Medium voltage switchgear question - Mike Holt's Forum

If we have (2) separate 15kV feeders come into MV switchgear and (1) feeder comes out of this switchgear to feed a MV transfomer. Two comning feeders, each terminates in a 200A fused disconnect switch inside MV switchgear. Can these two fused disconnect switches be kirk-key interlock switches type? (I knew we can do with medium voltage breakers but never know about the fused disc.).


The output feeder will comes to the medium voltage transformer. Do we need to have fused switch or breaker protects this transformer installed inside MV switchgear or it can be as part of transformer primary protection? Or do we need both, the MV switchgear is 100' away from the MV tranfromer. Kirk Key

Kirk Key

Sure, the two 15kV feeders can feed individual switches and fuses and be interlocked by Kirk Key.

As long as the Kirk Key permits only one source at a time to feed the transformer and uses an open transfer, there will always be only one source for the transformer. If the fuses are rated to protect the transformer correctly, they provide fault protection fot the cable to the transformer and overload protection for the transformer.

I do not believe there is a distance requirement that requires the fuses protecting a transformer to be within a certain distance of the transformer.

Sounds OK to me.

anbm said: ...key interlock switches type? (I knew we can do with medium voltage breakers but never know about the fused disc...

Key interlocks can be applied to any device at any voltage. Most manufacturers of MV fusible switches include key interlock provisions into their standard product, so field modifications are easy to perform.

FWIW: KIRK is a registered name of a specific type of key interlock. The current owner (since ) of this specific name is the Kirk Key Interlock Company

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