Switchgear

[jimbo123]

This is a question on switchgear that is controlled by a plc when there is a power failure and the bu generator is supplying power to the switchgear. If one CB in the switchgear is in the off position and left in place so the only thing to put the CB back in service would be to close the CB.

Our engineer said if the generator were to start up and supply power to the switchgear that it would try to close the opened CB. This to me doesn't sound right for that to happen, I have limited knowledge on SG and the plc start up.
Does anyone know either way about this operation ?

 

[jwr570]

It will depend on the program of the PLC.

 

[Jraef]

Define "SG" in your question. If you are referring to UL891 switchgear that is using Molded Case Circuit Breakers, the only way to close an MCCB that has been opened is with a motor operator, a VERY expensive option. So if someone has elected to pay for that option, there is usually a very good reason. Without it, you cannot close an MCCB remotely.

If you are referring to UL1558 / draw-out metal clad switchgear with power breakers, they come with motorize charging mechanisms anyway, so they are essentially designed for this purpose. So as jwr570 said, at that point it becomes a question of what the designer was looking for the equipment to accomplish after a power changeover. it's very common on large systems that use this kind of gear to open the breaker after a power fail, crank up the generator unloaded or with minimal load, and re-close the breaker once the power is stable again.

 

[jimbo123]

SG is a metal draw crank out power breaker.
thanks for your responses on this . I see i was wrong and learned i something new here. Great !