Answer / arun_sekar_1986

1.Power Factor is defined as the cosine angle between
voltage and current.
From Power triangle cosine angle is defined as the adjacent
by opposite side.
ie., cos angle=kW/kVA


2. 51-AC Time Overcurrent Relay is a relay with either a
definite or inverse time characteristic that functions
when the current in an ac circuit exceed a predetermined
value.

87-Differential Protective Relay is a protective relay that
functions on a percentage or phase angle or other
quantitative difference of two currents or of some other
electrical quantities.

Answer / gunasekaran

low P.F following effect will accure.
1.KVA=KW/PF for low PF KVA ratng so equipment size will
incress.
2.PF is low more current so transmission loss will more.and
conductor size also incress.
3. poor voltage regulation
4.M.d incress.
51-idmt o.c and earth fault
87-diffrential relay it is operating B/W primary and sec
current diffrence.

Answer / vinod shnde

Mr. arun,cosangle=adj side/hypo

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