12kV Fusible Switch - Backfeed

Could you be more specific? Are you talking about backfeeding into the grid? Could you provide a drawing of your proposed wiring diagram? Are you an Electrician?What type of generator is it? What are it's specifications?

It is an existing 12kV, 1200A 3w+g switchgear lineup. I will be racking out the Main circuit breaker to test it and was wondering if a generator could connect to the load side of one of the fusible switches.

I know LV circuit breakers must be designed for this operation...

Well from the information you've given, I don't see why not, but without a first hand inspection of the system and proposed alteration, I can't really make a recommendation...

Isn't this the same as feeding the circuit downstream of the switch with a generator?

If so, then why install the switch at all?

You said...

"It is an existing 12kV, 1200A 3w+g switchgear lineup."

Those numbers make no sense. A 1200 amp switch rated for 12kV is over 14 MVA. That is one honking huge switch.

I am glad you "live2learn", without sounding condescending, perhaps this one is not the one to learn on. The simple fact you are asking this question in this forum scares me.

Leave the playing on this system to someone properly trained in the care of such a system.

Perhaps I am wrong and it was a simple typo that you entered. Take it as gospel, a 12kV station is real not forgivving to "oops".

Actually, 1200A is a common size of manual disconnect switch at 12kV (600A and even 2000A are also found). The main issues for the OP to address are the following:

1. That the main breaker for the normal supply is racked out and locked in a position that there is no possible way that the generator and the utility could feed the loads at the same time. Without proper synchronization and protection equipment, the results could be dramatic! Also, that there are no other sources of power feeding into the switchgear.

2. That the generator is of adequate capacity to supply the load the OP wants to run.

3. That the generator electrical equipment includes the appropriate protections and controls (AVR, under/overvoltage protection, under/overfrequency protection, reverse power, reverse phase rotation, etc.) that are required for a generator of that size and application. A disconnect switch of the type he describes may have fuses, but those would not be acceptable protection.

4. That the connections be made with attention to all applicable codes and specifications for the voltage level, location & AHJ, and application.

This is not a job for your average electrician, but rather a person or firm who is qualified and experienced in working with medium-voltage equipment and applications.

Thanks for the construtive reply. I knew it was common (larger) size. Just looking for a quick sanity check.