To safe guard against the drastic consequences of failure to clear faults rapidly, many power supply authorities install 2 independent systems of protection for major transmission lines. There remains however the possibility of the circuit breaker itself failing to operate and this hazard is traditionally covered by remote breaker back-up.; CTIG relay is a 3 phase or 2 phase and earth fault instantaneous over current unit intended for use with a time delay to give back-up protection in the event of a circuit breaker failure. A particular feature of the CTIG relay is a fast reset, which enables the time delay to be set closer to the breaker trip-time.
