Morris Line Engineering UK

Fault Throwing Switches

MLE’s proven fault throwing switches are available up to 72 kV and provide a means of deliberately introducing a fault to ensure tripping of a circuit breaker


The purpose of the type “FTS” fault throwing switch is to create a deliberate fault on an overhead line, responding from a signal given by the protective relays of a malfunctioning transformer. Tripping of the source circuit breaker which senses the fault will automatically cut off all of the system being supplied

Type ‘FTS’ Fault Throwing Switches

The switch portion is rotating double break disconnector to which has been added a closing spring toggle, which in the closed ‘straight-line’ position locks the switch closed to prevent bounce and throw open by theshort-circuit forces encountered on closing. At near ground level is positioned the spring close mechanism in a weatherproof galvanised housing. This also contains two powerful closing springs which in the service position are restrained by a lever released by a trip solenoid. An adjustable length of galvanised pipe couples the mechanism to a clevis on the switch. The MLE type FTS will make (without welding) closed on to a fault of up to40kA peak, withstand 20kA for 1 second, and is rated up to 72.5kV.

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