PCS 902s x datasheet EN overseas general x r1 00

About This Document
About This Document
The manual describes the control, protection, measurement and supervision functions with the
information of relevant hardware for PCS-902S Line Distance Relay.

Copyright © 2019 NR. All rights reserved.
NR, the NR logo are either registered trademarks or trademarks of NR Electric Co., Ltd. No NR
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The information in this document is provided for informational use only and does not constitute a legal
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is subject to change without prior notice.
To the extent required the products described herein meet applicable IEC and IEEE standards, but no
such assurance is given with respect to local codes and ordinances because they vary greatly.
Although every reasonable effort is made to present current and accurate information, this document
does not purport to cover all details or variations in equipment nor provide for every possible contingency
to be met in connection with installation, operation, or maintenance. Should further information be
desired or should particular problems arise which are not covered sufficiently for your purposes, please
do not hesitate to contact us.

PCS-902S Line Distance Relay

1

Document Revision History
Document Revision History
PN: ZL_PCS-902S_X_DataSheet_EN_Overseas General_X
Current version: R1.00
Corresponding Version
Release Date

2

Document

Software

R1.00

R1.00

2019-01-31

Description of change



Form the original manual.

PCS-902S Line Distance Relay

Overview
Overview

PCS-902S is a high-speed transmission line distance relay featuring single-pole and three-pole tripping
and reclosing with synchronism check, which can protect overhead and underground lines, feeders and
cables on all voltage levels with highest selectivity possible. The large number of protective and
automatic functions available permits their utilization in all areas of line protection. The devices contain
control, measurement and monitoring functions. The large number of communication interfaces and
communication protocols satisfies the requirements of communication-based selective protection and of
automated operation. Their modular structure permits line protection devices always to be adapted
flexibly to the individual requirements.

PCS-902S Line Distance Relay

3


Highlights
Highlights


Unified software and hardware platform, comprehensive power grid solutions of protection, control,
measurement and monitoring, easy to use and maintain.



High reliability and redundancy design for drive systems of the sampling circuit and the output circuit
ensure that overall reliability of the device is high. Real-time sampling based on dual AD can mutually
check and detect the potential abnormality in the sampling circuit in time. The control power supply of
the output relay is independent with the control circuit of trigger signals, which can prevent from

undesired operation caused by the abnormality of drive circuit of output relays.



Various function modules can satisfy various situations according to the different requirements of
users. Flexible and universal logic programming, user-defined configuration of BI/BOs, buttons and
LEDs and powerful analog programming are supported.



Modularized hardware design makes the device be easily upgraded or repaired by a qualified service
person. It can be mixed with different I/O modules, with online self-check and monitoring function,
and the device can be restored from abnormal operation only need to replace a single abnormal
module.



Support memory check and error correction function, ensure high reliability and safety.



Support the internet communication protocol of native PRP/HSR and RSTP.



Fully compatible with IEC 61850 edition 1 & edition 2, support MMS service, IEC 62351
communication service, GOOSE communication in station level & process level, SV communication
with multi-sampling rate.



Full comply with cyber security standards, including IEC62443, IEC62351, IEEE1686, NERC-CIP,
support role based access control (RBAC), security audit, security encryption communication and
security tool, improve the cyber security capability of devices.



Powerful COMTRADE fault and disturbance recording function is supported. The whole recording
time is automatically configurable by the fault duration, which is convenient to fault analysis and
replay. The recording sample rate is up to 9.6kHz.



Settable secondary rated current (1A/5A) and settable voltage threshold of binary input



Support small size and large size LCD, control and multifunction button



Support flush mounting, semi-flush mounting, surface mounting, wall mounting and other mounting
methods.



Cross screw IO, CT/VT terminals can support AWG12 specification connector and 4mm2 lead



Multiple variants with case size 1/1 or 1/2 × 19"



Protection class of front side is up to IP54

4

PCS-902S Line Distance Relay


Highlights


PCS-Studio is the application software on the user's PC for the interface with PCS S series devices
providing all the related functionality. It ranges from device configuration to full substation design of
bay integration.



Support IEEE1588, IRIG-B clock synchronization



Support actual system phase sequence, either ABC or ACB, incorrect connection of actual phase
sequence can automatically be verified and relevant protection functions can be blocked.



Equipped with high-speed large capacity output relay, its operation speed is less than 1ms and its

break capacity is up to 10A. The real-time supervision for output drive circuit can detect the
abnormality in advance.



Support setup up to 40 users and allow each user to own different password and access authority.

PCS-902S Line Distance Relay

5


Features
Features


Two-terminal transmission line application, including overhead line and cable



Distance Protection


Distance protection adopted the half-wave algorithm is also supported, and its typical operation
time is 12-15ms.



6 zones distance protection, independent zero-sequence compensation factor for each zone,
the phase-to-ground and phase-to-phase characteristic of distance protection can be set

independently.



The unique power swing blocking releasing logic and can properly supervise distance protection
during power swing, which ensures distance protection to operate correctly for internal faults

Unique phase selector has the same protection zone as operation element. The phase selection is
automatically resulted according to the reliability of phase selector, so that to avoid probable
mistaken multi-phase selection by adopting overreaching phase selector.



Special overcurrent element of breaker failure protection, its dropoff time is no more than 15ms.



The overcurrent protection is combined with harmonic blocking and cold load starting logic, which
can prevent from mal-operation affected by impulse current while the transformer is initiated on
no-load.



Selectable IEC, ANSI inverse-time characteristic curves, also the curve can be defined by users and
the inverse-time dropoff curve selection is supported.



Support single-ended impedance-based fault location, mutual compensation for parallel lines
arrangement is also available.



Both dedicated fiber channel and multiplexing fiber channel are supported, and single mode and
multi-mode channel combination operation mode is enable. Communication rate supports 64kbit/s
and 2Mbit/s, and communication protocol supports C37.94 and G.703.

6

PCS-902S Line Distance Relay

Transmission



Line

during power swing, and prevents distance protection from mal-operation during power swing.


Functions Overview
Functions Overview
3VT

Busbar

52

21

67P

67G

67Q

21D

50/51P

50/51G

50/51Q

32R

50DZ

46BC

62PD

50BF

FR

59P

37

FL

59Q

SOTF

59G

81O

27P

81U

81R

*

3CT

85

Data transmit/Receive

1VT
25

79

Line

Protection Functions
ANSI

Protection functions

Remark


Independent pilot zone (forward direction and reverse
direction, mho or quadrilateral characteristics)

Pilot distance protection

85



PUTT, POTT, Blocking, Unblocking, Zone Extension



Current reversal logic



Weak infeed echo or echo&trip



Open breaker echo



Directional zero-sequence comparison element for pilot
scheme

Pilot directional earth-fault protection

21

Distance protection



PTT, Blocking and Unblocking



Current reversal logic



Weak infeed echo or echo&trip



Open breaker echo



Up to 6 zones



3 independent phase-to-ground distance elements for
each zone



3 independent phase-to-phase distance elements for each
zone


PCS-902S Line Distance Relay

Selectable

quadrilateral

characteristics

or

mho
7


Functions Overview
characteristics



Independent impedance settings and time delays for each
zone



Zero-sequence current compensation for phase-to-ground
distance element



Selectable forward direction, reverse direction or non
direction (except zone 1 that is fixed as forward direction)

21D

DPFC distance protection



Load encroachment for each zone



Power swing blocking and releasing for each zone



Faulty phase selection for each zone



Fixed forward direction



High-speed operation



Supplementary for zone 1 of distance protection



Up to 6 stages with independent logic



Voltage control element for each stage



Optional direction element for each stage, including

67P
Phase overcurrent protection
50/51P

forward direction, reverse direction or non direction



Optional definite-time characteristics and inverse-time
characteristics for each stage



Trip purpose or alarm purpose for each stage



Harmonic control element for each stage



Up to 6 stages with independent logic



Optional direction element for each stage, including
forward direction, reverse direction or non direction

67G


Earth fault protection
50/51G

67Q

Optional definite-time characteristics and inverse-time
characteristics for each stage

Negative-sequence

overcurrent



Selectable trip purpose or alarm purpose for each stage



Harmonic control element for each stage



Up to 2 stages with independent logic



Optional direction element for each stage, including
forward direction, reverse direction or non direction

50/51Q

protection



Optional definite-time characteristics and inverse-time
characteristics for each stage

SOTF

59P

27P

8

Switch onto fault

Phase overvoltage protection

Phase undervoltage protection



Via distance measurement elements



Via dedicated earth fault element



Via phase overcurrent element



Up to 2 stages with independent logic



Optional definite-time characteristics and inverse-time
characteristics for each stage



Optional phase voltage or phase-to-phase voltage



Optional “1-out-of-3” logic or “3-out-of-3” logic



Selectable trip purpose or alarm purpose for each stage



Up to 2 stages with independent logic



Optional definite-time characteristics and inverse-time
PCS-902S Line Distance Relay

Functions Overview
characteristics for each stage


Optional phase voltage or phase-to-phase voltage



Optional “1-out-of-3” logic or “3-out-of-3” logic



Blocked by instantaneous VT circuit failure



Selectable trip purpose or alarm purpose for each stage



Optional auxiliary criterion, including CB position check
and current check

Negative-sequence

overvoltage

59Q
protection
59G

Residual overvoltage protection

81O

Overfrequency protection

81U

Underfrequency protection

81R

Rate of change of frequency protection

32R

Reverse power protection

37

50BF

50DZ



Up to 2 stages with independent logic



Selectable trip purpose or alarm purpose for each stage



Up to 2 stages with independent logic



Selectable trip purpose or alarm purpose for each stage



Up to 6 stages with independent logic



Voltage control element



Up to 6 stages with independent logic



Voltage control element



Up to 6 stages with independent logic



Voltage control element



Up to 2 stages with independent logic



Selectable trip purpose or alarm purpose for each stage



Optional auxiliary criterion, including CB position check
and current check

Undercurrent protection


Selectable trip purpose or alarm purpose for each stage



Phase-segregated re-trip and three-phases re-trip



Optional current criterion (phase overcurrent element,

zero-sequence overcurrent element, negative-sequence

Breaker failure protection

Dead zone protection

overcurrent element)


Optional circuit breaker position check



Two time delays



Clear the dead zone faults between CT and the circuit
breaker


62PD

Pole discrepancy protection

Initiated by three auxiliary contacts of phase-segregate
circuit breaker



Optional auxiliary criterion (zero-sequence current element
or negative-sequence current element)


46BC

Broken conductor protection

Adopt

the

ratio

of

negative-sequence

current

to

positive-sequence current (Ι2/Ι1) to detect the broken
conductor.

25

79

Synchrocheck

Auto-reclosing



Independent logic for auto-reclosing and manually closing



One shot or multi-shot



1-pole AR, 3-pole AR or 1/3-pole AR



Optional trigger mode, including protection operating and
external binary input

PCS-902S Line Distance Relay

9


Functions Overview
FL

Fault location



Support synchro-check and voltage check



Single-end fault location



Double-end fault location



Zero-sequence mutual coupling compensation for parallel
lines

DPFC is the abbreviation of deviation of power frequency component.

Control Functions


Circuit breaker & disconnector control (Remote/local)



Synchronism check for remote and manual closing



Voltage switching

Measurement functions


Energy metering (active and reactive energy are calculated in import respectively export direction)



Power (Apparent/Real/Reactive)



Power Factor



Frequency



Event Recorder including 1024 disturbance records, 1024 binary events, 1024 supervision events,
256 control logs and 1024 device logs.



Disturbance recorder including 64 disturbance records with waveforms (The file format of
disturbance recorder is compatible with international COMTRADE file.)

Supervision functions



VT circuit supervision



CT circuit supervision



Trip/Close coil supervision



Self diagnostic



Pilot communication channel supervision



DC power supply supervision



Channel status statistic



System frequency supervision

10

PCS-902S Line Distance Relay


Functions Overview
Pilot channel scheme


Optional single- or dual- pilot channels (fiber optic)



Support G.703 and C37.94

Communication functions


Up to four 10Base-T/100Base-TX copper Ethernet ports using IEC 61850, DNP3.0 or IEC
60870-5-103 over TCP/IP



Up to four 100Base-FX optical Ethernet ports using IEC 61850, DNP3.0 or IEC 60870-5-103 over
TCP/IP



Two RS-485 serial ports using IEC 60870-5-103



One RS-485 serial port for clock synchronization



Support GOOSE communication module using IEC 61850-8-1 GOOSE



Full compatibility between IEC 61850 Editions 1 and 2



Redundancy protocols PRP, HSR and RSTP



One front RJ-45 port and one rear RJ-45 port for debugging

User Interfaces


Friendly HMI interface with LCD, easy-to-use keypad aids simple navigation and set-point
adjustment



Push buttons for open/close, switch for selection between local and remote control, and user's login
and logout authority management



4 Programmable operator pushbuttons with user-configurable labels



Up to 18 programmable target LEDs with user-configurable labels



1 RS-485 rear ports for printer



Language switchover—English+ selected language



Configuration tool—PCS-Studio

Additional functions


User programmable logic



Fault location



Fault phase selection

PCS-902S Line Distance Relay

11


Functions Overview


Parallel line compensation for fault location



Switching system phase sequences function (ABC or ACB)



Clock synchronization



12



IRIG-B: IRIG-B via RS-485 differential level, TTL level or optical fibre interface



PPS: Pulse per second (PPS) via RS-485 differential level or binary input



PPM: Pulse per minute (PPM) via RS-485 differential level or binary input



IEEE1588: Clock message based on IEEE1588 via optical fibre interface



SNTP (PTP): Unicast (point-to-point) SNTP mode via Ethernet network



SNTP (BC): Broadcast SNTP mode via Ethernet network



Message (IEC103/Modbus/DNP3.0): Clock messages through IEC103 protocol, Modbus
protocol and DNP3.0 protocol

Cyber security


NERC CIP



IEC 62351



IEC 62443



IEEE 1686

PCS-902S Line Distance Relay


Typical Application
Typical Application
PCS-902S protect overhead and underground lines, feeders and cables on all voltage levels with
highest selectivity possible.
52

52

PCS-902S

Optical fibre channel or PLC channel

PCS-902S

Communication channel via direct dedicated fibre, MUX or PLC

Figure 1 Typical application of single circuit breaker
Bus1
Single-phase
voltage

52

PCS-902S

Line 1

Three-phase
voltage
52
Line 2
Single-phase
voltage

52

Bus2

Figure 0-2 Typical application of double circuit breakers

PCS-902S Line Distance Relay

13

Protection Functions
Protection Functions
Circuit Breaker Position Supervision
In order to prevent that wrong status of CB position is input into the device via binary input, appropriate
monitor method is used to check the rationality of the binary input. When the binary input of CB open
position is detected, the status of CB position will be thought as incorrect and an alarm [Alm_52b] will be
issued if there is current detected in the line.
Together with the status of circuit breaker and the information of external circuit, this function can be
used to supervise control circuit of circuit breaker.

Fault Detector (FD)
Fault detector is responsible to determine fault appearance on the protected power system. The device
will switch to protection calculation after the fault detector picks up, for example the calculation of
distance protection, and to determine the operating logic. If the fault is within the protected zone, the
device will issue tripping command. The fault detector continuously detects the change of
phase-to-phase power frequency current and the calculated zero-sequence and negative-sequence
currents. The fault detector includes:
1.

Fault detector based on DPFC current: DPFC current is greater than the setting value

2.

Fault detector based on residual current: Zero-sequence current is greater than the setting value

3.

Fault detector based on negative-sequence current: Negative-sequence current is greater than the

setting value

Optical Pilot Channel (FO)
The devices can transmit Boolean quantities such as blocking signal, permissive signal and transfer trip
signal to the remote end via optical fibre channel. Up to 2 optical fibre channels are supported, which can
be dedicated optical fibre channel or multiplex channel, the channel mode could be selected as
single-mode or multi-mode. The communication rate can be 64kbits/s or 2048kbits/s, and G.703 or
C37.94 are optional for communication protocol. 8 digital bits are integrated in each frame of
transmission message for various applications, and 8 binary signals are configurable. Each received
message frame via fibre optical channel will pass through security check to ensure the integrity of the
message consistently.

Pilot Distance Protection (85)
Pilot distance protection requires communication channel to exchange protection information at both
ends. The channel may be dedicated or multiplexed channel through optical fiber or any other
communication media. Pilot distance protection has schemes of permissive underreaching transfer trip
(PUTT), permissive overreaching transfer trip (POTT) and blocking. The device provides dual pilot
14

PCS-902S Line Distance Relay


Protection Functions
distance protections. The communication media and mode can be independent each other.
Pilot distance protection determines whether it will send the signal to the remote end according to the
discrimination result of the distance element or direction element. Pilot distance protection can be
divided into permissive scheme and blocking scheme according to whether the signal sent is used to
permit tripping or block tripping. For permissive scheme, it can be divided into overreaching mode or
underreaching mode according to the setting of distance element and scheme selected, furthermore, it
will provide the unblocking scheme as auxiliary function. For overreaching mode, current reversal logic

and weak infeed logic are available for parallel line operation and weak power source situation
respectively.

Pilot Directional Earth-fault Protection (85)
Pilot directional earth-fault protection can be used independently, for example, no distance protection is
equipped with the device but fast operation is required for the whole line, or it is used as backup
protection of pilot distance protection to enhance the sensitivity for an earth fault with high fault
resistance.
Pilot directional earth-fault protection comprises permissive scheme and blocking scheme. It can share
pilot channel 1 with pilot distance protection, or uses independent pilot channel 2. For underreach mode,
pilot directional earth-fault always adopts independent pilot channel 2. Sending permissive signal (or
terminating sending signal) to the opposite end is controlled by forward direction element. Current
reversal logic is available for parallel line operation and CB echo logic is provided once pilot directional
earth fault protection is enabled. Current reversal logic is only used for permissive scheme. For blocking
scheme, current reversal need not be considered because there is a settable time delay in pilot
directional earth-fault protection.

Distance Protection (21L)
Distance protection includes three independent phase-to-phase measuring loops as well as three
independent phase-to-ground measuring loops. Both mho and quadrilateral characteristics are available
for different application. In addition, load encroachment, power swing blocking and releasing, and faulty
phase selection functions are also provided.
Up to 8 zones distance protection are supplied, including 1 zone distance protection with fixed forward
direction, 5 zones distance protection with settable direction, 1 zone pilot distance protection with fixed
forward direction and 1 zone pilot distance protection with fixed reverse direction. Each zone includes
three independent phase-to-phase measuring loops as well as three independent phase-to-ground
measuring loops. Phase-to-ground distance element should be compensated by zero-sequence current
of local line. Zone 2~6 can select forward direction, reverse direction and non direction.
Load encroachment can distinguish effectively between heavily loaded line and faulty line, and the risk of
encroachment of the load impedance into the tripping characteristics of the distance protection can be

excluded.
Power swing blocking and releasing can prevent distance protection from undesired operation during
power swing, even if measured impedance reaches into operating area of distance protection. Moreover,
PCS-902S Line Distance Relay

15


Protection Functions
distance protection can operate reliably when a fault occurs during power swing.
Based on distance protection characteristics, faulty phase can be identified correctly. It is benefit for the
faulty phase selection which is important to the line which uses phase-segregated circuit breaker and
provides valid information for 1-pole AR and fault location.

DPFC Distance Protection (21D)
As an independent fast protection, DPFC distance protection is mainly used to clear close up fault of
long line quickly, its protected range can set as 60%~70% of the whole line. Since DPFC distance
protection only reflects fault component and is not influenced by current change due to load variation
and power swing, power swing blocking (PSB) function is not required. Moreover, there is no transient
overreaching due to infeed current from the remote power supply because it is not influenced by load
current.

Distance Switch Onto Fault Protection (21SOTF)
Distance SOTF protection shares pickup signal as initiation condition with distance protection. It is
selectable among zone 2, 3 or 4 of distance protection which is accelerated to trip by manual closing or
auto-reclosing, and they can enable or disable be controlled by power swing blocking. Distance SOTF
protection equips with independent time delay. Zone 2 of distance protection is fixedly accelerated to trip
by 1-pole AR. Zone 2 of distance protection is also accelerated to trip by pole discrepancy condition. For
single-phase fault, distance SOTF protection will accelerate to operate if another fault happens to the
healthy phase before auto-reclosing.

Phase Overcurrent Protection (50/51P)
The device can provide six stages of phase overcurrent protection with independent logic. Each stage
can be independently set as definite-time characteristics or inverse-time characteristics. The dropout
characteristics can be set as instantaneous dropout, definite-time dropout or inverse-time dropout. It can
be chosen whether it is blocked by voltage control element or harmonic control element. The direction
control element can be set as no direction, forward direction and reverse direction. Phase overcurrent
protection picks up when the current exceeds the setting, and operates after a certain time delay. Once
the fault disappears, phase overcurrent protection will dropout. Phase overcurrent protection can
operate to trip or alarm.

Phase Current SOTF Protection (50PSOTF)
Phase current SOTF protection will operate to trip three-phase circuit breaker with a time delay when
manual closing or auto-reclosing. For in-line transformer application, large inrush current generated
during manual closing and auto-reclosing will lead to an undesired operation of phase current SOTF
protection. Second harmonic blocking can be selected to prevent maloperation due to inrush current.

16

PCS-902S Line Distance Relay


Protection Functions
Earth Fault Protection (50/51G)
The device can provide six stages of earth fault protection with independent logic. Each stage can be
independently set as definite-time characteristics or inverse-time characteristics. It can be chosen
whether it is blocked by harmonic control element. The direction control element can be set as no
direction, forward direction and reverse direction. The zero-sequence current used by earth fault
protection always adopts calculated zero-sequence current. Earth fault protection can operate to trip or
alarm.

Residual Current SOTF Protection (50GSOTF)
Residual current SOTF protection will operate to trip three-phase circuit breaker with a time delay via
1-pole auto-reclosing, manual closing or 3-pole auto-reclosing. For in-line transformer application, large
inrush current generated during manual closing and auto-reclosing will lead to an undesired operation of
residual current SOTF protection. Second harmonic blocking can be selected to prevent maloperation
due to inrush current.

Negative-sequence Overcurrent Protection (50/51Q)
The device can provide two stages of negative-sequence overcurrent protection with independent logic.
Each stage can be independently set as definite-time characteristics or inverse-time characteristics. For
parallel lines or a ring network line, the flow direction of negative-sequence current may be different.
Considering the selectivity of negative-sequence overcurrent protection, the direction control element
can be set as no direction, forward direction and reverse direction. Negative-sequence overcurrent
protection can operate to trip or alarm.

Phase Overvoltage Protection (59P)
The device can provide two stages of phase overvoltage protection with independent logic. When a high
voltage occurs in the system, phase overvoltage protection will operate to isolate the fault from the
system after a time delay if the voltage is greater than the setting. In addition, phase overvoltage
protection also provides the alarm function to notify that there is the overvoltage in the system and find
the cause timely to prevent from further deterioration of the fault.
Each stage of phase overvoltage protection can be independently set as definite-time characteristics or
inverse-time characteristics. The dropout characteristics can be set as instantaneous dropout and
definite-time dropout.
Phase voltage or phase-to-phase voltage can be selected to be used by the protection calculation.
“1-out-of-3” or “3-out-of-3” logic can be selected for the protection criterion. (1-out-of-3 means any of
three phase voltages, 3-out-of-3 means all three phase voltages).

Residual Overvoltage Protection (59G)

The device can provide two stages of residual overvoltage protection with independent logic. When the
PCS-902S Line Distance Relay

17


Protection Functions
residual voltage is greater than the setting, residual overvoltage protection will operate to isolate the fault
from the system after a time delay. In addition, residual overvoltage protection also provides the alarm
function to notify that there is an earth fault leading to residual voltage generation, and find the cause
timely to prevent from further deterioration of the fault. Residual overvoltage protection supports
definite-time characteristics. The dropout characteristics can be set as instantaneous dropout and
definite-time dropout.

Negative-sequence Overvoltage Protection (59Q)
The device provides two stages of negative-sequence overvoltage protection. If negative-sequence
voltage is greater than the setting, negative-sequence overvoltage protection will operate.
Negative-sequence overvoltage protection is with independent definite-time characteristics and
definite-time or instantaneous dropout characteristics.

Phase Undervoltage Protection (27P)
The device can provide two stages of phase undervoltage protection with independent logic. When the
voltage drops in the system and it is lower than the setting, phase undervoltage protection will operate to
isolate the fault from the system after a time delay. In addition, phase undervoltage protection also
provides the alarm function to notify that there is the undervoltage in the system and find the cause
timely to prevent from further deterioration of the fault.
Each stage of phase undervoltage protection can be independently set as definite-time characteristics or
inverse-time characteristics. The dropout characteristics can be set as instantaneous dropout and
definite-time dropout.
Phase voltage or phase-to-phase voltage can be selected to be used. “1-out-of-3” or “3-out-of-3” logic

can be selected for the protection criterion. (1-out-of-3 means any of three phase voltages, 3-out-of-3
means all three phase voltages). The circuit breaker position with/without the current condition can be as
an auxiliary criterion for phase undervoltage protection.

Overfrequency Protection (81O)
The device can provide six stages of overfrequency protection. If the system frequency is greater than
the setting, overfrequency protection will operate to remove some part of active power supplies from the
system. Overfrequency protection is with independent definite-time characteristics and with
instantaneous dropout characteristics.

Underfrequency Protection (81U)
The device can provide a six stages of underfrequency protection. If the system frequency is less than
the setting, underfrequency protection will operate to shedding some part of loads from the system.
Underfrequency protection is with independent definite-time characteristics and with instantaneous
dropout characteristics.

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PCS-902S Line Distance Relay


Protection Functions
Frequency Rate-of-change Protection (81R)
The device can provide six stages of frequency rate-of-change protection. If the system frequency
rate-of-change is greater than the setting, frequency rate-of-change protection will operate. Frequency
rate-of-change protection is with independent definite-time characteristics and with instantaneous
dropout characteristics.

Reverse Power Protection (32R)
The device can provide two stages of reverse power protection. If the reverse power is detected and it is

greater than the setting, reverse power protection will operate. Reverse power protection is with
independent operating definite-time characteristics and with instantaneous dropout characteristics.
Reverse power protection can be enabled or disabled by the settings and the signals. For some specific
applications, reverse power protection needs to be blocked by the external signal, so the device provides
an input signal to be used to block reverse power protection.

Undercurrent Protection (37)
The device can provide one stage of undercurrent protection for tripping purpose or alarm purpose. For
different protected equipment, single-phase criterion or three-phase criterion can be selected. The circuit
breaker position and the load current also can be taken as the enabling conditions of undercurrent
protection. Undercurrent protection is with definite-time operating characteristics and instantaneous
dropout characteristics.

Breaker Failure Protection (50BF)
According to the tripping information from the device and the auxiliary information (the current and the
position) of target circuit breaker, breaker failure protection constitutes the criterion to discriminate
whether the target circuit fails to open. If the criterion is confirmed, breaker failure protection will operate
to trip the target circuit breaker with the re-tripping time delay, trip it again with the first time delay and trip
the adjacent circuit breakers with the second time delay. As a special backup protection, breaker failure
protection can quickly isolate the fault, reduce the affected range by the fault, keep system stability and
prevent generators, transformers and other primary equipments from seriously damaged. For breaker
failure protection, phase-segregated re-trip, three-phases re-trip and two time delays are available.

Dead Zone Protection (50DZ)
For some wiring arrangement (for example, circuit breaker is located between CT and the line), if fault
occurs between CT and circuit breaker, line protection can operate to trip circuit breaker quickly, but the
fault have not been cleared since local circuit breaker is tripped. Here dead zone protection is needed in
order to trip relevant circuit breaker.

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Protection Functions
Broken Conductor Protection (46BC)
Broken-conductor fault mainly is single-phase broken or two-phases broken, so broken conductor
protection based on the ratio of negative-sequence current to positive sequence current can detect the
broken-conductor fault. According to the ratio of negative-sequence current to positive-sequence current
(I2/I1), it is used to judge whether there is an broken-conductor fault. Negative-sequence current under
normal operating condition (i.e. unbalance current) is due to CT error and unbalance load, so the ratio of
negative-sequence current to positive-sequence current (amplitude) is relative steady. The value with
margin can then be used as the setting of broken conductor protection. It is mainly used to detect
broken-conductor fault and CT circuit failure as well.

Pole Discrepancy Protection (62PD)
The pole discrepancy of circuit breaker may occur during operation of a breaker with segregated
operating gears for the three phases. Pole discrepancy protection determines three-phase breaker pole
discrepancy condition by its phase segregated CB auxiliary contacts. In order to improve the reliability of
pole discrepancy protection, zero-sequence current element or negative-sequence current element can
be selected as auxiliary criterion.

Transfer Trip (TT)
The device provides phase-segregated transfer trip and three-phases transfer trip, which can be
controlled by local fault detector. In addition, the input signals of phase-segregated transfer trip and
three-phases transfer trip are always supervised, and the device will issue an alarm and block transfer
trip once the binary input is energized for longer than the setting value. Both phase-segregated transfer
trip and three-phases transfer can be selected to operate to block AR.

Trip Logic (TRP)

Trip logic gathers signals from phase selection and protection tripping elements and then converts the
operation signal from protection tripping elements to appropriate tripping signals. The device can
implement phase-segregated tripping or three-phase tripping, and may output the contact of blocking AR
and the contact of initiating breaker failure protection.

Automatic Reclosure (79)
AR can be used with either integrated device or external device. When AR is used with integrated device,
the internal protection logic can initiate AR, moreover, a tripping contact from external device can be
connected to the device via input signal to initiate integrated AR.
When AR is used as an independent device, it can be initiated by operating signal of protections. The
device can output some configurable output signals (such as, contact signals or digital signal, for
example, GOOSE signal) to initiate external AR or block external AR. The contact signals includes
phase-segregated tripping signal, single-phase tripping signal, three-phase tripping signal, blocking AR
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PCS-902S Line Distance Relay


Protection Functions
signal and protection operating signal, etc,. According to requirement, these contacts can be selectively
connected to external AR.
According to the requirement, the device can be set as one-shot or multi-shot AR. When adopting
multi-shot AR, the AR mode of first time reclosing can be set as 1-pole AR, 3-pole AR or 1/3-pole AR.
The rest AR mode is only 3-pole AR.

Fault Location (FL)
The device provides single-end fault location. Fault location picks up after the device operates to trip
when there is a fault in the line. If the pickup time is greater than 25ms, fault location is calculated with a
time delay of 10ms after the device operates to trip. If the pickup time is smaller than 25ms, fault location
is calculated with a time delay of 20ms after the device operates to trip.

When there is a protection tripping with faulty phase selection, the calculation of the fault impedance is
initiated. According to the fault impedance to locate the fault point, two calculation results are provided,
which is the length of the fault point distance from the end of the device and its percentage of lines
length.
For parallel lines, there is a mutual coupling between each phase, and there is also a mutual coupling
between parallel lines. The coupling strength between parallel lines associated with the transposition
way. For parallel lines with fully transposition, positive-sequence and negative-sequence mutual
coupling is very small, and usually can be ignored. But zero-sequence mutual coupling has a greater
influence on the line, so the measured impedance must consider the effect.

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Control Functions
Control Functions
Switchgear Control
A control command can realize various control signals such as the CB/DS/ES opening/closing. In order
to ensure the reliability of the control output, a locking circuit is added to each control object. The
operation is strictly in accordance with the selection, check and execution steps, to ensure that the
control operation can be safely and reliably implemented. In addition, the device has a hardware
self-checking and blocking function to prevent hardware damage from maloperation output.
When the device is in the remote control mode, the control command may be sent via the IEC
60870-5-103 or IEC 61850 protocol; when it is in the local control mode, the local operation may be
performed on the device LCD or panel handle.
A complete control process is:
1.

Protocol module sends a selection command;

2.

Control module responds the success or failure result of selection;

3. If the selection is successful, the protocol module sends an execution command, otherwise it sends
a cancel command;
4.

Control module responds the success or failure result of execution;

5.

The control operation may be open/close or up/down/stop.

When the device is in the maintenance status, it can still respond to local control commands.
The switchgear control function can cooperate with functions such as synchronism check and
interlocking criteria calculation to complete the output of the corresponding operation command. It can
realize the normal control output in one bay and the interlocking and programmable logic configuration
between bays. This device supports the following functional control module:
Module

Description

CSWI

Control of circuit breaker (CB), disconnector switch (DS) or earthing switch (ES)

RMTLOC

Remote or local control mode

XCBR

Synthesis of CB position, three-phase or phase separated

XSWI

Synthesis of DS/ES position

SXCBR/SCSWI

Trip statistics of CB/DS/ES

RSYN

Synchronism check for CB closing

CILO

Interlocking logic for CB/DS/ES control

MCSWI

Manual control of CB/DS/ES

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PCS-902S Line Distance Relay

Control Functions
The initiation of a control command may be sent to the device by the SCADA or the NCC through
protocol IEC 60870-5-103 or IEC 61850. It may also be the operation of the device LCD or the manual
triggering through configured signal. The command is sent by the CPU to the control module for
processing, and a control record is made on the CPU module according to the control result.

Manual Closing Synchronism Check
The synchronism check includes synchro-check and dead charge check. By comparing between the
reference voltage and the synchronization voltage, the synchro-check is satisfied if the voltage
difference, frequency difference, slip frequency difference and phase angle difference are all within their
setting ranges. The dead charge check mode checks only the synchro-check voltage. Several dead
charge check modes are supported, including dead synchronism voltage & dead reference voltage
check, live synchronism voltage is & dead reference voltage, synchronism voltage is dead & live
reference voltage, dead reference voltage, dead synchronism voltage, live synchronism voltage & dead
reference voltage or dead synchronism voltage & live reference voltage, dead synchronism voltage or
reference voltage.

Voltage Switching
The voltage switching function can be used to switch the reference and synchronization voltages for
double busbar and 3/2 CB arrangements. The "Near priority" principle is adopted by default, and the
user interface for programmable switching logic is also reserved.
For double busbar arrangement, selection of appropriate voltage signals from Bus 1 and Bus 2 for
synchronizing are required. Line VT signal is taken as reference to check synchronizing with the voltage
after voltage selection function.
For one and a half breakers arrangement, selection of appropriate voltage signals among Line1 VT,
Line2 VT and Bus 2 VT as reference voltage to check synchronizing with Bus 1 voltage signal for closing
breaker at Bus 1 side.

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