Answer / zahid noor

Minimum dielectric strength of transformer oil is a wrong
question itself, For New insulating transformer oil, the
value is 70kv, where as oil in use has values ranging from
25 kv to 50kv , depending upon various factors like ,
running hours of use, impurities, moisture content, sludge
content etc, but it is advisable to discard old oil, if
value does not improve after filteration above 30 KV

Answer / pundlik wanwe

transformer oil BD value is a relative term and as a matter
of fact we can use the oil of different break down value
depending on the transformer voltage ratings.
1) For the transformer voltage rating more or equal to 145
kv BD value of oil should be more than 65 kv and moisture
content should be below 15 ppm.
2)for the voltage rating below 145 KV BD value should be
45KV and moisture content of less than 25 ppm.
More more information please refer
a) IS: 1866 for oil in service.
b) IS: 335 for new oil

Answer / phani

please send this answer to me also

Answer / rahul

30kV(peak)/cm_(it occurs for untreated oil)

Answer / irfan ahmed farooqui

For a new insulating transformer oil(called virgin oil),
the,
value is 70kv for a good satisfactory level but, where as
oil in use (called in service) has values ranging from 25
kv to 50kv , depending upon various factors like ,running
hours of use, impurities, moisture content, sludge content
etc, but it is advisable to discard old oil, if value does
not improve after dehydration and filteration above 60 KV
in laboratory setup or the oil has not passing a
compatibility/mixibilty test with new transformer oil at
different ratio to come to at par in usable ranges as per
standards, on the other hand the exact values and correct
figures for Virgin oil are available in IEC-60296 AND for
oil in service there is a complete guide and specification
available as IEC-60247 where all the nesseccary
informations are available,including the test methods and
apparatus required.

Answer / ratnesh dubey

60Kv at 4 mm gap for 1 minute.

Answer / k.prakashchandra

As per IS 1866:2000,50KV for 170 KV &above,40 for
72.5-170,30 for below 72.5.

Answer / chakri

according to BDVT 2.5MM distance withstand at min 40kv
so min dielectric strenght is 40kv

Answer / ajay kumar das

It should not be less then 36 KV for 1 mint.with 2.5 mm air gap

Answer / prasad shah

BDV of transformer oil ig generally 40 to 45 KV for used
oil.and new it is around 60 KV.Also it is depends on
incoming voltage to transformer and rating of transforemr

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