Protection Relays
01
MiCOM P122C
Time-Overcurrent Protection
The Micom P122c is a compact unit for nondirectional time-overcurrent protection. It
is designed for the selective short-circuit
protection of high- and medium voltage
networks as well as for the overload protection
of transformers, overhead lines and cables.
In addition to a wide spectrum of protection
functions, a number of supervision functions are
available, including circuit breaker supervision.
Thanks to the provision of two setting groups,
the P122C is readily adapted to varying
conditions in system operation.
Customer Benefits
•1A/5A software setting
•4 function keys
•Compact unit for flush and wall-surface mounting
•Comprehensive measurements
•Disturbance and event recording
The intuitive user interface together with
the easily accessible PC interface allow
straightforward yet comprehensive setting
as well as access to readings from extensive
recordings. Interfacing to substation control
or the SCADA system is readily accomplished
using the optional communication interface and
a communication protocol selected to suit the
application.
Four function keys at the front panel provide
user-friendly handling and rapid access to data
and control operations such as manual closing
and opening of the circuit breaker.
For extra flexibility, the compact housing is suitable
for either flush- or wall-surface mounting.
Protection Relays MiCOM P122C
02
Application
Global functions
One of the major applications of the MiCOM
P122C non-directional time-overcurrent protection
unit is the selective short-circuit protection of
radial networks with single-side infeed and of
open ring systems.
The following global functions are generally
available in the P122C:
Alternatively, the P122C provides back-up
protection for differential protection units.
Furthermore, the P122C offers preventative
protection based on its thermal overload and
unbalance protection functions. Applications
of these functions to lines, cables, motors and
transformers are fully supported for short-circuit,
overload and unbalance protection.
•
•
•
•
Setting groups
Measured data acquisition
Event counters (with trip statistic)
Event recording (signal recording with
real-time stamp)
• Fault recording
• Startings recording
• Disturbance recording
(CT inputs and binary events)
Functions Overview
P122C
50/51
Three-phase overcurrent protection
•
50N/51N
Earth fault overcurrent protection
•
46
Unbalance protection
•
49
37
50BF
50/27
86
Thermal overload protection
Loss of load protection
Circuit breaker failure protection
Switch on to fault protection
Output relay latching
•
•
•
•
•
Cold load pick up
•
Setting groups
•
Blocking logic
•
Logic selectivity
Circuit breaker supervision
•
•
Trip circuit supervision
•
Broken conductor / CT circuit supervision
Self monitoring
Measured data acquisition
Peak and rolling values
Event recording
Fault recording
Startings recording
•
•
•
•
•
•
•
Disturbance recording
•
46BC
Communication interface (RS 485 or fibre optics
Protocol for communication interface:
IEC 60870-5-103 or Modus RTU
Function keys
Binary inputs
Output relays
MiCOM P122C provides a wide
range of protection functions
option
•
4
2 (opt. 7)
8
Protection Relays MiCOM P122C
03
Main functions
The protection and supervision functions can
be individually configured or disabled to suit a
particular application. Settings of functions that
are not required and have been disabled by
the user are hidden (except for the selection
parameter). Functional support is withdrawn from
these hidden settings.
This concept permits an extensive scope of
functions and universal application of the device
in a single design version, while at the same time
providing for a clear and straight-forward setting
procedure and adaptation to the protection and
control task under consideration
Simple function selection by mouse click
Function diagram
PC
Interface
Communication
to setting
program S1
Communication
Interface
to SCADA / Substation control...
via RS485 or Fibre Optics
using IEC 60870-5-103 or Modbus
Further Functions
Measurements
Cold load pick-up
Blocking logic
Logik selectivity
Circuit breaker supervision
Trip circuit supervision
Self monitoring
Function keys
...
Phase and residual currents
Direct and Inverse currents
Max. Phase current storaged
Peak and Rolling values
Frequency
Thermal state
CB operating times
...
Recordings
Event rec.
Starting rec.
.
Fault rec.
Disturbance rec.
50/51
50N/51N
46
49
37
50BF
50/27
46BC
86
I
Always
Available
(Description of ANSI code No. see Functions Overview)
Option
Time-Overcurrent Protection
P122C
Protection Relays MiCOM P122C
Three-phase overcurrent protection
(50/51)
The overcurrent protection for phase faults
comprises three stages; each stage is provided
with separate startings for the three phases.
The first two stages can be operated as either inverse-time (IDMT) or definitetime (DTOC)
stages. For the IDMT mode, a multitude of tripping
characteristics is offered for selection. The third
stage operates as a definite-time (DTOC) stage.
For a detection of intermittent faults the first two
stages are additionally equipped with hold-time
logic (reset timer).
04
Nr.
Tripping time char.
Constants and formulas (t in s)
( k = 0.03...4.00)
a
b
STI
Short time inverse
0,05
0,04
SI
Standard inverse
0,14
0,02
VI
Very inverse
13,50
1,00
EI
Extremely inverse
80,00
2,00
LTI
Long time inverse
120,00
1,00
RC
Rectifier protection
45900
5,60
1)
c
R
t=
a
k
b
I
I ref
–1
(SI, VI, EI and LTI according to IEC 255-3)
Earth fault overcurrent protection
Tripping
(50N/51N)
The overcurrent protection for earth faults
comprises three stages. The first two stages can
be operated as either inverse-time (IDMT) or
definite-time (DTOC) stages. For the IDMT mode,
a multitude of tripping characteristics is offered for
selection. The third stage operates as a definitetime (DTOC) stage.
For a detection of intermittent faults the first two
stages are additionally equipped with hold-time
logic (reset timer). Additionally the first stage when in DTOC mode - is optionally provided with
a second hold-time logic. This effects a pulse
prolongation of the starting signal.
For specific applications a high, standard or
sensitive setting range can be ordered for the
earth fault stages. The effect of the earth fault
stages on the formation of the general starting
signal can optionally be suppressed. This will
then automatically inhibit the formation of the trip
command by the earth fault stages.
Unbalance protection (46)
The current unbalance protection, based on the
evaluation of the negative-sequence current,
comprises two stages. The first stage can be
operated as either an inverse-time (IDMT) or a
definite-time (DTOC) stage. For the IDMT mode,
a multitude of tripping characteristics is offered
for selection. The second stage operates as a
definite-time (DTOC) stage.
MiCOM P122C for rapid and selective
fault clearance in your power system
Reset
MI
Moderately inverse
0,0515
0,02
0,1140
4,85
VI
Very inverse
19,6100
2,00
0,4910
21,60
EI
Extremely inverse
28,2000
2,00
0,1217
29,10
C02
Short time inverse
0,00342
0,02
0,00242
2,226
C08
Long time inverse
5,95
2,00
0,1800
5,98
t = k
a
b
I
I ref
+c
–1
t
r=
R
k r
1
–
I
2
I ref
(MI, VI and EI according to ANSI/IEEE C37. 112)
RI
RI -type inverse
t=
1
k
0,339
–
0,236
(k=0,05...10,00)
I
Iref
For all the characteristic curves additionally a reset timer with a definite time
characteristic is available
t r = Reset - time
1) Available for Overcurrent Phase and Earth
Tripping time characteristics
For a detection of intermittent faults the first stage is additionally equipped
with hold-time logic (reset timer). The effect of the negative-sequence
current stages on the formation of the general starting signal can optionally
be suppressed. This will then automatically inhibit the formation of the trip
command by the negative-sequence current stages
Protection Relays MiCOM P122C
05
Thermal overload protection(49)
Cold load pick-up
This function provides thermal overload protection
for overhead lines, cables and transformers.
The maximum value of the three phase currents
is used to track a first-order thermal replica
according to DIN IEC 255-8. The tripping time is
determined with the help of the preset thermal
constant t of the object to be protected, the preset
tripping limit θ Trip and the preset overload factor
k and is dependent on the accumulated thermal
load θp:
during cold load pick-up the current thresholds
of the overcurrent and unbalance protection as
well as the current threshold of the overload
protection can be raised for a configurable period
of time. The cold load pick-up function can be
triggered optionally via a binary input signal or a
settable current stage. This function can be used
to avoid unwanted trips caused by shortterm
increases in load e.g. when energizing a motor or
a transformer.
1
0,339 –
0,236
I
(k=0,05...10,00)
Iref
An initial warning can be issued when the preset
threshold θWarning is exceeded
Loss of load protection (37)
a loss of load can be detected via a definite-time
delayed undercurrent stage. The function is
inhibited when the feeder is switched off. The
recognition of the switched-off feeder takes place
optionally via status of the CB auxiliary contact
or a settable current criterion.
Circuit breaker failure protection (50bf)
a timer is started by the trip command. While
the timer is running, the amplitudes of the three
phase currents are monitored. Their values below
a configurable threshold are used as a criterion
for the detection of open circuit breaker poles. If
the set condition is not met when the timer stage
has elapsed, a signal is issued to indicate that the
circuit breaker has failed to clear the fault.
The receipt of this signal from a downstream
relay at an appropriately configured logic input in
combination with the persisting general starting
leads to the generation of an instantaneous trip
signal.
Switch on to fault protection
while switching on the circuit breaker it can
happen that due to a remaining feeder earthing
the circuit breaker erroneously switches on to
a fault. This function provides an instantaneous
protection trip during a settable time after the
issue of the Manual-close command. According
to the operating mode a trip command is issued
either via a general starting signal or via one of
the phase current stage startings.
Blocking logic
via two independent binary inputs various time
stages e.g. for the individual overcurrent - and
unbalance protection can be blocked externally.
This is controlled via a matrix for the selection of
the timers to be taken into account for blocking.
This facilitates e.g. the implementation of a zone
interlocking scheme.
Current in % In
t=k
400
300
200
NominalThreshold
100
0
1
2
3
4
5
6
Short-term increases in load following energization
Time (s)
Logic selectivity
Via two independent binary inputs the time delays
of the second and third overcurrent stages of the
phase and earth can be replaced externally by
the time delays of the logic selectivity. This takes
place via individual selection as to which of the
time stages shall be replaced with the presence
of the external signal. This facilitates e.g. a
reduction in grading time of the radial feeder or
the implementation of a zone interlocking
scheme without the application of blocking logic.
Protection Relays MiCOM P122C
06
Setting group selection
Function keys
The protection settings can be stored in two
independent groups for adaptation to various
operating or system management conditions.
Four function keys are available on the P122C
relay. Function keys F1 or F2 automatically
access the operating data or fault records
respectively.
Function keys F3 and F4 are user configurable
and can be integrated into the trip command or
can be configured to an output relay to facilitate
control access e.g. manual operation of the circuit
breaker.
Trip circuit supervision
The trip circuit supervision further increases the
operational security. The trip circuit supervision
recognizes the interruption of the trip circuit
irrespective of whether the circuit breaker is open
(OFF) or closed (ON).
Circuit breaker supervision
The preventative CB maintenance is provided by
monitoring the breaking current accumulated over
the service duration, the number of trip operations
as well as by controlling the operating times.
By reaching or exceeding the settable threshold
value an appropriate signal is issued by this
function.
Broken conductor / CT circuit
supervision
The P122C includes facilities for monitoring the
phase currents. Phase current monitoring is
based on the principle of a maximum permissible
ratio of the negative- and positive- sequence
current components to detect broken conductor
conditions.
The function can be configured for phase current
monitoring on a two-phase CT connection. This is
based on the principle of a maximum permissible
difference between the magnitudes of phase
currents IA and IC.
Event records
the last 75 events are stored in a non-volatile
memory with a 1ms resolution. Data recorded
includes the state change of binary inputs and
outputs, operating and alarm signals and any
setting changes.
Fault records
the P122C logs the last 5 faults that generated a
trip. Each log includes the following data:
•
•
•
•
Date and time
Active setting group
Alarm signal that caused the trip
Numerical fault data
Disturbance records
the internal disturbance recorder records the
sampled values of the analog variables and relevant
alarm signals. A total of 8 records each lasting up to
max. of 3 seconds can be stored and read via the
PC or optional communication interface.
Latching of the output relays (86)
All freely configurable output relays can be set to
a latched operating mode. In addition, individual
trip functions can be separately latched for the trip
output relay.
Proven protection, flush- or surfacemounted case, comprehensive local
control, just one setting file.
Disturbance record
Protection Relays MiCOM P122C
07
Information interfaces
Mechanical design
information exchange is done via the local
control panel, the PC interface and the optional
communication interface.
The communication interface (IEC 60870-5103 or Modbus) is intended for integration with
substation control systems.
the P122C consists of an aluminum case with
reversible connector blocks and adjustable
side brackets and can be used for wall surface
or panel flush mounting. In either case the
wiring connection is accomplished using screw
terminals.
Information interfaces
HMI:
Full access to settings,
signals, measurands
and function keys
PC Interface:
Local access by
protection engineer
Optional Communication Interface:
SCADA/Substation control interface
Protection Relays MiCOM P122C
08
Device Track Record
• PS 431: First non-directional time overcurrent device in compact case
design, more than 20 000 devices
since 1992.
Schneider Electric
35, rue Joseph Monier
CS 30323
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
EnergyAutomation-DS-P122C-0831-EN
As standards, specifications and designs change from time to time, please ask for confirmation
of the information given in this publication.
This document has been printed
on ecological paper
Publishing: Schneider Electric
Design: Schneider Electric
Printing:
10-2010
© 2010 Schneider Electric - All rights reserved
• MiCOM P122C: MiCOM non-directional
time-overcurrent device in compact
case design with extended functionality,
launched in 2003.