Under-voltage protection relay PCS-985B/AW

under-frequencyover-excitationvoltage

Product overview
PCS-985 generator-transformer unit protection can be applied for turbo-dynamo, gas-turbine, hydro, pumped storage and nuclear power generator with different connection modes. It supports conventional CT/VT and ECT/EVT, and provides interfaces for power plant automation.
For medium to large generator, two sets of PCS-985 protections can be used to achieve duplicated protection configuration. Two PCS-985 protections use different CT groups, and main and backup protection in one PCS-985 share one group of CTs.
PCS-985B provides complete protection scheme for a turbo-dynamo or nuclear power generator-transformer unit which usually comprises generator, main transformer, step-down transformer and exciter or excitation transformer.
PCS-985AW can be applied for large-scale hydro or pumped storage generator-transformer unit with different connection modes.

Current Differential Protection (tab)

• Current differential protection of generator-transformer unit (87GT)
• Current differential protection of generator (87G)
• Current differential protection of main transformer (87T)
• Current differential protection of step-down transformer (87T)
• Current differential protection of excitation transformer or exciter (87E)

Generator protection (tab)

• Phase segregated transverse differential protection (87STG)
• Incomplete current differential protection (87IG)
• High sensitive neutral point transverse differential protection (87NTG)
• Generator inter-turn protection (59NIT)
• Phase-to-phase impedance protection (21)
• Voltage controlled overcurrent protection (50/51P)
• Fundamental zero-sequence voltage stator ground fault protection (64S1)
• Generator 3rd harmonic stator ground fault protection (64S2)
• Generator stator ground fault protection with 20Hz voltage injection (64SInj)
• Generator Ping-Pang type rotor ground fault protection (64R)
• Rotor ground fault protection with low-frequency square-wave voltage injection (64RInj)
• Stator overload protection (49S)
• Excitation winding overload protection (49E)
• Generator inadvertent energization protection (50/27)
• Generator out-of-step protection (78)
• Generator reverse power protection (32R)
• Low forward power protection (32F)
• Generator shaft overcurrent protection (51GS)
• Overexcitation protection (24)
• Loss-of-excitation protection (40G)
• Overvoltage protection (59)
• Undervoltage protection (27)
• Underfrequency protection (81U)
• Overfrequency protection (81O)
• Negative-sequence overload protection (46G)
• Generator startup and shutdown protection (StShut)
• Breaker failure protection (50BF)
• Voltage balance protection (60)

Main transformer protection

• Transformer restricted earth fault protection (64REF)
• Phase overcurrent protection of HV side (50/51P)
• Phase-to-phase impedance protection of HV side (21)
• Ground overcurrent protection of HV side (50/51G)
• Gap zero-sequence overvoltage/overcurrent protection of HV side
• Overexcitation protection (24)
• Pole discrepancy protection of HV side (62PD)
• Breaker flashover protection (50F)
• Zero-sequence voltage alarm of LV side (59G)
• Overload alarm
• Initiating cooling

Step-down transformer protection

• Overcurrent protection (50/51P)
• Overcurrent protection includes two stages used as backup protection

Excitation transformer / Exciter protection

• Voltage controlled overcurrent protection of HV side (50/51P)
• Voltage controlled overcurrent protection of two branches of LV side (50/51P)
• Residual overcurrent protection of two branches of LV side (50/51G)
• Overload alarm
• Initiating cooling

Miscellaneous functions

• Mechanical protection (MR)
• Fault detector (FR)
• Voltage and current drift auto adjustment
• VT circuit supervision (VTS)
• CT circuit supervision (CTS)
• Self diagnostic
• GPS clock synchronization
• Fault recorder
• IEC61850 MMS & GOOSE for station bus
• IEC60870-5-103 protocol
• MODBUS protocol

Technical specifications

• Applicable generator types: turbo-dynamo, gas-turbine, hydro, pumped storage, nuclear
• Complete protection scheme for generator-transformer units including generator, main transformer, step-down transformer and exciter/excitation transformer
• Supports conventional CT/VT and ECT/EVT
• Provides interfaces for power plant automation
• Duplicated protection configuration possible for medium to large generators using two PCS-985 units with different CT groups
• Protection functions include differential protections (87GT/87G/87T/87E), multiple generator and transformer protections, rotor/stator ground fault schemes and frequency/voltage protections
• Communications: IEC61850 MMS & GOOSE, IEC60870-5-103, MODBUS
• Built-in fault recorder and GPS clock synchronization
• Supervision and self-diagnostic features: VTS, CTS, voltage/current drift auto adjustment, self diagnostic
• Mechanical and fault detection features: MR, FR
• Cooling and overload management: overload alarm, initiating cooling