Power Lines Protection

Why the 1st zone of protection relay is 90% not 100%?

Questions by amektk

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pradipsabar2009

  • Jul 28th, 2010
 

If we consider the 100%, 100% in the sense there is another CB present there. so there is a dilemma which CB should operate first. Hence the first zone of protection is never 100%

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ashokumarrk

  • Nov 14th, 2010
 

Zone-1 protection is 80% in (NTPC, POWER GRID, NPCIL, NHPC, BBMB....) bcz we have consider the errors in CT, PT and also the line length. Datas provided should be same as the actual, but it wont. In order to compensate all these Zone-1 protection is 80%

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