PCS-994 Frequency & Voltage Controller-NR Electric Co. Ltd

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PCS-994 is a frequency-voltage controller, which performs control functions for under-frequency, under-voltage, over-frequency and over-voltage. It can be used to perform load shedding in case of under-frequency or under-voltage conditions. It can also execute hydro-generator self-starting in a under-frequency scenario. Furthermore, it can conduct generator shut-down in case of over-frequency and system-separating in case of over-frequency or over-voltage conditions. The controller performs calculations and analysis based on the system’s voltage. Under-frequency load shedding and under-voltage load shedding provide 8 stages respectively, over-frequency provides 5 stages, and over-voltage provides 3 stages. The output of each stage can be configured via the output matrix. This relay has a total of 30 groups of outputs; each group can be configured for load shedding or generator shut-down independently.
The PCS-994 controller adopts the advanced multi-processor platform, supporting IEC 61850-8-1 MMS. In addition, RJ-45 faceplate port for testing and setting to make commissioning and maintenance easier.

Protection & Control Monitoring and Measurement Сommunication User Interface

Under-frequency load shedding function

It serves in case of frequency decrease due to lack of active power in a power system. This relay will automatically shed some loads according to the frequency decrease value, so that the generation and loads regain equilibrium. The under-frequency load shedding function provides 8 stages, which include 5 basic stages and 3 special stages.

Accelerated under-frequency load shedding function

In the case of serious lack of generation, this relay will accelerate load shedding according to df/dt, so that stage 2 and/or 3 can be accelerated to operate after stage 1 to promptly stop frequency decrease as soon as possible.

Over-frequency protection function

In case of frequency increase due to surplus active power in the power system, this relay will automatically shut down some generators according to the frequency increase value, so that the system’s frequency can be restored to normal levels. Over-frequency generator shut down function provides 5 stages.

Under-voltage load shedding function

In case of voltage decrease due to lack of reactive power in the power system, this relay will automatically shed some loads according to the voltage decrease value, so that system’s voltage is restored to normal levels. Under-voltage load shedding function provides 8 stages including 5 basic stages and 3 special stages.

Accelerated under-voltage load shedding function

In case of accelerated decrease in system voltage, this relay has the capability to accelerate load shedding according to dU/dt, so as to stop the system voltage decrease as early as possible. Thus, avoid voltage collapse, and restore voltage to optimal operating range.

Over-voltage protection function

In case of a voltage increase due to rising reactive power in the power system, this relay will automatically divide the system, so that system voltage can be restored to normal levels. The over-voltage protection function provides 3 stages.

df/dt and du/dt blocking functions

They are used to prevent possible undesired operations due to short circuit, load feedback, or abnormal frequency or voltage. Additional, blocking functions against VT circuit failure are also provided.

VT circuit supervision (VTS)
Self diagnostic
Event recorder including1024 change-of-binary-input events, 1024 supervision events and 1024 operating logs
Disturbance recorder including 32disturbance records with waveforms (The format of disturbance recorder is compatible with COMTRADE.)

Up to 4 10Base-T/100Base-TX copper Ethernet ports using IEC 61850 protocol, DNP3.0 protocol or IEC 60870-5-103 protocol over TCP/IP
Up to 2 100Base-FX optical Ethernet ports using IEC 61850 protocol, DNP3.0 protocol or IEC 60870-5-103 protocol over TCP/IP ( Sharing with 2 copper Ethernet ports)
2 RS-485 serial ports using IEC 60870-5-103 protocol
1 RS-485 serial port for clock synchronization