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

ashokumarrk

 Profile Answers by ashokumarrk Questions by 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%

pradipsabar2009

 Profile Answers by pradipsabar2009 Questions by pradipsabar2009

• Jul 29th, 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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Why armature control is used, not the field control for DC motors?What is the drawbacks in field control method?

chiragmistry

• Mar 14th, 2014

In case of the dc motor the armature control mathod is used blow the based the motor is run below the based speed Because,above based speed motor react as generator.

AHORDZI ERIC

• Nov 20th, 2013

What is ammeture reation

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