Grounding Transformer 1

[Ysaac]

Any of you could help me to find out how to calculate a grounding transformer to a generator ?

 

[dpc]

Where have you looked so far? Since you haven't given us any information at all, no one is going to be able to help you.

There are some good references - Protective Relaying by Blackburn might be a good starting point.

 

[Ysaac]

DPC, excuse me if I did not clear, but what I'm looking for is a methodology that teaches how to calculate a transformer grounding for generators.

I could calculate the power transformer considering steady state, which would be very easy. But I what I have read shows that the grounding transformers are designed to take from 1 to 10 minutes on lack. In my case, I want to Dimenssion it for 1 minute. I think there should be a methodology or a standard rule for this, which I know of. So I'm asking for help.

More specifically, I want to calculate a grounding transformer for a 70MVA generator. The maximum fault current that must circulate through the center star in case of a fault (short circuit) to ground is 10A. The voltage-phase generator is 13.8kV, and the grounding transformer must be able to suport a falt condition to the ground for one minute at most.

Tank you for your help.

 

[alehman]

I've usually seen them sized for the required current and voltage, without consideration to the time rating. 8kV * 10A = 80kVA. You could probably manage with less, but the cost difference is small.

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

 

[dpc]

Purchase "Industrial Power Systems Grounding Design Handbook" by Dunki-Jacobs. This topic is well covered there. The old "Applied Protective Relaying" book also covers this, though not as completely.

What you are talking about is better described as a neutral grounding transformer for a high-resistance grounding system.

 

[Ysaac]

DPC, thank you a lot !!! this book is really great and it´s gonna help me with this and many others daught.

Thank you one more time!!