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Anonymous Poster

Discrimination Between CBs

10/04/2010 7:11 AM

Hi all We have upstream breaker 400 A and down stream 100 A . How can we achieve best discrimination between them by time and current both .

Can any one explain any good thumb rule .

Manmohan
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ikhanuk
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Join Date: Aug 2009
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#1

Re: Discrimination between CBs `

10/04/2010 7:16 AM

Hi Manmohan

Is these are on same voltage levels no pri sec involve ?? otherwise you have to translate it on either side like LV then compare the curves of your breakers on OL and SC side .You didnt write the manufacturer name in post .However upstream CB >= 1.6 times Downstream breaker better to use the tables provided by manufacturer up to what limit these are discriminated .

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ikhanuk
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#2

Re: Discrimination between CBs `

10/04/2010 7:25 AM

1

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jack of all trades
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#3

Re: Discrimination Between CBs

10/04/2010 2:58 PM

As others have said you need to follow the wise advice of the Jedi master Yoda from the Star wars movies - "Consult the circuit breaker curves you must if discrimination you seek".

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PWSlack
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#4

Re: Discrimination Between CBs

10/05/2010 6:51 AM

Buy a copy of British Standard 7671, perhaps?

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