Product/Technical Services

Line Differential Protection for Direct Fibre Pilot Wire Application GRL150

Product Overview

GRL150 provides fully numerical phase-segregated line differential protection for use with short overhead lines or cable circuits. Communication with the remote terminal is either by pilot wire or direct fibre optic link. In the case of pilot wire communication, GRL150 can be connected to new or existing pilots up to 8km in length, either directly via in-built 5kV isolation, or using optional external 20kV isolating transformers. Direct fibre optic communication can be applied to circuits up to 20km in length.

For enhanced security of the differential protection, GRL150 provides an integrated overcurrent guard scheme, magnetising inrush detection and communication channel monitoring. There is also a comprehensive range of back-up protection functions, as well as standard GR-series features such as metering, data recording and communications for remote setting and data retrieval.

Technical Description

Protection functions

  1. Applicable to overhead line and cable circuits with fibre optic or pilot wire communication

  2. Phase-segregated differential protection

  3. Integrated overcurrent guard scheme

  4. Direct intertripping

  5. Programmable logic control function

  6. Communication channel monitoring

  7. Built-in 5kV and optional 20kV isolation transformer for pilot wire communication

  8. Four stage overcurrent protection for phase and earth faults with IDMTL or DTL.

  9. Four stage sensitive earth fault protection with IDMTL or DTL (option)

  10. Inrush current detector for blocking differential and/or overcurrent trip at energisation

  11. Programmable reset characteristics.

  12. Undercurrent protection with DTL.

  13. Thermal overload protection.

  14. Broken conductor detection.

  15. Circuit breaker fail protection.

  16. Cold load pick-up feature.


Metering and recording functions

  1. Metering
    - Local and remote power system currents
    - Differential currents

  2. Recording
    - Event record
    - Fault record
    - Disturbance record

  3. Calendar and Time
    - IRIG-B port for external clock

Menu-driven human interfaces

  1. Liquid Crystal Display (LCD) display with operation keys
    - Relay setting and data display

  2. Personal computer (PC) interface
    - Relay setting
    - Recorded data display
    - Waveform analyzing

Automatic supervision

  1. Automatic monitor

  2. CT supervision.

  3. Protection signalling channel monitoring

  4. Circuit breaker condition monitoring.

  5. Trip circuit supervision.