double end substation

[john d]

If i have a double ended substation with a main-tie-main 480v and each transformer is 1000kva is 100% redundency required or is it legal to load 800kva on the left side of the tie and 800kva on the right side of the tie.

 

[ron]

As long as the overcurrent protection is correctly sized, I see it as a bad design condition, but not a code violation.

 

[charlie b]

You could leave one side unloaded completely, and put nothing more than a single 100 watt light fixture on the other side, and the NEC would have nothing to say about it.

 

[john d]

When the tie is open all is good but if a main failed and was turned off and the tie was closed the transformer would be overloaded. this concerns me.

 

[ron]

John,
As mentioned, it would concern me too as a poor design, but I don't think it is a code violation.
You could easily add a shunt trip so that when (just before) the tie closes, it shunt trips a portion of the load to bring it within ratings and not trip the active main.

 

[mull982]

We have a similar installation here at our plant. We have two 3000A main breakers to two pieces of switchgear and a 3000A tie breaker between the two sections of switchgear. Two identiacal plants of close to 3000A are served from each section of switchgear. The two mains are served from two seperate utility transformers which cannot be paralled. The tie breaker is only for emergency cases, where a transformer is lost, and one transformer cannot run both plants, so we have to shed some load on both plants to run parts of both plants for emergency loads.

 

[wasasparky]

I will assume the 1000kVA transformers would be yours?
You can look into dual rated transformers (w/ fans) to help...
Load management can also help.
This is a design issue, not code...