underfrequency protection for GSU 1

[vranac]

Hi...
I am wondering about few things regarding unnderfrequency Protection for genrator stepup transformer...So, if somebody could give some comments...
- is setting for trip is 47,5Hz for 1 second to short. Means should we give more time to try to come back in normal frequency
- is it necessary that transformer Protection trip generator braker or it is enough to trip only HV side breakers
- what could happened if Protection trip only HV side breaker and keep transformer still connected to generator...
- shall V/Hz Protection be setted to trip same breakers as the underfrequency Protection, something like a doublled Protection
thx

 

[slavag]

Underfrequency protection is generator protection, not GSU.
Not needed trip HV breaker, only GCB.

But, you can do decoupling trip for save generator and aux bus, this option is depend on the your application.

U/Hz is another issue, another type of protection, actually is generator protection too, but transformer is saturated faster than generator. In case of U/Hz tripped both HV and MV breaker.

 

[vranac]

Hi, thanks for replay....
Now when you mentioned that ''GSU is faster saturated than generator...'', is it possible to get some information or dana about how long it takes for transformer to be saturated. On what does it depends (exept on frequency). Is ther any formula how to calculate this? For example if we have transformer rated for 50Hz, and let say that it is working on 45Hz. Is he going to be saturated, and after what time? Is this time measured in let say 2minutes or it is more like 2hours or more? Is it possible to find those answers somewhere?

 

[slavag]

see here, hope its help

http://www.pes-psrc.org/Reports/J-5CoordinationofGen.Prot wcpyrt.pdf

 

[waross]

Very nice slavag. lps

Bill
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"Why not the best?"
Jimmy Carter