BDV of Transformer Oil at 4mm Gap

Vide IS 6792:1992, the minimum BDV of transformer oil across a contcat ghap of 2.5mm shall be:

30kV for voltages uptp 72.5kV

40kV for voltages above 72.5kV upto 170kV

50kV for voltages above 170kV upto 420kV

Bureau Of Indian standards, has set some norms for determining any process or activity that has to be accepted by all the industries manufacturing, supplying any product on commercial level.

For your question, IS-6792 describes the method of determining the electric strength of insulating oils. It clearly states that, the gap between the two electrodes (copper, brass, bronze or stainless steel polished) must be set within 2.5±0.01mm.

So, It is clearly mentioned in the standard to take BDV at 2.5±0.01mm, then why you want to conduct it at 4mm?

Now, Suppose if were a oil manufacturer and you conduct BDV testing at 4mm which not conforms to Indian or any globally accepted standards, then why customers will purchase your oil?

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