Restricted earth fault protection 1

• Aug 17, 2017

• #2

davidbeach

Electrical

Mar 13, 2003

9,550

US

Assuming that you're already committed to using a relay rather than fuses, the only questions would be whether or not the transformer has a neutral (isn't a delta-delta transformer) and whether or not all of the necessary CTs exist. Beyond that deploying REF is simply turning it on and including it in the trip equation.

 

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• Aug 18, 2017

• #3

ZeroSeq

Electrical

Apr 17, 2014

84

CA

See section 16.7 of "Network Protection and Automation Guide" by Areva for an explanation on the uses of restricted earth fault protection. It depends on your system, grounding method, transformer size, how sensitive you want your differential elements, etc.

 

 http://files.engineering.com/getfile.aspx?folder=52582cb3-2436-491a-9f0d-cc006af420ca&file=Transformers_Percent_of_Protected_Windings.JPG

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• Aug 18, 2017

• #4

bacon4life

Electrical

Feb 4, 2004

1,543

US

REF does provide more sensitive protection for some kinds of faults. However, there is a nominal cost of understanding how to properly set and test the REF element. Just because an element is available from the relay, it doesn't mean you have to use it.

 

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• Aug 20, 2017

• Thread starter
• #5

Ampereturns

Electrical

Aug 17, 2017

2

GB

Hi,

I should have made myself clearer.

What factors would lead you to add or omit restricted earth fault protection in a particular situation ?

 

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• Aug 21, 2017

1
• #6

jghrist

Electrical

Jul 16, 2002

4,226

US

REF is more important with impedance grounded transformers because winding faults close to the neutral are harder to detect. The normal transformer differential protection will adequately protect solidly grounded transformers, but normally I would use REF if a neutral CT is available and the relay has the REF element built in.

 

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