintenance programming.
Supervision of motor:
Example of valuable information:
> Operating time,
> Number of starts,
> Number of starts per hour,
> Protection fault counts,
> Protection warning counts,
> Fault history.
Supervision of motor controller:
Example of valuable information:
> Controller internal temperature,
> Check of temperature sensor connections,
> Check of current connections,
> Check of voltage connections,
> Communication loss.
17
Motor control
Control and protection specific to Variable Speed Drives
These features, specific to the variable-speed
operation of motors, can be helpful in the fine
tuning of the process or driven machine.
Protection functions
> Over-voltage due to fast deceleration,
> Overload due to continued operation at lowspeed.
Control information
> Speed reference,
> Actual speed,
> Direction of rotation,
> State of current or torque limitation.
Recommended solutions for control and monitoring
For different types of driven machines, the following table summarizes the main features relative to
different types of driven machines:
Torque
Reversing
Starting time
Risk of jam
Main concern
Recommended
control system
Centrifug.
pump
Dosing
pump
Mixer screw
pump
Motion
Sludge
processing
Air flow
Variable
(Quadratic)
Constant
Constant
Constant
Constant
Variable
(Quadratic)
No
No
No
Yes
No
No
Slow
Fast
Slow
Fast
Slow
Slow
No
Yes
Yes
Yes
Yes
No
Energy
savings
High torque
High in-rush
current
High torque
High in-rush
current
Energy
savings
Soft starter
or VSD
Direct
on line
Soft starter
Direct
on line
Soft starter
Soft starter
or VSD
Conventional
Advanced
Conventional
Advanced
High
performance
Recommended protection
High
and measurement scheme performance
Selection of equipment
Schneider Electric has a complete offer of motor control equipment which is particularly well
adapted to water applications:
> Motor controller: TeSys U, D, F
> Motor Management System: TeSys T
> Soft starter: Altistart 48
> Variable speed drives: Altivar 21, 61, 71
> Intelligent Motor Control Center: MotorSys, with Okken, Prisma Plus or Blokset technology
> MV motor starter: Motorpact RVSS.
18
Solutions for Conventional control schemes
Universal cabinet
1, 2 or 3 product configurations:
> TeSys U starter
> GV3L circuit-breaker + TeSys D contactor
> Compact NSX circuit-breaker + TeSys F contactor + LR9F thermal relay
LVS
19
Motor control
Solutions for
Advanced control schemes
Prisma Plus switchboard
Possible control configurations:
> TeSys U controller
> Compact NSX circuit-breaker + TeSys F contactor + LUTM controller
> Compact NSX circuit-breaker + TeSys F contactor + Altistart 48 soft starter
LVS
20
Solutions for
High Performance control schemes
Motor
Control Center
Okken switchboard
Compared to a traditional switchboard
technology (universal switchboard), a Motor
Control Center (MCC) offers significant
advantages, particularly for a large set of
motors:
Possible control configurations:
> Compact NSX circuit-breaker + TeSys F contactor + TeSys T controller
> GV3L circuit-breaker + TeSys D contactor
+ Altivar 61 Variable Speed Drive.
> Reduced space requirement, allowing more
motor feeders for the same volume,
> Reduced installation times and maintenance
costs,
> Very easy adding of a new feeder or
modifying existing feeders when energized,
> Availability of type-tested equipment,
according to IEC60439-1: “Low-voltage
switchgear and control-gear assemblies; part 1:
type-tested and partially type-tested
assemblies”.
LVS
The particularity of Intelligent Motor Control
Centers (iMCC) is the inclusion of motor
protection equipment, connected via a field bus
to a supervisory system. The latest generation
of iMCC provides compatibility with most of the
communication networks present on the
market.
The resulting advantages are the following:
> Prevention of motor malfunctions,
> Data feedback for continuous improvement in
process control,
> Configuration tailored to suit the criticality of
the process,
> Enhanced process availability and
productivity.
Field experience has shown a significantly
improved efficiency:
> Minimum 70% reduction in unexpected
process downtimes,
> 90% elimination of motor burnouts,
> Over 50% reduction in maintenance costs.
21
Motor control
Concerning protection and monitoring, three
different levels are proposed. The different
possibilities are summarized on this table:
Protection and Monitoring
Prisma Plus
Okken or Blokset
TeSys T + Ext. Module (option)
High
performance
TeSys T
MotorSys Multifunction
TeSys U Multifunction (option)
TeSys U Multifunction (option)
Advanced
MotorSys Advanced
TeSys U Advanced
TeSys U Standard (option)
MotorSys Classic
Conventional
TeSys D
Concerning the water applications, the preferred selection is presented here:
Water industry plant
Switchboard
Protection system
P1, P2, T1, T2
Universal
TeSys U
P3, T3
Prima Plus Blokset
TeSys U
MotorSys Advanced
T4
Okken Blokset
TeSys T
MotorSys Multifunction
22
iMCC
Energy Efficiency
Introduction
As electricity is a key factor in water
applications, both in terms of cost and crucial
source of energy, a special attention should be
given to Energy Efficiency. All its 3 aspects will
be considered here, applied to the Water
segment:
> Energy Savings: reduction of consumption in
> Availability & Reliability: minimize risk of
outage through design and strategy, and
sustain energy gains through reliable and
efficient equipment operation.
It will be explained how a judicious selection of
equipment contributes to Energy Efficiency.
all kinds of operations,
> Energy Cost optimization: reduction of the
cost of energy utilized by different operations,
Implementation of Energy Efficiency
The process can be split into three successive
steps:
Step 1 : formulate priorities
Each water application site has its own
requirements and a specific electrical
distribution architecture. According to the site’s
requirements, the appropriate energy efficiency
applications are determined.
Objective
Application
Consumption
optimization
Cost allocation
Energy usage analysis
Implementation of Variable speed pumps & fans
Lighting control
Energy purchasing
optimization
Peak demand reduction
Power Factor Correction
Electricity procurement optimization
Sub-billing
Improving the
Electrical Distribution alarming
efficiency of teams
and event logging
in charge of electrical
installation operation
Improving energy
Electrical Distribution network remote control
availability and quality Electrical Distribution network automation
Asset optimization
Step 2 : define key electrical values
Once the priorities have been formulated,
the key electrical values to be included in the
measurement system can be defined,
The parameters to take into account must allow
the detection of disturbances or phenomena as
soon as they appear. In other words: before it
has a detrimental effect to the electrical
installation and its current consumers,
Statistical analysis of equipment usage
Harmonic management
to be as close as possible to applications, and
other devices at the site installation head, to
have an overview. It is also needed to identify
vital feeders for the plant operation and feeders
on costly processes.
Example: different types of metering systems
will be implemented, whether the application
consumes a lot of electricity with no high quality
requirements, or if the application is highly
sensitive to Power Quality.
The method includes installing appropriate
monitoring devices on each concerned feeder,
23
Energy Efficiency
Step 3 : select components
For existing installations: some of the electrical
equipment already includes measurement
devices.
Example: protection relays often include
measurement functions. It is only necessary to
make them communicate via a field bus link to
the intranet site.
Here are some examples of the main usage of
the simplest monitoring systems:
> Benchmark between zones to detect
abnormal consumption,
> Track unexpected consumption,
> Benchmark between different sites to detect
discrepancies,
> Select the right delivery contract with the
Power Utility,
> Set-up simple load-shedding, just focusing on
optimizing manageable loads such as HVAC,
> Be in a position to ask for damage
compensation due to non-quality delivery from
the Power Utility. E.g.: The process has been
stopped because of a voltage sag on the
network.
Possibilities for optimization
Optimizing the assets
One increasing fact is that electrical networks
evolve more and more and a recurrent question
is asked : will the network sustain a new
evolution?
This is typically where a monitoring system can
help the network manager or owner in making
the right decision. By its logging activity, the
system can archive the real use of the assets
and the spare capacity of the network,
transformer, or switchboard … can be
evaluated quite accurately.
Monitoring systems can provide accurate
information on the exact use of an asset and
maintenance can be decided at the right time:
not too late, or not too early. A better use of an
asset can increase its life duration.
Increasing the productivity by reducing
the downtime
Downtime is the nightmare of people in charge
of an electrical network. It may cause dramatic
loss for the company, and the pressure for
powering up again in the minimum time is very
high.
A monitoring and control system can help
reducing the downtime very efficiently. Without
considering a remote control system which is
the most sophisticated system and which may
24
be necessary for the most demanding
applications, a simple monitoring system can
already provide relevant information that will
highly contribute in reducing the downtime:
> Making the operator spontaneously informed,
even remotely, possibly out of the concerned
site (using mobile communication such as
Digital Enhanced Cordless Telecommunications
(DECT) network or GSM/SMS),
> Providing a global view of the whole network
status,
> Helping the identification of the faulty zone,
> Having remotely the detailed information
attached to each event caught by the field
devices (tripping cause for example).
Remote control devices are the best solutions,
but not necessarily mandatory. In many cases,
a visit of the faulty zone is necessary where
local actions are possible.
Increasing the productivity
Some loads can be very sensitive to electricity
quality, and operators may face unexpected
situations if the Energy quality is not under
control. Monitoring the Energy quality is then an
appropriate way to prevent such event and / or
to fix specific issues.
Intelligent equipment based architecture
This new architecture has appeared recently
due to Web technology capabilities, and can
really be positioned as an entry point into
monitoring systems. Based on Web
technologies it takes the maximum benefits of
standard communication services and
protocols, and license-free software.
The access to electricity information can be
done from everywhere in the site, and electrical
staff can gain a lot in efficiency.
Openness to the Internet is also offered for outof-site services.
Standard remote
Web browser
Internet
Standard local
Web browser
Intranet,
Ethernet TCP/IP
EGX400
Modbus serial link
Masterpact
Sepam
PM700
PM700
Altivar
"e-Support" becomes accessible
The setting up of an information system to
support a global Energy Efficiency approach
very quickly leads to economic gains, in general
with a Return on Investment (ROI) of less than 2
years for electricity.
An additional benefit, that is still underestimated
today, is the leverage in terms of Information
Technologies in the electrical sector.
The electrical network can be analyzed from
time to time by third parties – in particular using
external competencies via the internet for very
specific issues:
> Electricity supply contracts: changing of
supplier at a given point in time, e.g. permanent
economic analysis of the costs related to
consumption becomes possible without having
to wait for an annual review,
25
Energy Efficiency
> Total management of electrical data – via
internet – to transform it into relevant
information that is fed back via a personalized
web portal. Consumer usage information is now
a value-added commodity, available to a wide
range of users. It's easy to post customer
usage data on the Internet – making it useful to
the users is another matter,
> Complex electrical fault diagnosis to call in
an Electro-technical expert, a rare resource that
is easily accessible on the web,
> Monitoring of consumption and generating
alerts in the case of abnormal consumption
peaks,
> A maintenance service that is no more under
pressure on overheads, thanks to facility
management services.
Energy efficiency is no longer an issue that the
company has to face on its own. Many
"e-partners" can back-up the approach as
necessary, in particular when the measurement
and decision making assistance stage is
reached, on condition that the electrical
network is metered and communicative via
internet.
Implementation can be gradual, starting by
making a few key pieces of equipment
communicative and gradually extending the
system so as to be more accurate or to give
a wider coverage of the installation.
The company can choose its policy: ask one
or more partners to analyze the data, do it itself
or combine these options. The company may
decide to manage its electrical energy itself, or
ask a partner to monitor the quality and ensure
active monitoring of performances in terms of
aging.
Transparent Ready TM
Various resources are used to send data from
metering and protection devices installed in the
user’s electrical cabinets, e.g. via Schneider
Electric Transparent Ready™.
Electrical data recorded in industrial web
servers installed in electrical cabinets are sent
using the same standardized TCP/IP protocol in
order to limit the recurrent IT maintenance costs
that are intrinsic in an IT network. This is the
operating principle of Schneider Electric
Transparent Ready TM for communication of
data on Energy Efficiency. The electrical cabinet
is autonomous without the need for any
additional IT system on a PC, all of the data
related to Energy Efficiency is recorded and can
be circulated in the usual way via the intranet,
GSM, fixed telephone link, etc.
Solutions for energy savings
Here are presented a few solutions for reducing
the energy consumption in water applications,
without any significant change in the process.
Low-loss transformers and motors
A new generation of transformers and motors
built with high performance iron sheets and
increased cross section copper windings is now
available. The global efficiency may be
improved by up to 5%.
High Efficiency UV lamps
Ultraviolet (UV) radiation is a common method
used for disinfection in the wastewater
treatment plants due to its effectiveness at
inactivating most viruses and germs. Another
26
advantage in using UV disinfection is that it
eliminates the need to generate, handle,
transport or store toxic/hazardous or corrosive
chemicals. To produce UV radiation, lamps
containing mercury vapor are charged by
striking an electric arc. Low-pressure highintensity lamps are the more energy efficient
technology.
Variable Speed Drives
There is a great advantage to use Variable
Speed Drives (VSD) in pumping applications.
Indeed, if the driving motor is running at fixed
speed and the liquid flow is controlled via a
valve or throttle, electrical power is almost
constant, whatever the water flow.
On the opposite, by adjusting the rotation
speed with the valve or throttle fully open, the
absorbed electrical power is reduced by 50% at
80% of nominal flow for example.
Substantial energy savings are possible where
variable flow is needed.
MV motor supply
Where high power motors are requested
(> 100kW), the use of MV supply reduces the
line currents, thus reducing the Joule losses in
transformers, cables and motors. LV supply
may become cost-prohibitive because
equipment sizes get very large, limited or
unavailable, and multiple sets of cables are
needed.
For variable speed drives operating at MV, two
different configurations are possible:
> Variable speed drive operating directly at MV,
> Use of step-down / step-up transformers.
In this latter solution, the power electronic
circuits are operating at LV (400 or 690V).
Line
voltage
up to 6 kV
Step down
transformer
Inverter
Sinewave
motor filter
Step up
transformer
Medium
voltage
motor
L1
L2
ATV
M
L3
This solution has some significant advantages:
easy to install, well adapted to retrofit, no
change of motor necessary, low voltage
converter using well proven technologies
produced in large quantities, better availability
of spare parts, easier maintenance.
Schneider Electric VSD range dedicated to
pumping applications: ATV 21, ATV 61.
Eco8 software is proposed as a tool for
estimation of possible energy savings while
using Variable Speed Drives in pumping
applications.
In case of later change to low voltage motor,
the same inverter can be used.
Schneider Electric range of MV motor
controllers: Motorpact starters, Altivar variable
speed drives:
27
Energy Efficiency
Solutions for energy cost optimization
The objective is to reduce the cost of energy
utilized by different operations.
Power Factor Correction
The Power Factor (PF) is the ratio of the active
power to the apparent power absorbed by the
installation. (PF = kW / kVA).
Power Factor Correction (PFC) consists in
optimizing the Power Factor, i.e. setting its
value close to 1 (0.92 to 0.95 being a
reasonable value). A lower value means that
reactive energy must be supplied by the Utility
network, with consecutive increase of the line
demand current.
Power Factor Correction is generally managed
by implementation of capacitor banks.
Main features:
> Avoid charge of reactive energy (kvarh) by
the Utility,
> Reduce the demand current,
> Eliminate transformer over-sizing,
> Allow using the total system capacity,
> MV or LV connections are possible,
> Regulated or fixed batteries are adopted, for
fluctuating loads or not, respectively.
Schneider Electric solutions for Power Factor
Correction:
> MV equipment: CP••• range with Propivar
capacitors,
> LV equipment: Varset range with Varplus2
capacitors,
> Varlogic controller.
Harmonic management
In water installations, harmonics are mainly
generated by Variable Speed Drives, Ozone
generators, UV lamps, and should be carefully
managed when PFC capacitors are present, in
order to avoid resonance. Increased demand
current and nuisance tripping are the most
frequent adverse consequences of harmonics.
28
Harmonics should be managed in compliance
with the Utility regulations. Detuned capacitor
banks (anti-resonant) or filters can be
implemented locally (near the harmonic
generating equipment) or at the main
switchboard level (as a global solution).
Schneider Electric solutions:
> line reactors for Altivar range of VSD,
> ATV21 range with reduced harmonic
generation,
> Varset Harmony detuned capacitor banks
and Varset Filter passive filters,
> Active harmonic filters: Accusine, Sinewave.
Power monitoring
The implementation of power monitoring
devices follows 2 main objectives:
> Knowledge of the most power consuming
sectors,
> Follow-up of improvements in Energy
Efficiency.
The selection of measurement devices in
electrical equipment is made according to
the Energy Efficiency priorities and also the
available technologies:
> Measurement with simple “stand alone
product” solution.
Example:
PowerLogic PM700 measurement unit,
> Measurement capabilities provided by the
protection relays used in LV or MV electrical
networks.
Examples:
Sepam metering and protection relays,
Micrologic trip unit for Masterpact and
Compact circuit-breaker range,
TeSys U and TeSys T motor controllers,
Varlogic NRC12 capacitor bank controller.
> High performance metering units, separate
from the protection functions.
Example: PowerLogic Circuit Monitor.
Solutions for Availability & Reliability
Different possibilities for improving Availability &
Reliability of Power circuits are presented here.
Configuration of circuits
The following configurations are listed in the
order of increasing energy availability:
> Radial single feeder,
> Two-pole configuration (secondary selective),
> Double-ended power supply (primary
selective).
There is a great benefit to have the most critical
circuits configured with double-ended power
supply. The duration of any power supply
interruption will be limited to the operating time
of the Automatic Transfer Switch.
Back-up generators
The implementation of back-up generators is
very common in water treatment plants, where
water distribution cannot be interrupted for
periods longer than a few minutes. No
instantaneous take-over is necessary, as buffer
tanks are generally present.
Automatic transfer switches are naturally
associated with generators for rapid take-over
and smooth switch-back to normal supply.
Schneider Electric solutions:
> Compact, Masterpact circuit breakers with
UA or BA control unit
> Interpact switches,
> TeSys D and TeSys F contactors.
Here is a list of the main advantages provided:
> Less mechanical stress at motor start-up,
improving mechanical reliability,
> Controlled torque at motor stopping, avoiding
water-hammer and damaging of pipes,
> Power peak shaving, avoiding penalties,
> Reduced losses at motor start-up,
> No restriction on start-up number.
Schneider Electric solutions: Altistart ATS48,
Motorpact RVSS (Reduced Voltage Soft
Starter).
Protection coordination
Two examples of protection coordination
improving continuity of supply:
> discrimination between circuit breakers, such
that only the device just upstream of the fault
will trip, letting the other feeders still powered,
> coordination between circuit-breaker and
contactor for motor control, such that the
system remains operational after a fault is
eliminated (coordination type 2 according to IEC
60947-2).
Examples of Schneider Electric solutions:
> discrimination between Masterpact,
Compact and Multi9 ranges of circuit
breakers,
> coordination between Compact circuitbreakers and TeSys D / TeSys F motor
controllers.
Uninterruptible Power Supply
This type of equipment is essential for
continuous supply of process controllers,
monitoring and control rooms.
Schneider Electric solutions: Pulsar, Comet
UPS.
Soft starters
Soft starters are available in a wide range of
power, and are particularly suitable for water
applications like pumping. Multiplexing is
commonly used for cascading start-ups and
decelerations of multiple motors.
29
Preferred architectures
Introduction
The “preferred architectures” proposed by
Schneider Electric are directed to the design,
implementation and operation of water
infrastructure systems:
> with a high level of energy availability,
> which are profitable despite increasingly
constrained water prices,
> which are tailored to the present requirements
and expandable, in order to meet future
capacity demands and satisfy an increasing
severity of water quality regulations.
selection of equipment focused on optimized
Energy Efficiency.
Water industry plants being so diverse, the
“preferred architectures” should be considered
as examples of solutions. Single-line diagrams
are proposed for each of the installation types
presented earlier in this document. Illustrations
are given in order to focus on particular
equipment suitable to the considered type of
installation. The selection of equipment should
be adapted depending on country offer.
“Preferred architectures” include the
configuration of electrical installation and a
Remote lifting and pumping stations P1
Main characteristics
> 2 pumps,
> Typical power demand: 200kVA.
Diagram
Utility
Recommended configuration
> Because of limited power demand, a radial
single feeder configuration is proposed, with LV
supply by the Utility,
> All-in-one motor controllers are proposed for
compactness and simplified cabling.
Selection of Equipment
> TeSys U: direct on-line motor controllers,
> Universal Cabinet.
LVS
LVS: Low Voltage Switchboard
30
Pumping and small booster station P2
Main characteristics
> 4 pumps,
> Typical power demand: 500kVA.
Diagram
Recommended configuration
> Because of the limited number of motors, a
radial single feeder configuration is proposed,
with MV supply by the Utility.
Selection of equipment
> SM6 MV switchboard
> Trihal MV/LV transformer
> MotorSys Advanced iMCC with Prisma+
cabinet and TeSys U for fixed speed pumps
> ATV61 for variable speed pumps
> Varset capacitor bank.
31
Preferred architectures
Booster and complex pumping stations P3
Main characteristics
> More than 4 pumps,
> Typical power demand: 2500kVA.
Diagram
Recommended configuration
> For improved power availability, a MV supply
with ring main service by the Utility is proposed,
in addition to a LV back-up generator,
> A stepped capacitor bank is recommended
for Power Factor Correction, in order to deal
with the fluctuating demand power of large
motors.
Selection of equipment
> SM6 MV switchboard
> Trihal MV/LV transformer
> ATS48 soft-starters for fixed-speed motors
> ATV61 for variable speed pumps
> Varset capacitor bank.
Alternative
> Outdoor MV/LV prefabricated substation for
remote stations,
> Direct MV supply for large motors
(with Motorpact RVSS for example).
32
G
Autonomous water treatment plant T1
Main characteristics
> Typical power demand: 50kVA.
Recommended configuration
Diagram
Utility
> Because of limited power demand, a radial
single feeder configuration is proposed, with LV
supply by the Utility,
> Power monitoring is recommended for better
knowledge of fluctuations and analysis of
disturbances.
Selection of equipment
> TeSys U for fixed-speed pumps
> ATV61 for variable-speed pumps
> PM700 monitoring equipment
> Universal cabinet.
Alternative
> Supply by dedicated private network,
> Motor control with Altistart 48 soft-starters
Drinking water
- lifting
- screening
- clarifier
- aeration
- sludge
OR
Wastewater
- aeration
- flocculation
- filtering
- disinfecting
(to reduce in-rush currents in remote plants
with low fault level).
33
Preferred architectures
Drinking water treatment plant T2
Main characteristics
Selection of equipment
> Power demand: 125 to 1250 kVA.
> SM6 cubicle
> Trihal MV/LV transformer
> Universal cabinet
> Varset capacitor bank.
Recommended configuration
> For this range of power demand, a radial
single feeder configuration is proposed, with
MV supply by the Utility,
> All the process units are supplied from one
single LV switchboard,
> Power Factor Correction is needed because
of predominant motor load; a fixed capacitor
bank is adequate for simplicity.
Alternative
> Outdoor MV/LV prefabricated substation
> Prisma Plus switchboard
> Minera oil-immersed transformer
> Accusine active harmonic filter.
Diagram
Primary
treatment:
- pumping
- screening
34
- mixing
- flocculation
- sedimentation
Filtration
Tertiary
treatment:
- disinfecting
- distribution
Wastewater treatment plant T2
Main characteristics
Selection of equipment
> Power demand: 125 to 1250 kVA.
> SM6 cubicle
> Trihal MV/LV transformer
> Universal cabinet
> Varset capacitor bank.
Recommended configuration
> For this range of power demand, a radial
single feeder configuration is proposed, with
MV supply by the Utility,
> All the process units are supplied from one
single LV switchboard,
> Power Factor Correction is needed because
of predominant motor load; a fixed capacitor
bank is adequate for simplicity.
Alternative
> Outdoor MV/LV prefabricated substation
> Prisma Plus switchboard
> Minera oil-immersed transformer
> Accusine active harmonic filter.
Diagram
Primary
treatment:
- lifting
- screening
Biological
treatment
Sludge
processing
35
Preferred architectures
Drinking water treatment plant T3
Main characteristics
Selection of equipment
> Power demand: 1.25 to 5 MVA.
> SM6 cubicle
> Trihal MV/LV transformer / Canalis KTA /
Recommended configuration
> At this power level, an improved energy
availability is desirable, so a MV ring-main
service by the Utility is recommended,
> For improved redundancy, two independent
process lines are implemented, supplied by two
interconnected LV switchboards,
> In case of power interruption, the plant can
be supplied by back-up generators connected
at LV,
> Power Factor Correction can be managed
by stepped capacitor banks, well adapted
because large motors with fluctuating load
are present.
Prisma Plus switchboard
> Motorsys with Prisma Plus disconnectable
motor feeder
> Masterpact transfer switch
> Varset capacitor bank.
Alternative
> MV duplicate supply service
> Blokset switchboard
> Minera oil-immersed transformer
> Accusine active harmonic filter.
Diagram
G
Primary
treatment:
- screening
- aeration
36
- mixing
- flocculation
- sedimentation
Filtration
Tertiary
treatment:
- disinfecting
- distribution
Wastewater treatment plant T3
Main characteristics
Selection of equipment
> Power demand: 1.25 to 5 MVA.
> SM6 cubicle
> Trihal MV/LV transformer / Canalis KTA /
Recommended configuration
> At this power level, an improved energy
availability is desirable, so a MV ring-main
service by the Utility is recommended,
> For improved redundancy, two independent
process lines are implemented, supplied by two
interconnected LV switchboards,
> In case of power interruption, the plant can
be supplied by back-up generators connected
at LV,
> Power Factor Correction can be managed
by stepped capacitor banks, well adapted
because large motors with fluctuating load are
present.
Prisma Plus switchboard
> Motorsys with Prisma Plus disconnectable
motor feeder
> Masterpact transfer switch
> Varset capacitor bank.
Alternative
> MV duplicate supply service
> Blokset switchboard
> Minera oil-immersed transformer
> Accusine active harmonic filter.
Diagram
G
- lifting
- screening
Primary
treatment
Biological
treatment
Sludge
processing
37
Preferred architectures
Drinking water treatment plant T4
Main characteristics
Selection of equipment
> Power demand: 5 to 25 MVA.
> SM6 cubicle
> Sepam protection relays
> Trihal MV/LV transformer / Canalis KTA /
Recommended configuration
> For this type of large installation, an improved
energy availability is necessary, so a MV
duplicate supply service by the Utility is
recommended,
Okken switchboard
> Motorpact RVSS for MV motors
> Motorsys with Okken withdrawable motor
feeder
> In order to ensure the right level of
redundancy, the best adapted configuration is
an MV open ring within the plant,
> CP••• MV capacitor banks.
> The different process units are supplied at LV
> MV duplicate supply service with double
by separate transformers,
Alternative
busbar
> The largest motors can be supplied directly
at MV,
> Back-up generators are conveniently
connected at MV, because of the high power
level and the possibility to sell energy to the
Utility,
> RM6 Ring Main Unit (for severe environment)
> MCset: MV switchgear (for high short-circuit
current)
> Minera oil-immersed transformer
> Blokset switchboard.
> Power Factor Correction is provided by MV
capacitor banks.
Diagram
G
- screening
- aeration
38
- mixing
- flocculation
Sedimentation
Filtration
- disinfecting
- distribution
Wastewater treatment plant T4
Main characteristics
Selection of equipment
> Power demand: 5 to 25 MVA.
> SM6 cubicle
> Sepam protection relays
> Trihal MV/LV transformer / Canalis KTA /
Recommended configuration
> For this type of large installation, an improved
energy availability is necessary, so a MV
duplicate supply service by the Utility is
recommended,
Okken switchboard
> Motorpact RVSS for MV motors
> Motorsys with Okken withdrawable motor
feeder
> In order to ensure the right level of
redundancy, the best adapted configuration is
an MV open ring within the plant,
> CP••• MV capacitor banks.
> The different process units are supplied at LV
> MV duplicate supply service with double
by separate transformers,
Alternative
busbar
> The largest motors can be supplied directly
at MV,
> Back-up generators are conveniently
connected at MV, because of the high power
level and the possibility to sell energy to the
Utility,
> RM6 Ring Main Unit (for severe environment)
> MCset: MV switchgear (for high short-circuit
current)
> Minera oil-immersed transformer
> Blokset switchboard.
> Power Factor Correction is provided by MV
capacitor banks.
Diagram
G
- lifting
- screening
Primary
treatment
Biological
treatment
Chemical
treatment
Sludge
treatment
39
Preferred architectures
Desalination plant T3
Main characteristics
Selection of equipment
> Power demand: 10 to 50 MVA.
> MCset: MV switchgear(for high short-circuit
Recommended configuration
> For this type of large installation, service by
the Utility should be provided at HV,
> An improved energy availability is provided
by an MV duplicate supply service from the
Utility substation, and a double MV distribution
configuration,
> The different process units are supplied
at LV by separate transformers, with a doubleended LV distribution and interconnected MV
switchboards,
current)
> Trihal MV/LV transformer
> Motorpact RVSS for MV motors
> Sepam protection relays
> CP••• MV capacitor banks
> Okken LV switchboard with withdrawable
motor feeders
> Altivar 71 Variable Speed Drives (690V).
Alternative
> Minera oil-immersed transformer.
> The largest motors can be supplied directly
at MV,
> Power Factor Correction is provided by MV
capacitor banks.
Diagram
HP
pumps
HP
pumps
Booster
pumps
40
Booster
pumps
Pumping
screening
Chemical
treatment
Post
treatment
Annexes
Definition of Water and Wastewater functions
Lifting: raise of wastewater from the input pipe
up to the treatment plant level.
Screening: removal of objects (plastic bags,
cans, fruit rind, …) and floating fat.
Clarification: elimination of suspended solids
and floating substances.
Aeration: elimination of organic matter by
bacteria, favored by oxygenation. Elimination of
dissolved H2S and CO2.
Primary treatment: first stage of treatment,
basically: mechanical cleaning.
Flocculation: process by which fine particles
clump together by use of dedicated chemicals
(flocculent).
Filtering, filtration: elimination of solid particles
by flowing through a sand layer or porous
membrane.
Disinfecting: elimination of living organisms by
processes such as chlorination, exposure to UV
radiation or ozonation.
Sedimentation, clarification: following
flocculation, suspended solids are accumulated
at the bottom of the tank.
Tertiary treatment: final stage of treatment,
giving water the requested level of quality
before distribution or release in the natural
environment.
Sludge processing: transformation of solid
waste into valuable material (methane, fertilizer,
fuel) and unusable waste.
Distribution: delivery of drinking water through
booster or tower stations.
Chemical treatment: disinfecting by chemicals,
mainly chlorine.
Desalination (reverse osmosis): separation
process used to reduce the dissolved salt
content of saline water to a usable level. Water
from a pressurized saline solution is separated
from the dissolved salts by flowing through a
water-permeable membrane.
Biological treatment: elimination of organic
matter by bacteria.
Energy and Power for pumping applications
For pumping applications, the consumed
energy depends on the water quantity and
elevation between source and utilization point.
Theoretical formula:
Pu = ρ . g . Q . H
Pu : useful power (W)
ρ : volumic mass (1000 kg/m3)
Considering the efficiency of the motors and
pumps and the power losses in pipes and
valves, the order of magnitude of energy and
power are as follows:
> Average energy for 1m3 of water supply per
m: 5 Wh
> Average power for 1m3 per day of water
supply per m: (5 Wh)/24h ≈ 0,2 W/(m3 /day).
g : gravity constant (9.81 m/s2)
Q : flow rate (m3/s)
H : elevation (m)
The useful power Pu is then equal to 9810W for
a flow rate equal to 1m3/s, per m of elevation.
The corresponding energy is equal to 9810
joules, i.e. 2.725 Wh.
41
Annexes
Typical number of process units and different functions included
Drinking water
T1
T2
T3
T4
Raw water pump
Primary treatment
Primary treatment
Screening
Raw water tank
Screening
Screening
Aeration
Screening
Aeration
Aeration
Mixing
Mixing
Mixing
Flocculation
Flocculation
Flocculation
Sedimentation
Sedimentation
Unit 3
Filtration
Filtration
Sedimentation
Unit 4
Tertiary treatment
Tertiary treatment
Filtration
Disinfecting
Disinfecting
Distribution
Distribution
Process units
Unit 1
Sand filtration
Pure water tank + chlorine
Pure water pump
Unit 2
Unit 5
Disinfecting
Distribution
42
Wastewater treatment
T1
T2
T3
T4
Lifting
Lifting
Lifting
Lifting
Screening
Screening
Screening
Screening
Grit and fat removal
Primary treatment
Process units
Unit 1
Sand processing
Biological treatment
Secondary clarifier
Sludge pump
Sludge processing
Unit 2
Biological treatment
Primary treatment
Primary treatment
Unit 3
Sludge processing
Biological treatment
Biological treatment
Sludge processing
Chemical treatment
Unit 4
Unit 5
Sludge processing
Desalinating plant
T2 to T4
Only "reverse osmosis" is considered here,
as it is the most common and fastest growing
technology, spread all over the world.
Plant capacity is generally higher than
5000 m3 /day, so T1 is not relevant.
Process units
Unit 1
Pumping
Screening
Chemical treatment
Unit 2
Pressurization
Unit 3
Membrane separation
Brine discharge
Unit 4
Post treatment
Stabilization
Distribution
43
Annexes
Electrical installation characteristics
Here is a list of characteristics of Water industry
plants which have an impact on Electrical
Distribution architecture.
Site typology
Definition:
Type of plant, taking account of the number
of separate processing units and of the size of
the plant.
Different categories:
The previously mentioned classification of water
industry plants can be used:
> remote pumping station (P1 to P3)
> autonomous water treatment plant (T1)
> small water treatment plant (T2)
> medium water treatment plant (T3)
> large water treatment plant (T4)
Service reliability
Definition:
The ability of a power system to meet its supply
function under stated conditions for a specified
period of time.
Different categories:
> Minimum: this level of service reliability implies
risk of interruptions related to constraints that
are geographical (separate network, area
distant from power production centers),
technical (overhead line, poorly meshed
system), or economic (insufficient maintenance,
under-dimensioned generation).
> Standard.
> Enhanced: this level of service reliability can
be obtained by special measures taken to
reduce the probability of interruption
(underground network, strong meshing, dual
MV line, etc...).
Maintainability
Definition:
A system’s ability to be maintained (or returned
to a condition where it can fulfill the demanded
function), when a maintenance operation is
performed in accordance with a given
procedure using specific resources and during
a set period of time.
Different categories:
> Minimum: the plant must be stopped to
carry out maintenance operations.
> Standard: maintenance operations can be
carried out during plant operations, but with
44
deteriorated performance. These operations
must be preferably scheduled during periods
of low activity. Example: several transformers
with partial redundancy and load shedding.
> Enhanced: special measures are taken to
allow maintenance operations without
disturbing the plant operations.
Example: double-ended configuration.
Power demand
Definition:
The sum of the apparent load power (in kVA),
to which is applied a usage coefficient.
This represents the maximum power which can
be consumed at a given time by the installation,
with the possibility of limited overloads that are
of short duration.
Significant power ranges correspond to the
transformer power limits most commonly used.
The limits may be applicable to whole plants or
process units:
> < 250 kVA
> from 250 to 630 kVA
> from 630 to 2500 kVA
> > 2500 kVA
Load distribution
Definition:
A characteristic related to the uniformity of load
distribution (in kVA / m2) over an area or
throughout the plant.
Different categories:
> Uniform distribution: the loads are generally
of an average or low unit power and spread
throughout the surface area or over a large area
of the plant (uniform density). E.g.: small pumps.
> Intermediate distribution: the loads are
generally of medium power, placed in groups
over the whole plant surface area. E.g.: mixers.
> Localized loads: the loads are generally high
power and localized in several areas of the plant
(non-uniform density). E.g.: air blowers.
Power interruption sensitivity
Definition:
The aptitude of a circuit to accept a power
interruption.
Different categories:
> "Sheddable" circuit: possibility to be shut
down at any time for an indefinite duration
> Long interruption acceptable: interruption
time > 3 minutes *
> Short interruption acceptable: interruption
time < 3 minutes *
> No interruption acceptable.
*: indicative value, as supplied by standard EN 50160:
"Characteristics of the voltage supplied by public
distribution networks"
We can distinguish various levels of severity of
an electrical power interruption, according to
the possible consequences:
> No notable consequence,
> Interruption of process,
> Deterioration of the production facilities or
severe pollution of the environment,
> Causing danger for public health.
This is expressed in terms of criticality for
supplying loads or circuits.
> Non-critical: The load or the circuit can be
disconnected at any time ("load shedding").
E.g.: HVAC for control room.
> Low criticality: A power interruption causes
temporary interruption in the process, without
any financial consequences. Prolonging of the
interruption beyond the critical time can reduce
or stop the water delivery. E.g.: elevation
pumping station.
> Medium criticality: A power interruption cause
a short break in process or service. Prolonging
of the interruption beyond a critical time can
cause a deterioration of the water quality or a
cost for starting back-up generators. E.g.: Air
blower for biological treatment.
> High criticality: Any power interruption can
result in water quality deterioration and
unacceptable financial losses. E.g.: quality
control process, Information Technology (IT)
department, security department.
Disturbance sensitivity
Definition:
The ability of a circuit to work correctly in
presence of an electrical power disturbance.
A disturbance can lead to varying degrees of
malfunctioning. E.g.: operation halt or
deterioration, accelerated ageing, increase of
losses, etc
Types of disturbance with an impact on circuit
operations:
> Voltage sag,
> Over-voltage,
> Voltage distortion,
> Voltage fluctuation,
> Voltage imbalance.
Different categories:
> Low sensitivity: disturbances in supply voltage
have very little effect on operations. E.g.:
heating device.
> Medium sensitivity: voltage disturbances
cause a notable deterioration in operations.
E.g.: motors, UV lighting.
> High sensitivity: voltage disturbances can
cause operation stoppages or even the
deterioration of the supplied equipment.
E.g.: IT equipment, process control.
The sensitivity of circuits to disturbances
determines the design of shared or dedicated
power circuits. Indeed it is better to separate
“sensitive” loads from “disturbing” loads. E.g.:
separating lighting circuits from motor supply
circuits.
This choice also depends on operating
features. E.g.: separate power supply of lighting
circuits to enable measurement of power
consumption.
Disturbance capability of circuits
Definition:
The ability of a circuit to disturb the operation of
surrounding circuits due to phenomena such
as: harmonics, in-rush current, imbalance, High
Frequency currents, electromagnetic radiation,
etc.
Different categories:
> Non disturbing: no specific precaution to take
> Moderate or occasional disturbance: separate
power supply may be necessary in the
presence of medium or high sensitivity circuits.
E.g.: variable speed drives generating harmonic
currents.
> Very disturbing: a dedicated power circuit or
ways of attenuating disturbances are essential
for the correct functioning of the installation.
E.g.: motor with a high in-rush current.
Other considerations
> Environment. E.g.: lightning classification, sun
exposure,
> Rule of the Energy Distributor. E.g.: limits of
connection power for LV, access to MV
substation, etc…,
> Designer experience: consistency with
previous designs or partial usage of previous
designs, standardization of sub-assemblies,
existence of an installed equipment base,
> Load power supply constraints: voltage level
(230V, 400V, 690V), voltage system (singlephase, three-phase with or without neutral,
etc…).
45
Annexes
List of motor protection functions and result of activation
Short-circuit: disconnection in case of shortcircuit at the motor terminals or inside the motor
windings.
Thermal overload: disconnection of motor in
case of sustained operation with a torque
exceeding the nominal value. Overload is
detected by measurement of excessive stator
current or by using PTC probes.
Phase current imbalance: disconnection of
the motor in case of high current imbalance,
responsible for increased power losses and
overheating.
Phase current loss: disconnection of the
motor if one phase current is zero, as this is
revealing of cable or connection breaking.
Phase voltage loss: disconnection of motor if
one phase of the supply voltage is missing. This
is necessary in order to avoid a single-phase
running of a three-phase motor, which results in
a reduced torque, increased stator current, and
inability to start.
Ground fault: disconnection in case of a fault
between a motor terminal and ground. Even if
the fault current is limited, a fast action could
avoid a complete destruction of the motor.
Phase voltage reversal: prevent the
connection and avoid the reverse rotation of the
motor in case of a wrong cabling of phases to
the motor terminals, which could happen during
maintenance for example.
Long start: disconnection in case of a starting
time longer than normal (due to mechanical
problem or voltage sag) in order to avoid
overheating of the motor.
46
Motor stall: disconnection if the motor cannot
start, consecutively to a mechanical lock or
voltage sag, in order to avoid overheating of the
motor.
Jam: disconnection in order to avoid
overheating and mechanical stress if motor is
blocked while running because of congestion.
Voltage imbalance: disconnection of the motor
in case of high voltage imbalance, responsible
for increased power losses and overheating.
Low current or power: disconnection of the
motor in case of stator current lower than
normal, as this situation is revealing a pump
drain (risk of destruction of the pump) or broken
shaft.
Under-voltage: prevent the connection of the
motor or disconnection of the motor, as a
reduced voltage could not ensure a correct
operation of the motor.
Over-voltage: prevent the connection of the
motor or disconnection of the motor, as an
increased voltage could not ensure a correct
operation of the motor.
Load shedding: disconnection of the motor
when a voltage drop is detected, in order to
reduce the supply load and return to normal
voltage.
Low power factor: can be used for detection
of low power with motors having a high no-load
current.
Rapid cycle lock-out: prevent connection and
avoid overheating due to too frequent start-up.
Selection of LV switchboards
The selection of technological solutions is made
following the choice of single-line diagram and
considering to characteristics given below.
Examples of an operation event: turning off
a circuit-breaker, switching operation to
energize/de-energize a machine.
Environment, atmosphere
Example of a maintenance operation: tightening
connections.
A notion taking account of all of the
environmental constraints (average ambient
temperature, altitude, humidity, corrosion, dust,
impact, etc.) and bringing together protection
indexes IP and IK.
Different categories
Example of an upgrade operation: connecting
an additional feeder.
There are a limited number of relevant service
ratings (see following table).
> Standard: no particular environmental
The types of electrical connections of functional
units can be denoted by a three-letter code:
constraints
> the first letter denotes the type of electrical
> Enhanced: severe environment, several
environmental parameters generate important
constraints for the installed equipment
> the second letter denotes the type of
connection of the main incoming circuit,
> Specific: atypical environment, requiring
electrical connection of the main outgoing
circuit,
special enhancements.
> the third letter denotes the type of electrical
connection of the auxiliary circuits.
Service Rating
The service rating (IS) is a value that allows us
to characterize an LV switchboard according to
user requirements in terms of operation,
maintenance, and scalability. The different index
values are indicated in the following table.
The following letters shall be used:
> F for fixed connections,
> D for disconnectable connections,
> W for withdrawable connections.
Operation
Maintenance
Upgrade
Level 1
IS = 1 • •
Operation may lead to
complete stoppage of
the switchboard
IS = • 1 •
Operation may lead to
complete stoppage of
the switchboard
IS = • • 1
Operation may lead to
complete stoppage of
the switchboard
Level 2
IS = 2 • •
Operation may lead to
stoppage of only the
functional unit
IS = • 2 •
Operation may lead to
stoppage of only the
functional unit, with
work on connections
IS = • • 2
Operation may lead to
stoppage of only the
functional unit, with
functional units provided
for back-up
Level 3
IS = 3 • •
Operation may lead to
stoppage of the power of
the functional unit only
IS = • 3 •
Operation may lead to
stoppage of only the
functional unit, without
work on connections
IS = • • 3
Operation may lead to
stoppage of only the
functional unit, with
total freedom in terms of
upgrade
47
Annexes
Service ratings are related to other mechanical
parameters, such as the Protection Index
(IP),form of internal separations, the type of
connection of functional units or switchgear:
Service
rating
Protection
index IP
Form
Functional Unit
withdrawability
111
2XX
1
FFF
211
2XB
1
FFF
223
2XB
3b
WFD
232
2XB
3b
WFW
233
2XB
3b
WWW
332
2XB
3b
WWW
333
2XB
3b
WWW
Definition of the protection index: see IEC
60529: "Degree of protection given by
enclosures (IP code)",
Definitions of the form and withdrawability: see
IEC 60439-1: "Low-voltage switchgear and
controlgear assemblies; part 1: type-tested and
partially type-tested assemblies".
48
Maquette Jack Grison / Impression LM Graphie
Schneider Electric SA
89 boulevard Franklin-Roosevelt
F-92505 Rueil-Malmaison Cedex (France)
Tél : +33 (0) 1 41 29 70 00
http://www.schneider-electric.com
October 2008
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