I believe the subject MV switchgear has two incomers and one bus coupler. The design is such that the two incomers cannot be paralleled.
The key interlock ensures that no more than two breakers can be ON at any given point of time.
For example, if two incomers are closed, the two keys are locked in the respective positions. Bus coupler can only be closed, if one of the incomers is switched off and the key thus released is inserted in the bus coupler position.
This is a positive way of ensuring that the switchgear fault level is not exceeded (by paralleling two incomers) at any given point of time.
Yes. The organisation that designed and built it can, and it should have made it available in the Operation and Maintenance Manual for the installation.
If it is not to hand for whatever reason than a couple of phone calls to it may well precipitate the arrival of a replacement. The phone number may well be attached to it on a label.
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How did those calls to the equipment manufacturer go, please?
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"Did you get my e-mail?" - "The biggest problem in communication is the illusion that it has taken place" - George Bernard Shaw, 1856
Some good answers here. Usually your first call for an answer would be to your responsible plant engineer (or even the HV electrician) - they know these things, don't be shy!
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