Kirk Key interlock for loop feed transfomers

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dahualin

Senior Member
We have six loop feed transformers that are fed from a Main-tie-Main MV switchgear. The loop shall be kept open all the time, otherwise it will be a big accident when two services form different substations seeing each other. The loop feed transformers are using loop feed T-blade switches. So one of the T-blade switches shall be able to be locked at open position. Have you guys used Kirk-key interlock for this application? Any info is welcome. Thanks. :confused:
 

augie47

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Location
Tennessee
Occupation
State Electrical Inspector (Retired)
If I understand your arrangement, we did something similar once by installing some bolt type locks (similar to a drawwer lock) on disconencts to prevent operation and had the keying set up like a kirk-key arrangement.
 
We have six loop feed transformers that are fed from a Main-tie-Main MV switchgear. The loop shall be kept open all the time, otherwise it will be a big accident when two services form different substations seeing each other. The loop feed transformers are using loop feed T-blade switches. So one of the T-blade switches shall be able to be locked at open position. Have you guys used Kirk-key interlock for this application? Any info is welcome. Thanks. :confused:

The basic setup for this would be of having -1 key of identical locks. The lock allows the breaker or switch to be turned ON when the key is inserted AND turned, and you have to turn the switch off in order to 'unlock' the lock and remove the key. This setup assures that there is always an open loop.
 

dahualin

Senior Member
The basic setup for this would be of having -1 key of identical locks. The lock allows the breaker or switch to be turned ON when the key is inserted AND turned, and you have to turn the switch off in order to 'unlock' the lock and remove the key. This setup assures that there is always an open loop.
I am thinking if the kirk-key interlock system can be fool-proof for loop feed transfomrers. In main-tie-main MV switchdgear we designed KirK-Key system that you cannot take the key out unless you lock the circuit breaker at open position. I have debated with manufacturer about using Pad-lock kirk-key system that doesn't seem fool-proof. What do you think?
 

augie47

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Staff member
Location
Tennessee
Occupation
State Electrical Inspector (Retired)
I could not come up with a way using padlocks...too easy to defeat any plan I had, so we used the slide bolt locks (may not be the right term, similar to a desk lock, but heavier). The locks are riveted in place and keep the disconnect handle locked. Typical (1) key, removeable in locked position only.
 

zog

Senior Member
Location
Charlotte, NC
We have six loop feed transformers that are fed from a Main-tie-Main MV switchgear. The loop shall be kept open all the time, otherwise it will be a big accident when two services form different substations seeing each other. The loop feed transformers are using loop feed T-blade switches. So one of the T-blade switches shall be able to be locked at open position. Have you guys used Kirk-key interlock for this application? Any info is welcome. Thanks. :confused:

I see this type of application in open pit mining applications quite often and they all used a key interlock system. Should be an easy one to configure. What is the type of switch you are using?
 
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