How to protect power transformer 630kVA 1

[nayden]

Hi
I have a discussion with my colleagues regarding best protection performance for power transformers 630 kVA. According to their demands it should be executed by MV Fuses(lower price), but my personal opinion is rather different and I think that the wright choice is by circuit breaker and overcurrent-time protection.
I am kindly asking for your opinion!

 

[davidbeach]

It depends. It depends on many factors, but most of them eventually boil down to cost. 630kVA is small and, for a North American, a very strange number. Fuses are more common for the smaller transformers and breakers & relays more common for larger transformers. I would expect that most power transformers less than 2000kVA are protected by fuses and breakers & relays become more common above that, but I've seen fused 5MVA transformers.

If you do go with breaker and relay, I'd recommend a numeric differential relay. That way you would have both overcurrent, on both sides of the relay, as well as differential.

 

[wbd]

I agree with davidbeach. That is a small transformer and I would protect it with fuses. Usually fuses are used for transformer protection up to 5 MVA. The cost to install breaker or circuit switcher and relaying is not economical for small transformers.