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protection of highvoltage transformer by cutoff fuse
2

protection of highvoltage transformer by cutoff fuse

protection of highvoltage transformer by cutoff fuse

(OP)
in our grid there are many cutoff fuse for protection of 30mva transformers,and one of our eng think fuses are  better than relay.it is right from your point of view?
he says for relay operation you need to dc,operate of relay,operate of breaker,operate of trip relay and so on.but fuse just operate.!

RE: protection of highvoltage transformer by cutoff fuse

A fuse is just a plain overcurrent device. It can not perform any of the multitude of functions which can performed by a relay. Ask how he would implement a biased differential scheme using fuses.
  

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If we learn from our mistakes I'm getting a great education!
 

RE: protection of highvoltage transformer by cutoff fuse

Pressed 'Submit' too quickly.

Furthermore, ask how would he integrate important mechancial protections such as the pressure relief device, Buchholtz, and oil & winding temp indicators into his fuse-based scheme.
 
  

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If we learn from our mistakes I'm getting a great education!
 

RE: protection of highvoltage transformer by cutoff fuse

(OP)
fuse is for backup .and my question is :"is it regular to protect a 30mv transe by fuse?".my friend sas it is regular in other countries.

RE: protection of highvoltage transformer by cutoff fuse

That's a very different question to the one you originally asked.
  

----------------------------------
  
If we learn from our mistakes I'm getting a great education!
 

RE: protection of highvoltage transformer by cutoff fuse

If money were no object, I'd have fuses in addition to the breaker or circuit switcher and relaying. For high current fault that have the fuse acting in less than 3 cycles the fuse will offer better protection. For everything else, relays plus interrupting device would be far better. In the real world where cost and space are concerns, the fuse is not even given consideration.  

RE: protection of highvoltage transformer by cutoff fuse

(OP)
we lost on of our transe for malfunction of a breaker.
and a fuse is cheaper than a transe.
and lost another although a breaker was operated.

RE: protection of highvoltage transformer by cutoff fuse

Apparently you forgot to implement a breaker failure scheme. There are faults for which no protection is going to save the transformer, but for most faults you can get faster clearing with relays and breakers/circuit switchers than any fuse can provide. I'd never do a large transform without differential and have yet to find a fuse that would do any good there. Fuses become a coordination nightmare if you try to stay under the transformer damage curve, but a differential never has coordination issues. Ever try to get really good protection for secondary ground faults using fuses on the delta side of a delta-wye transformer? No, I didn't think so.

Go ahead and just use fuses, but keep plenty of spare transformers on hand.   

RE: protection of highvoltage transformer by cutoff fuse

hilarious...

i had no idea other parts of the world actually relied on fuses to protect a transformer.  seems absurd to me.   

RE: protection of highvoltage transformer by cutoff fuse

It's pretty common in the US, up to a certain transformer size.  Older rural substation up to 15 MVA often have only primary fuses.  It's not a good situation and a primary circuit switcher or breaker would be a big improvements.

But fuse links for a 30 MVA is really not providing adequate protection for the transformer as others have mentioned.   

RE: protection of highvoltage transformer by cutoff fuse

Yes, sorry my mind was stuck in the HV world, I understand transformer size has a lot to do with it.  I was implying only highvoltage (say 15MVA and up) units.

That being said for low voltage transformers the new reclosers available these days are pretty sophisticated.  No differential capabilities but equiped with communications to downstream devices.

RE: protection of highvoltage transformer by cutoff fuse

I'll 2nd dpc's obervation. There are countless small substations in the central U.S. with only fuse protection for up to 115kV primary. I think the cost justification for a breakers and protection relays just wasn't there when most of these were installed. Modern circuit switchers and electronic relays may have changed that.

Alan
----
"It's always fun to do the impossible." - Walt Disney

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