Tie Breaker
Tie Breaker
(OP)
A 600v bus is fed from two transformer connected each side of the bus through breaker. A tie breaker is between the east and west side of the bus.
Customer is reaching the maximum capacity of one of the transformer. I asked why we can't close the tie breaker and transformers can share the load. They looked at me like it was a very dumb question!!!
It raises many issues, higher fault level. That was only one concern. I appreciate any feedback on the subject.
Customer is reaching the maximum capacity of one of the transformer. I asked why we can't close the tie breaker and transformers can share the load. They looked at me like it was a very dumb question!!!
It raises many issues, higher fault level. That was only one concern. I appreciate any feedback on the subject.






RE: Tie Breaker
RE: Tie Breaker
To operate with the tie closed (transformers in parallel), you will need specialized overcurrent protection. In north America, this is commonly referred to as a "spot network". This commonly requires directional current sensing. This would be a job for an experienced engineer.
RE: Tie Breaker
If the original design was done with closed tie operation in mind, it is highly likely that present operation would be closed tie. Since the present operation isn't closed tie it is highly unlikely that you can make closed tie operation work.
RE: Tie Breaker
RE: Tie Breaker
RE: Tie Breaker
While technically it is possible to parallel the transformers, by closing the tie there are other aspects to be considered.
1. If the dual ended substation (two-transformer) design was originally implemented for redundancy, that is to maintain power upon failure of one of the transformers or the service, operating in them parallel defeats that requirement. So paralleling the two units may not be a correct strategic answer.
2. Are the transformers fed from two utility services? Most utility companies would not permit parallel operation of customer transformers on two separate feeders, regardless of technical feasibility.
I think most other points are made earlier.
RE: Tie Breaker
RE: Tie Breaker
Yes, there is a key interlock between the tie and each breaker on the secondary of each transformer, meaning one should be open to close the tie.
Switching loads is not easy. There are cables that need to re-rout and other complications.
dinkelja"
One purpose being to prevent back feeding of a faulted primary feeder.
You mean if a fault happens at the primary of one transformer the other transformer will contribute to that?
or you mean it prevents back feeding of a faulted secondary feeder?
RE: Tie Breaker
RE: Tie Breaker
Another note, which I did not see mentioned above -- presumably, the whole reason that a double-ended substation was originally provided was to ensure redundancy in your transformation. If your load has grown to the point where it exceeds the rating of a single transformer's maximum rating, then you have lost that redundancy. Which is just fine, so long as you realize that this has happened. In the event of a failure, you will be down until the transformer is replaced; if you have redundancy, all you need to do is switch to the other transformer.
Here is another consideration, which might well be a solution for you: fan rating. Do either of your existing transformers have fan cooling? If not, it could probably be added. That will usually buy you about 12% additional capacity. If you don't have fans, this may be an easy out for you.
RE: Tie Breaker