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  • PCS-978 Transformer Relay

  • PCS-978 provides full scheme protection and control solution for varies type power transformers including multiple-winding transformers and auto-transformers, as well as shunt reactors. It integrates up to 36 current/voltage inputs in order to be suitable for applications like one-and-a-half breaker or ring breaker arrangements. Up to 6 group CT inputs are included in current differential protection. In addition, 288 vector groups are available for 3-winding transformers, as well as 24 vector groups, which available for 2-winding transformer.

    The unique current differential protection includes conventional phase current differential elements and innovative DPFC differential elements, in effort to provide reliable and secure protection and to ensure the safety of vital assets. To improve the reliability of mechanical protection, dedicated high-threshold binary inputs are designed for mechanical protection. In addition, automatic CT ratio compensation and vector group compensation are provided to eliminate the external interposing CTs.

    The PCS-978 is compatible with IEC 61850 station bus and process bus applications. It supports IEC 61850-8-1 MMS, GOOSE and IEC 61850-9-2 Sampled Value. Additionally, a RJ- 45 faceplate port is provided for testing and setting in order to make commissioning and maintenance easier.

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Protection and Control
  • Transformer biased current differential protection (87T)
  • Transformer unrestrained instantaneous current differential protection (87T)
  • Transformer biased DPFC current differential protection (87T)
  • Reactor biased current differential protection (87R)
  • Reactor unrestrained instantaneous current differential protection (87R)
  • Reactor biased DPFC current differential protection (87R)
  • Inrush blocking
  • CT saturation blocking
  • Overexcitation blocking
  • CT circuit failure blocking
  • Amplitude compensation
  • Phase angle compensation
  • Restricted Earth Fault Protection (64REF)
  • Winding differential protection (87W)
  • Inter-turn fault protection for reactor (21IT)
  • Overexcitation protection (24)
  • Underfrequency and overfrequency protection (81U/81O)
  • Mechanical protection (MR)
  • Temperature protection (26)
  • Two-stage phase-to-phase impedance protection (21P)
  • Two-stage phase-to-ground impedance protection (21G)
  • Power swing blocking releasing (PSBR)
  • Four-stage phase overcurrent protection (50/51P)
  • Four-stage neutral overcurrent protection for each side(50/51G)
  • Two-stage negative-sequence overcurrent protection (50/51Q)
  • Two-stage phase overvoltage protection (59P)
  • Two-stage residual overvoltage protection (59G)
  • Four-stage undervoltage protection (27P)
  • Thermal protection (49)
  • Breaker failure protection (50BF)
  • Pole disagreement protection (62PD)
  • Phase overcurrent alarm (51PAlm)
  • Residual overvoltage alarm (59GAlm)
  • Voltage and current drift auto adjustment
  • Frequency tracking

Monitoring and Metering
  • CT failure supervision
  • VT failure supervision
  • Self diagnostic
  • Event recorder including 1024 change-of-binary-input events, 1024 supervision events and 1024 device logs
  • Disturbance recorder including 32 disturbance records with waveforms (The format is compatible with COMTRADE.)
  • Clock synchronization using IRIG-B, SNTP, PPS (Pulse-Per- Second), PPM (Pulse-Per-Minute) and IEEE 1588

Communications
  • Optional two or four 10Base-T/100Base-TX copper Ethernet ports using IEC 61850, DNP3.0 or IEC 60870-5-103 over TCP/IP
  • Optional two 100Base-FX optical Ethernet ports using IEC 61850, DNP3.0 or IEC 60870-5-103 over TCP/IP ( Sharing two copper Ethernet ports)
  • Optional two RS-485 serial ports using IEC 60870-5-103
  • One RS-485 serial port for clock synchronization
  • One RS-232 rear port for printer
  • One faceplate RJ45 port for testing and setting
  • Optional Sampling value and GOOSE communication module with six optical Ethernet ports using IEC 61850-9-2 and IEC 61850-8-1 GOOSE
  • CT transient detection element based on the ratio of zero-sequence current to positive-sequence current is provided for REF to eliminate the influence of CT transient characteristic difference.
  • The PCS-978 provides RTD input module and DC mA input module to detect the oil-temperature.
  • Maximum six groups of CT inputs for differential protection are provided.
  • 24 vector groups are available for the application to twowinding transformer.
  • 288 vector groups are available for the application to 3-winding transformer.
  • Optional inrush current distinguished principle is provided: harmonic criterion (second harmonic and third harmonic) or waveform distortion.
  • There are two optional modes for harmonic criterion: self-adaptive blocking mode and phase-to-phase cross blocking mode. Self-adaptive blocking mode can prevent maloperation during transformer energization effectively and ensure high speed for internal faults under normal operation.
  • Fifth harmonic or third harmonic criterion applied to detect overexciation condition.
  • The Δ→Y vector group compensation is used to adjust the phase angle of secondary current and the inrush current feature is reserved in each phase to realize phasesegregated inrush current restraint for percentage differential protection.
  • The DPFC restraint current differential protection is immune to load current but sensitive to small internal fault current within the transformer.
  • The restraint current differential protection with initial restraint slope consists of sensitive and conventional differential elements as well as independent CT saturation criterion.
  • Maximum 4 group CT and 1 neutral CT inputs for REF protection are provided.
  • The CT saturation detection function based on 2nd and 3rd harmonics is adopted to avoid maloperation.
  • The amplitude of residual voltage is compensated to ensure that the zero-sequence power directional element can distinguish the direction correctly when system impedance is too small.
  • Voltage for overexcitation protection calculation is the RMS value of three phase voltages which is not affected by frequency fluctuation.
  • Directional element can be selected to control each stage phase overcurrent protection with three options: none direction, forward direction and reverse direction.
  • Disturbance records are composed of 64 fault reports and 64 disturbance waveforms. The file format of waveform is compatible with international COMTRADE91 and COMTRADE99 file. Up to 80 analog inputs and 200 binary inputs can be recorded, and three oscillograph triggering mode are supported.
  • 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.