Back feedinging main gear

[krlyle1]

My company is installing a solar canopy system in our parking lot we will feed into the building from the inverter at 13.2 kv . Is there anything we should be looking at as far as our 22 year old S&C main gear is concerned as far as listings for back feeding ?

Thank you
Kevin

 

[jim dungar]

It kind of depends on how you are actually accomplishing the connection, for instance: Adding a second "main" device to the gear so that it looks like a dual main system is probably not a problem, however bringing a feed in through the 'load' side of a switch may be an issue.

When you back-feed a switch, its fuse clips and movable blades will still be energized even when the switch is open. This situation could definitely pose a hazard to workers.

 

[krlyle1]

There are safties built into the inverter for that. I really want to know if it has to be listed for that or do we have to spend $100,000 + on a new gear thats listed for that purpose?

 

[jim dungar]

15kV class equipment that is 20 years old probably was never "Listed" even when it was new.

What type of safeties are you employing to prevent the fuse and switch blades from being 'live' even when opened?


Have you contacted S&C for their opinion?

 

[krlyle1]

We hav'nt contacted them yet we assume they want us to buy a new gear and we would like to know as much up front as possible befor talking to them. The entire system has been engineered and the inverter will not supply power when theres a lose of utility. I am also told that safety is not an issue. The gear can handle the backfeed its simply an issue of it being listed for that use .

 

[krlyle1]

I was able to contact an engineer from the the Solar American board for codes and standards I was told it would only be an issue if there were some type of ground fault protection on on the gear itself and even then it probably would'nt be.We contacted S&C they will send us documentation allowing us to do it.Thanks for help as allways.

 

[tallgirl]

UL 1741 is what prevents the load side from being hot when the fuse or breaker is open. And for this some of us are grateful.

The bigger issue is opening a circuit where the current flows backwards. Not all gear can handle that.