Answer Posted / raj
before doing tan delta test, just we know that its for
determine the condition of insulation to the equipments.and
it has more benefits when compared to meggering(IR).megger
means to find insulation only behinds surface condition.but
for tan delta/dissipation factor/loss factor/power factor
is to determine internal void conditions, and their
capacitances.
permissible limits of tan delta for all bushings - 0.7%
then important one while testing of tan delta, we should
take the current test temperature, then correct that one to
20*c. . .
for that correction we should take the values from the
correction table that we do by using specific testing kit.
for megger make,doble,eltel we have different tables. just
refer and correct it.
impt: it will be compare with factory reports only after
correction of values to 20*c
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