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rathakrishnan05
Active Contributor

Join Date: May 2011
Posts: 21

Cable Size Between Transformer to NGR and NGR to Ground

07/04/2012 3:24 AM

Dear All,

Could somebody explain me about the cable size between Transformer Neutral to NGR and NGR to Ground. I have used the formula I^2xSqrt(t)/K for the cable between Neutral to NGR. I dont know whether the same cable can be used between NGR to ground. Please guide me I will be very thankful to you. Please correct me if I am wrong.

Regards,

D. Madhu
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PWSlack
Guru
United Kingdom - Member - Indeterminate Engineering Fields - Control Engineering - New Member

Join Date: Jan 2007
Location: In the bothy, 7 chains down the line from Dodman's Lane level crossing, in the nation formerly known as Great Britain. Kettle's on.
Posts: 32175
Good Answers: 839
#1

Re: Cable size between Transformer to NGR and NGR to Ground

07/04/2012 3:55 AM

It's all in British Standard 7671, as has been indicated in these fora 7671 times now....

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debata07
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Join Date: Nov 2011
Posts: 131
Good Answers: 5
#2

Re: Cable Size Between Transformer to NGR and NGR to Ground

07/05/2012 1:54 AM

Yes. If the earth fault current is restricated to 500A say, by using NGR and earth fault withstand time is 3 sec, then minimum cross section will be 500 x 1.732/ k . Value of k for Al or Cu to be substituted in the formula to get the result
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1boybk1
Member

Join Date: Jul 2012
Location: Hanoi, Vietnam
Posts: 7
#3

Re: Cable Size Between Transformer to NGR and NGR to Ground

07/05/2012 7:57 AM

What does NGR stands for?

may be, NGR stands for Netral grounding resistance.
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debata07
Power-User

Join Date: Nov 2011
Posts: 131
Good Answers: 5
#4
In reply to #3

Re: Cable Size Between Transformer to NGR and NGR to Ground

07/05/2012 11:58 PM

Yes. NGR stands for Neutral Grounding Resistor.
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electricalexpert65
Guru

Join Date: Oct 2009
Posts: 2061
Good Answers: 169
#5

Re: Cable Size Between Transformer to NGR and NGR to Ground

07/08/2012 3:01 AM

Pl. check your formula. It is not I2 Root 't' / K, but only I Root 't' / K.
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1boybk1 (1); debata07 (2); electricalexpert65 (1); PWSlack (1)

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