Reverse Power Relay

[hillbilly1]

It looks like a redundant power supply, are the mains motorized so if one fails, the other automatically takes over? Also they should be interlocked to where if a fault opens one the other will not close while the fault is still present.

 

[Cold Fusion]

Thanks, cf....

One question. You mentioned load as a deciding factor, but would 368.17 not require the OCP not to exceed the buss rating. If both transformers can feed the buss simultaneously, it would appear to be a violation of 368.17 ..............

Sorry for ignoring you - (What foolishness - no I'm not. The sun is out, summer is here. Kid and I are building a tree house. Wife and I are planting shrubs. Life just doesn't get much better.)

But back to this. I'm not sure. I've never put in or worked a double ended sub that did not have a tie CB. And, all I have here is a 2005 NEC. So you will have to tell me if that changed.

Also, does 368 apply? Is this a busway or a switchboard?

If 368 does apply, look at 368.17, ex2, which sends you to 450.6.A.3. Also see 450.6.A.4.

As I mentioned, I've never put one in with out a tie CB, but it appears the NEC allows the load to be limited by design.

cf

 

[jimmac49]

Might want to check your CB KAIC ratings and busbar bracing with both transformers feeding a fault.
Jim

 

[Cold Fusion]

So, Augie -

What happened at the meet? We're ready for the rest of the story.

cf

 

[augie47]

No final decision as of yet. The "engineered system" has, so far,taken precedence. In that In that 368.17 does not specify the type of overcurrent protection, the engineered system and current monitoring equipment have been accepted as overload protection.
The reverse power relay has been accepted as "back-feed" prevention, although I am still pressing for notification plaques at the 15kv switchgear alerting of the backfeed possibility and called for LOTO at the unit sub mains to be used rather than depend on the relay.