Answer / pillay

It is transformer oil dielectric breakdown voltage.
A sample of the tx oil is collected and tested with a
special tester. In the tester is a pair of electrode spaced
as per BS
spec. A TEST VOLTAGE IS APPLIED ACROSS THE ELECTRODES , and
this voltage is gradually increased until a breakdown
happens resulting in sparks across the electrode, immeadetly
the test voltage is stoped and the RMS voltage is
calculated.A few test is carried over and the mean voltage
is taken as the breakdown voltage of the sample oil under
test.

It is flash point of oil.The flash point is at what temp the
oil would self ignite. This depends on the quality and type
of oil.

Actually why the transformers are rated in KVA.?

4 Answers   BSL, Engineering,

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Why transformer neutral is earthed

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Dear All, In a 400V power system, ratio of three current transformers installed incoming switchgear is 4000/1. Maximum three phases short circuit current of this system is 48kA. One CT is installed on neutral of upstream transformer (6/0.42kV, solidly earthed) for 51G protection. Would you please inform me about the correct CT ratio of this current transformer (on neutral)?? Thanks a million

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1 Answers   Power Grid, Vignan University,

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