Pls Explian BDV TEST of transformer oil

BDV = breakdown voltage. Sounds like a Google project....

Transformer oil testing procedure:

To check the insulating property of dielectric transformer oil, a sample of the transformer oil is taken and its breakdown voltage is measured.

• The transformer oil is filled in the vessel of the testing device.The gap between
  the electrodes shall be 2,50 mm ± 0,05 mm in the testing device.
  
• Apply voltage to the electrodes and uniformly increase voltage from zero at the rate of 2,0 kV s^-1 ± 0,2 kV s^-1.
• At a certain voltage level breakdown occurs in an electric arc, leading to a collapse of the test voltage.
• An instant after ignition of the arc, the test voltage is switched off automatically by the testing device. Ultra fast switch off is highly desirable, as the carbonisation due to the electric are must be limited to keep the additional pollution as low as possible.
• Record the value.
• Carry out six breakdowns on the same cell filling allowing a pause of at least 2 min after each breakdown before re-application of voltage. Check that no gas bubbles are present within the electrode gap.
• Calculate the mean value of the six breakdowns in KV.

Conclusion: The lower the resulting breakdown voltage, the poorer the quality of the transformer oil!

Vinu_answers Sure_Answers

• Collect the oil sample of transformer oil from the bottom valve of the transformer
• Pour the oil sample in oil pot of the machine.
• Keep the oil pot in open air for 5 Minutes so that air bubble if any gets out.
• Now put the oil sample in the machine.
• Increase the KV at the rate of 2 KV/Sec and observe the oil sample through a glass window.
• Continuously observe the oil sample through an inspection window while increasing the voltage.
• Note down the KV at which sparking is observed in the oil. The voltage at which sparking observed is the breakdown voltage of oil.

• Repeat the step No. 4,5,6 & 7 for the same sample for six times and note down the breakdown KV in each case.
• Take the average of BDV values observed in step7 & 8.
• If oil BDV value is above 30KV, oil is OK for use.

Read More: Transformer oil BDV Test Procedure