PCS-9671 Transformer Differential Relay

The PCS-9671 is a microprocessor-based relay designed for the protection of two-winding or three-winding power transformers with maximum three CT inputs. It also can be used to protect reactors or applied as an stub differential protection......

  • Overview
  • Functions
  • Features

The PCS-9671 is a microprocessor-based relay designed for the protection of two-winding or three-winding power transformers with maximum three CT inputs. It also can be used to protect reactors or applied as an stub differential protection. The restraint current differential protection, unrestraint differential protection and restricted earth fault protection are provided. The relay is capable of sampling the analog signals from conventional transformers, or receiving the sampled values from electronic CTs/VTs via merging units. The programmable logic, LEDs, binary inputs and outputs can be configured according to the specific requirements through software tool. 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.

Protection and Control
  • Restraint current differential protection. (87T) Two stages with low-setting and high-setting are provided for this protection. And the low-setting stage could be blocked by CT saturation, inrush current, overexcitation and CT circuit failure. As well the high-setting stage could be blocked by inrush current and CT circuit failure.
  • Unrestraint current differential protection. (50/87UT) It is used to clear the serious internal fault quickly.
  • Restricted earth fault protection. (REF) Up to 3 REF protections based on zero-sequence current differential element are provided.
  • Phase overcurrent protection for each side.(50/51P) Up to 3 overcurrent protections are provided.
  • Mechanical protection. (MT) Up to 8 mechanical channels are provided.
  • CT circuit supervision. (CTS) CT circuit supervision consists of two elements: CT circuit abnormality without fault detector pickup and CT circuit failure with fault detector pickup.
  • Inrush current blocking by 2nd harmonic. Phase-segregated blocking, cross blocking and composited blocking are provided for selection.
  • Overexcitation blocking by 5th harmonic. Overexcitation is detected via the ratio of 5th harmonic current and fundamental current.
  • CT saturation detection CT saturation is distinguished via composited 2nd and 3rd harmonics.
    • 64 protection operation reports, 1024 supervision alarm records, 1024 control operation records and 1024 user operation records.
    • 64 Fault and disturbance records.
    • 1024 latest SOE records, latest records of the following elements state changing.
    • Up to four 10Base-T/100Base-TX (RJ45) ports or two 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
    • Up to Six 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
    • 1 faceplate RJ45 port for testing and setting
    • Clock synchronization via pulse, IRIG-B and SNTP

    Auxiliary Testing Functions
    • Virtual tripping report generation and communication testing
    • Virtual self-supervision report generation and communication testing.
    • Virtual binary input state change report generation and communication testing.
    • Binary output testing.
    • Manual triggering fault recording.

  • This device is designed based on 32-bit high performance dual-core processor, internal high speed bus and intelligent I/O ports. The hardware adopts module design and can be configured flexibly.
  • The unique hardware design with two independent data acquisition paths can prevent the maloperation due to the hardware component failure. It will significantly enhance the reliability.
  • This device can sample the analog values from conventional transformers, or receive the sampled values from electronic CT/VT. It supports IEC60044-8, IEC61850-9-2 and GOOSE.
  • Various methods of GPS time synchronization are supported in this relay, including SNTP, IEEE1588 (V2), pulse per second (PPS) and IRIG-B synchronization.
  • The device can communicate with SAS or RTU via different communication intermediates: Ethernet network, RS-485 serial ports. The communication protocol of this device is optional: IEC61850, IEC60870-5-103 or DNP3.0.
  • Complete event recording function is provided: 64 latest protection operation reports, 1024 latest supervision, 1024 latest control operation records, 1024 latest user operation records and 1024 latest records of time tagged sequence of event (SOE) can be recorded.
  • Powerful fault and disturbance recording function is supported: 64 latest fault or disturbance waves, the duration of a wave recording is configurable.
  • Wye→Delta transfer method is used to compensate phase angle of secondary current, and correction coefficients are adopted to complete amplitude compensation.
  • Vector group of each side transformer is settable, and 24 vector groups available for two-winding transformer, and 288 vector groups available for 3-winding transformer.
  • Unrestraint instantaneous differential protection does not be blocked by any condition to ensure fast tripping in case of serious faults inside transformer.
  • Three slopes biased differential protection is adopted to avoid mal-operation caused by unbalance current during external fault.
  • 2nd , 3rd and 5th harmonic blocking function for biased differential protection is available. 2nd harmonic and 3rd harmonic is selectable to identify inrush current, and 5th harmonic is used to detect overexcitation condition. Besides, phase segregated blocking mode or crossing blocking mode is selectable.
  • CT transient detection element based on the ratio of residual current to positive current is adopted to eliminate the influence on REF due to the CT transient characteristic difference.