Fault Thrower - Single phase to earth fault making switch

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

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Fault Thrower - Single phase to earth fault making switch


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.

The unit is based on the design of the Horizon circuit breaker and uses a single phase vacuum interrupter driven by a magnetic actuator for fault initiation. The switch is housed in an aluminium tank, dielectric insulation is provided by SF6 gas.

Connection to the system is achieved by either a separable connector or open terminal bushing. Manual release of the switch is available within the control cubicle housed under the tank. The fault is ‘thrown’ through the aluminium tank, two earth points are provided for safely earthing of the equipment steel work and to provide a fault path.

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