Upgrading the ampacity off a buss

[wfowfo]

We are a utility serving a plant that has a dual feed. We are wanting to take one of our transformers out for repair and shift the load to the other. The second bank is sufficient to handle the load, but the plant says that the buss work is not rated to handle the load (ie- a 2000 amp buss that needs to carry 2500 amps).

The buss is a 40 year old GE product. The plant is making noises about having the buss "re-rated " to handle the additional load (an approximately 25% increase).

Has anyone ever heard of having a buss "re-rated" to be able to carry a higher current? If so, how did they go about it?

 

[wareagle]

The rating has everything to do with temperature and heat transfer. Your rating may be at a higher than normal temp for the location. Check here for more information.

http://64.90.169.191/applications/busbar/homepage.html

 

[AusLee]

The bus is already rated at 125% of the rating of the transformer. So if the kVA rating of the tranformer is larger than the sum of the two loads, you have no problem.

Power factor on the feed can reduce the amps from the transformer so if you have any installed it can work for you.

Take measurements and show them that your loads are never ON all at the same time, propose a duty cycle.

Have them bring in a replacement transformer while one is being repaired. Press them with time or claim that because it's holiday season the load is reduced, although a trafo repair can take one month!

 

[wfowfo]

Quote:
"Have them bring in a replacement transformer while one is being repaired. Press them with time or claim that because it's holiday season the load is reduced, although a trafo repair can take one month!"

Trouble here is, we ARE the utility. We are trying to work with this plant to make this work for everyone. We already committed to transformer changeouts 4 years ago to make sure either transformer could hold the load if the other failed. However, nobody checked their buss to see if it could.

Now that the situation has finally occurred, the only solution at this point is to try to get more ampacity out of their buss. They are not sure how to approach the problem and we are trying to help.

 

[wareagle]

wfowfo
What is the actual measured load? Is it greater that 2000 amps? If the buss is a 40 year old GE product it may not be able to be re-rated. I assume you have checked with GE.
Is the buss in open air in a switch yard or something enclosed?

 

[wfowfo]

The load is just under 2500 amps (at 480 volts) on a 2000 Kva transformer. The buss is enclosed, but is in an airconditioned building.