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Tony S

Fault throwers:

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Tony S

Fault throwers:


Not strictly a transformer issue but they were an essential part of a substation/transformer protection system before the days of radio telemetry control. A fault thrower is a brutish way to trip the incoming supply.





The fault thrower provides a means of deliberately introducing a phase to earth fault in order to ensure remote end tripping of a circuit breaker, assuming pilot wires are not available for inter-tripping. The need to operate the remote circuit breaker can be due to equipment faults, such as thermal protection or low level fault currents that cannot be detected by the remote protection.


A typical application is with transformer feeders to enable the remote feeder breaker to respond to the transformer local fault detecting relays, such as Buchholz protection, local earth fault protection, etc.



As you can see the thrower is a normal breaker but only equipped for a single phase.





While at the EMEB training college the lecturer described the aftermath of someone “borrowing” the substation earth tapes just at the moment the fault thrower operated.

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