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Grounding Transformer

Grounding Transformer

Grounding Transformer

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

RE: Grounding Transformer

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.  

RE: Grounding Transformer

(OP)
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.

RE: Grounding Transformer

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

RE: Grounding Transformer

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.  

 

RE: Grounding Transformer

(OP)
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!!

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