The PCS-924 numerical relay provides current differential protection, sum
overcurrent protection and feeder end fault protection for the T-zone in
breaker-and-a-half arrangement and ring breaker arrangement. It integrates the
three groups of CT input and provides both 3-terminal and 2-terminal current
differential protections for T-zone according to the binary input of feeder
breaker auxiliary contact. The feeder end fault protection based on the feeder
CT is adopted to avoid the trip of local breakers and send transfer trip command
to the remote end when the feeder isolator is open. In addition, the overcurrent
protection based on the sum of two breaker CTs is used as the feeder backup
protection or energizing protection.
The PCS-924 relay employs the programmable logic, configurable I/O and
definable 3-color LEDs to provide the flexibility for the specific
application.Frequency tracking is used to minimize the sampling error due to
system frequency fluctuation. The PCS-924 relay adopts the advanced UAPC
multi-processor platform which is fully complied with IEC 61850. It provides the
interfaces for station bus and process bus respectively and supports IEC
61850-8-1 MMS, GOOSE, IEC 61850-9-2 Sampling Value. And it provides the RJ-45
faceplate port for testing and setting to make commissioning and maintenance
Protection and Control
Current differential protection (87S)
3-terminal and 2-terminal current
differential protection can be automatically switched according to the binary
input of feeder isolator status. If the feeder is open by the isolator, the
feeder CT will automatically quit from the current differential protection.
Feeder end fault protection (50FLE)
This element will be valid when the
feeder isolator is open. Due to the fault between isolator and feeder CT, the
fault current only flows through the feeder CT and no fault current passes the
two breaker CTs. Thus the relay will send the transfer trip command to the
remote end and keep the local breakers closed.
Sum overcurrent protection (50P)
The overcurrent protection adopts the
sum of phase currents from two breaker CTs. It can be used as the energizing
protection or feeder backup protection.
Current drift auto adjustment
The relay continually and automatically
traces the current drifts and adjusts the zero point.
Frequency tracking is provided to accommodate the
frequency shift in power system.
Monitoring and Measurement
CT circuit supervision (CTS)
Auxiliary power supervision
Event recorder including 1024 disturbance records, 1024 binary events, 1024
supervision events and 1024 operating logs.
Disturbance recorder including 64 disturbance records with waveforms (The
file format of disturbance recorder is compatible with international COMTRADE
Counter of circuit breaker operation (single-pole tripping, three-pole
tripping and reclosing).
Two 10Base-T/100Base-TX (RJ45) ports and two optional 100Base-FX ports with
IEC 61850-8-1 MMS and GOOSE for non-time-critical message, IEC 60870-5-103 over
TCP/IP or DNP 3.0
Two RS-485 rear ports with IEC 60870-5-103
Six or Eight 100Base-FX ports with IEC 61850-9-2 Sampling Value and GOOSE
for time-critical message
One RS-485 rear port for clock synchronization
One RS-232 rear port for printer
One faceplate RJ45 port for testing and setting
Clock synchronization via Pulse-Per-Second, IRIG-B and
The relay is designed based on NR’s well established and proven UAPC
hardware platform with multi-processor architecture. The multi CPU technology
supports parallel operating simultaneously.
The two independent data acquisition paths can prevent any undesired trip
caused by component failure. One works as a fault detector and the other is
designed for protection and its logic. Tripping outputs are supervised by the
fault detector to prevent a mal-operation.
The fault detector element consists of the pickup of differential current
and the pickup of the sum current from two breaker CTs.
The differential current is monitored continuously. If the differential
current exists for a long time, an alarm will be issued to awake the
The connector type is optional, one is the plug in/out terminal connector
and the other is the screw terminal connector. The unique plug in/out terminal
connectors are used to connect the rear panel to the terminal blocks on the rack
or cabinet, making on-site commissioning and replacement much easier than using
traditional screw terminals.
The relay is compatible with IEC 61850-8-1 MMS, GOOSE and IEC 61850-9-2
Sampling Value and provides the independent interfaces for station bus and
process bus respectively.