01
Protection Relays
MiCOM P746
Numerical Busbar Protection
The MiCOM P746 centralised numerical busbar protection provides
complete protection for all voltages level up to extra voltage busbar
configurations.
Proven techniques, and dynamic topology processing algorithms, offer a
combination of security, speed and high sensitivity.
With a typical operating time of 12 ms with HB/ HS contact option or 17 ms
with standard contacts, the P746 protection is one of the fastest in its class.
P746 in 80TE
Moreover, the trips can be synchronous or sequential.
Fully communicant with IEC61850-8.1, Courier, DNP3.0, Modbus and
IEC103 protocols, the P746 is easily integrated in any substation system.
The substation replica processing algorithms ensure that the P746 adapts to
the dynamically changing topology of the busbar which is displayed on any
PC with the substation real time dynamic monitoring tool.
Customer benefits
• Fast fault trip (typically 12 or 17 ms)
• Synchronous or Sequential trip
• Adapted to simple busbar
configurations
• IEC61850-8.1 compliant
• Can operate with different types of CT
• Programmable function keys, hotkeys
and tri-colour LEDs.
The MiCOM P746 differential busbar protection provides a centralised one
box or three boxes architecture and is very simple to use: It does not need
to be deeply engineered and supports easy operation and maintenance of
the busbar.
Application
The MiCOM P746 centralized numerical busbar protection has been
designed to protect a wide range of busbar configurations:
• One box mode - P746
• Three boxes mode – one P746 per phase
In the three boxes mode, the units are totally independent and not linked to
each other.
The MiCOM P746 can accommodate up to 2 Zones plus Check Zone for
1 or 3 boxes mode and up to 4 Zones for dual 1 or 3 boxes modes:
• 1 VT, up to 6 CTs, 6 Breakers and 12 Isolators with the
One box mode solution
• 2 VTs, up to 12 CTs, 12 Breakers and 14 Isolators with the
Dual One box mode solution
• 2 VTs, up to 18 CTs, 18 Breakers and 36 Isolators with the
Three boxes mode solution
• 2 VTs, up to 36 CTs, 36 Breakers and 72 isolators with the
Dual Three boxes mode solution.
Protection Relays
02
MiCOM P746
The MiCOM P746 is associated with each CT
location, usually one per incomer/feeder and one
or two for each bus coupler/bus section. The
MiCOM P746 acquires the analogue signals from
the associated CT and the binary signals from
the auxiliary contacts of the circuit breakers and
isolators.
Feeder
Feeder
CT
CT
CB
CB
Q
Q
Q
The MiCOM P746 also incorporates the main
circuit breaker failure logic together with
additional protection functions (Dead zone,
overcurrent, etc...). The P746 particularly useful
in double busbar applications allows high
number of opto inputs (up to 40) and relay
outputs (up to 32), function keys and Ethernet
or second rear port board option.
Topology scheme examples
CB
CT
Q
Q
Q
CB
CB
CT
CT
Feeder
Feeder
Feeder
Feeder
CT
CT
CB
CB
Q
Q
Q
Feeder
Feeder
CT
CT
CB
CB
Q
CB
CT
Q
Q
Q
Q
CB
CB
CB
CT
CT
CT
Feeder
Feeder
Feeder
Q
Q
Q
Q
Q
Q
CB
CB
CB
CB
CT
CT
CT
CT
Feeder
Feeder
Feeder
Feeder
Feeder
Q
CT
Q
Feeder
Q
CB
Q
Q
Q
Q
Q
Q
CB
CB
CB
CB
CT
CT
CT
CT
Feeder
Feeder
Feeder
Feeder
Cost optimised
to suit simple busbar
configuration
Q
Q
Q
Q
Q
Q
CB
CB
CB
CB
CT
CT
CT
CT
CT
Feeder
Feeder
Feeder
Feeder
Feeder
CB
Q
Q
Q
Q
Q
Q
Q
Q
CT
CT
CB
Q
CB
Q
CT
CT
Q
CB
CB
CB
CB
CB
CT
CT
CT
CT
Feeder
Feeder
Feeder
Feeder
Q
Q
Q
CB
CB
CB
CT
Feeder
CT
Feeder
Feeder
CT
CT
CT
CB
CB
CB
Q
Q
Q
Protection Relays
03
MiCOM P746
ANSI
IEC 61850
FEATURES
87BB / P
PhsPDIF
87CZ / P
CzPPDIF
50/51/P
50/51/N
50ST / P
50ST / N
CTS
VTS
50BF
OcpPTOC
EfmPTOC
DzpPhsPTOC
DzpEfmPTOC
Phase segregated biased current differential high speed busbar protection
Check Zone segregated biased phase current differential high speed busbar
protection
Phase overcurrent protection (2 stages)
Earth overcurrent protection (2 stages)
Dead zone phase protection (short zone between CTs and open CBs)
Dead zone earth protection (short zone between CTs and open CBs)
Current transformer supervision
Voltage transformer supervision
Breaker failure protection (LBB)
ISL Isolator discrepancy alarm
Digital inputs
Output relays
Front communication port (RS232)
Rear communication port (Kbus/EIA(RS)485)
Second Rear communication port (Kbus/EIA(RS)485) *
Rear communication port (Ethernet) *
Time synchronisation port (IRIG-B) *
Function keys
Programmable tri-colour LEDs
RBRF
OptGGIO
RlyGGIO
FnkGGIO
LedGGIO
P746
•
•
•
•
•
•
•
•
•
•
16 to 40*
16 to 32*
•
•
Option
Option
Option
10
18
* Refer data sheet for model selection
Functional Overview
(Description of ANSI code nos., see Protection Function Overview)
/
/
Remote
comm. port
Local
Communication
Fault Records
Disturbance
Records
Measurements
Self Monitoring
X
87BB
/P
87CZ
/P
50/
51/P
50/
51/N
Binary
Input / output
50ST
50BF
PS L
CTS
VTS
LEDs
ISL
Busbar Protection Scheme
P746
Protection Relays
04
MiCOM P746
Management functions
In addition to the protection and control elements,
the P746 provides a wide range of measurement,
monitoring, post fault analysis and self-diagnostic
features:
Busbar differential protection
The primary protection element of the P746 is the phase segregated biased
current differential protection. The technique is based on the numerical
application of Kirchoff’s Law for the selective detection and high-speed
isolation of a faulty section of the busbar.
To ensure adaptability of the relay to any type of busbar configuration the
P746 is built with a universal topology processing algorithm. This algorithm
determines the optimum tripping zone based on the current status of the
plant isolators or/and circuit breakers.
• Trip circuit supervision (using PSL)
• On-line measurement
• Plant status monitoring
• 4 alternative setting groups
• Programmable logic (PSL)
• Sequence of event recording (SOE)
• Comprehensive Fault record
• Comprehensive disturbance recording
(waveform capture)
• User configurable function keys & hotkeys
• User configurable tri-colour LEDs
• Local and remote communication ports
• Time synchronisation
• Fully customisable menu texts
• Multi level password protection
• Test facilities
• Power-up diagnostics and continuous selfmonitoring of relay.
• User friendly setting, analysis and monitoring
software
X
X
X
X
X
Universal on-line topology processing
The P746 employs biased differential algorithms, in which the differential
current is compared with a bias current. This characteristic ensures stability
of the protection for external faults even with differing CT tolerance and
errors which could lead to spurious operation.
To increase the security of the differential protection, the biased differential
element is supervised by a biased global Check Zone element. This
ensures stability even under erroneous status of the auxiliary contact of
plant isolators and circuit breakers.
The MiCOM P746 also employs CT supervision and an innovative external
fault detection algorithm: the current phase comparison. This ensures
stability when CTs become saturated. This technique is heavy CT saturation
proof and still trip on evolving to internal fault..
Bias differential characteristics
i diff (t)
i diff (t)
Tripping
Area
k2
0
=2
to
k=
I D CZ>2
I D >2
o
k1 = 0 t
I D >1
%
90
o
0t
Tripping
Area
0%
9
N
k2
Restrain
Area
=0
to
%
90
kN
=
I D NCZ>2
I D N>2
50%
kN1 = 0
I D N>1
o
0t
Restrain
Area
to 50%
i bias (t)
X
i
X
Differential current :
X
1
X
i
3
X
i
i
2
n
Operating current :
Bias current :
%
90
iN bias (t)
i diff node (t)
i2
+
i diff (t) = i diff node (t)
=
i bias (t)
=
i1
=i +
1
+
i2
+
i3 + ....... + i n
i
i3
+ ....... +
in
=
in
Protection Relays
05
micom P746
multiPle tRiPPing cRiteRiA
The MiCOM P746 maintains the highest level of
stability under all conditions including hardware
failure and incoherent signals applied from
external plant or generated by the power system.
Any tripping order must therefore be made
conditional on the simultaneous occurrence of
at least 5 criteria:
Magnitude Criteria: Confirmation of Two
Simultaneous Thresholds per Zone:
• Exceeding the bias slope characteristic (k2)
• Exceeding differential operating current
threshold (ID>2).
Check Zone Supervision
The zone element(s) are only permitted to trip if
the order is confirmed by the check zone element:
• Exceeding the bias slope characteristic (kCZ)
• Exceeding differential operating current
threshold (IDCZ>2)
continuous suPeRvision of cuRRent ciRcuits
The P746 detects any abnormality in the current circuit by continuously
monitoring it. Under normal operating conditions the differential current will
be negligible. An anomaly is detected by a threshold, ID>1, which can be
set to alarm from 10 A primary.
continuous suPeRvision of cuRRent tRAnsfoRmeRs
The P746 detects abnormality in any current transformer by continuously
supervising them.
DiffeRentiAl cuRRent setting
When switching operations are carried out in the substation, incorrect
topology replicas may occur.
In this case, a differential current appears. The differential elements of the
MiCOM P746 are allowed to operate only if the differential current reaches
a threshold ID>2 which is normally set above the highest load current when
no voltage criteria is used.
PHAse oveRcuRRent AnD eARtH fAult PRotection
Current Phase Comparison Criteria
Optional Voltage Criteria:
• Undervoltage U< OR, V1< OR
• Negative sequence overvoltage V2> OR
• Zero sequence overvoltage 3V0>
sYncHRonous oR seQuentiAl
tRiPPing
The MiCOM P746 allows delaying all or each
tripping contact.
That is highly recommended for high speed
disconnection of the bar from grid and delayed
trip of the generation feeders
DeAD Zone oR blinD sPot PRotection
The current transformers or the open isolators
surrounding the busbars define the limits of the
main zones. When a feeder isolator is opened
a dead zone or blind spot is created to the
associated CT. The MiCOM P746 detects this
condition automatically and provides protection
for this zone also.
One stage of definite time delayed overcurrent
and earth fault protection is provided in each
Peripheral Unit to provide this functionality.
Two independent stages of phase overcurrents and earth fault protection
are provided in the MiCOM P746. These elements provide additional
protection for the individual circuits. The two stages can be programmed as:
• First stage can be programmed as definite time (DT) delay or one of the
nine inverse time (IDMT) curves (IEC/UK and IEEE/US).
• Second stage can only be programmed as definite time.
ciRcuit bReAkeR fAiluRe PRotection (lbb )
The P746 offers an in-built integrated solution for breaker failure protection.
In general the Breaker Failure protection is executed on a per phase basis
which involves the possibility of receiving tripping orders on a per pole
basis.
The MiCOM P746 busbar protection can also work in co-ordination with
external breaker failure protection relays. In this configuration, the receipt of
an external breaker failure command results in tripping of all the adjacent
circuit breakers, via the topological recognition system knowing which
breaker is connected to which zone.
Dead zone protection
BB1
Isolator closed
CB open
Isolator closed
CB open
Dead Zone
P746
Feeders not connected
Dead Zone
Protection Relays
06
MiCOM P746
Current transformer mixing correction
The MiCOM P746 can correct a mix between current transformer ratios over
a very wide range up to 20. Its associated user interface provides a range
between 1 A and 30 000 A primary.
Since the current transformer ratings in a substation may be of mixed
ratios, the MiCOM P746 uses a virtual CT ratio equal to a settable reference
current/1, irrespective of the feeder section concerned.
Remote HMI
The real time Remote HMI software allows the
user to monitor the position of CBs and isolators
in the busbar scheme, as well as currents,
alarms, etc...
Isolation and maintenance operating mode
For ease of operation or maintenance of the busbar protection system, the
MiCOM P746 can receive specific commands designed to allow system
testing or other intervention without any danger of unwanted tripping.
In the MiCOM P746, a centralised command to isolate the busbars can be
selectively applied per zone:
• Differential protection (87BB) and Circuit Breaker Failure protection (50BF)
blocked. The additional local protection functions (51, 51N, etc...) remain
operational.
Cct Fail CZ Alm
DDB #469
Cct Fail Z1 Alm
DDB #467
1
Cct Fail Blk Z1
DDB #843
Cct Fail Blk CZ
DDB #848
&
Reset CcT Fail
DDB #892
Function Key 8
DDB #359
Function Key 2
DDB #353
Diff CZ Blked
DDB #1820
Function Key 9
DDB #360
FnKey LED8 Red
DDB#222
NonLatching
FnKey LED2 Red
DDB#210
NonLatching
FnKey LED7 Red
DDB#220
NonLatching
FnKey LED9 Red
DDB#224
FnKey LED8 Grn
DDB#223
1
FnKey LED2 Grn
DDB#211
Set Z2 Test Mode
DDB #711
Z2 In Test Mode
DDB #1697
Diff CZ Blked
DDB #1820
NonLatching
Set Z1 Test Mode
DDB #710
Z1 In Test Mode
DDB #1696
Function Key 7
DDB #358
MeaSurement and recording
facilities
&
1
1
Remote HMI
The P746 is capable of measuring and storing
the values associated with a fault. All the events,
faults records and disturbance records are time
tagged to 1 ms using an internal real time clock.
An optional IRIG-B port is also provided for
accurate time synchronisation. A lithium battery
provides a back up for the real time clock and all
records in the event of supply failure.
FnKey LED7 Grn
DDB#221
Reset Relays/LED
DDB #876
FnKey LED9 Grn
DDB#225
Programmable scheme logic (MiCOM S1 Studio- PSL Editor)
Measurements
The measurements provided, which may be
viewed in primary or secondary values, can be
accessed via the back lit liquid crystal display.
Programmable scheme logic
They are also accessible via the communication
ports. The following instantaneous parameters
can be viewed:
Plant statuS
MiCOM P746
• Phase current magnitude IA and/or IB
and/or IC
• Phase current angle IA and/or IB and/or IC
• Voltage magnitude and angle
• Frequency
• Differential current Idiff / phase / zone
• Bias current Ibias / phase / zone
• Check zone Idiff / phase
• Check zone Ibias / phase
Powerful programmable logic (PSL) allows the user to customize the
protection and control functions. It is also used to programme the
functionality of the optically isolated inputs, relay outputs and tri-colour
LED indications. The programmable logic comprises of gate logic and
general purpose timers. The gate logic includes OR, AND and majority
gate functions, with the ability to invert the inputs and outputs, and provide
feedback. The programmable logic is configured using the graphical
MiCOM S1 Studio PC based support software
Checks and monitoring of the plant status can be made and an alarm
raised for any discrepancy condition between the open and closed auxiliary
contacts of the isolators and circuit breakers.
Protection Relays
07
MiCOM P746
Event recorder
Up to 512 time tagged event records are stored in battery backed memory,
and can be extracted via the communication port or be viewed on the front
panel display.
Fault recorder
Records of the last 5 faults are stored in the battery backed memory.
Each fault record includes:
Local and remote
communications
Two communication ports are available
as standard; a rear port providing remote
communications and a front port providing local
communications.
As option either a second rear port or an Ethernet
board (to use the IEC61850-8.1 protocol) can be
added .
• Faulted phase
• Indication of the faulty zone
• Date and time
• Active setting group
• Fault duration
• Currents, frequency and voltage
The front RS232 port has been designed
for use with MiCOM S1 Studio, which fully
supports functions within the relay by providing
the ability to programme the settings off-line,
configure the programmable logic, extract
and view event, disturbance and fault records,
view the measurement information dynamically
and perform control functions (using Courier
protocol).
Disturbance recorder
The default remote communications is Courier /
RS 485 or K-bus but IEC60870-5-103 or Modbus
or DNP 3.0 can be selected.
• Specific analogue channels
• VAN, VBN and VCN
• IA, IB, IC for each CT in 1 box mode
• Ix1 to Ix18 (x is A or B or C) in 3 box mode
• Maximum duration of one record and number of records
• Up to 10.5s per record and minimum of 50 records 1.5s (memory of 75s)
An optional second rear courier communications
port is available which may be configured
as RS232, RS485 or K-Bus. IEC 61850 is
available when the optional Ethernet port is
ordered. IEC 61850-8.1 offers high-speed
data exchange, peer-to-peer communication,
reporting, disturbance record extraction and time
synchronisation.
The MiCOM P746 has independent disturbance recording facility. It can
record 18 analogue and 32 digital channels in addition to 1 time channel.
Disturbance records can be extracted from the relay via the remote
communications and saved in the COMTRADE format. These records may
be examined using MiCOM S1 Studio or any other standard COMTRADE
viewer.
Disturbance record viewed in MiCOM S1 Studio
Diagnostics
Automatic tests performed including poweron diagnostics and continuous self-monitoring
ensures a high degree of reliability. The results
of the self-test functions are stored in battery
backed memory. Test features available on
the user interface provide examination of input
quantities, states of the digital inputs and
relay outputs. A local monitor port provides
digital outputs, selected from a prescribed list
of signals, including the status of protection
elements.
Fast, Sensitive & Secure:
P746 the Centralised Solution
for Busbar Protection
Protection Relays
08
MiCOM P746
Hardware
The MiCOM P746 includes:
• A back-lit liquid crystal display
• LEDs: 18 tri-color
• Function keys
• Hotkeys
DEVICE Track record
• RS232 (front port) & RS485 / K-bus (rear port)
• Optional Second rear communication board
• Optional IRIG-B port
• Download/monitor port
• Battery (supervised)
• N/O and C/O watchdog contacts
• Supervised +48 V field voltage
• CT inputs 1A and 5A
• Universal opto inputs with programmable
voltage threshold
The optically isolated inputs are independent and
may be powered from the +48V field voltage.
• Over 200 DIFB, medium impedance
biased differential busbar protection
scheme delivered since its launch in
1992.
• Medium impedance biased differential
busbar protection with linear current
combination, DIFB CL, launched in 1996.
Over 70 cubicles delivered.
• Since the launch of the P740, over 800
systems have been delivered
• Since the launch of the P746, over 350
relays have been delivered.
Schneider Electric Industries SAS
35, rue Joseph Monier
CS 30323
F - 92506 Rueil Malmaison Cedex (France)
Tel.: +33 (0) 1 41 29 70 00
RCS Nanterre 954 503 439
Capital social 896 313 776 €
www.schneider-electric.com
NRJED111065EN
As standards, specifications and designs change from time
to time, please ask for confirmation of the information given
in this publication.
Design: Schneider Electric Industries SAS - Sonovision
Photos: Schneider Electric Industries SAS
Printed: Altavia Connexion - Made in France
This document has been
printed on recycled paper.
05-2011
ART838338 © 2011 Schneider Electric Industries SAS - All rights reserved
• Optional Ethernet rear communication board or