Transformer Oil Testing

Transformer Oil Test is conducted to determine the Di-Electric Strength of the Transformer oil. It is also known as Break-down Voltage (BDV) Test. 

BDV TESTING KIT

Why di-electric Strength is important?

Transformer Oil is an insulating and cooling medium of the transformer. BDV Test is conducted to find out the voltage at which insulation or di-electric breaks down in the oil. Based on that BDV we can conclude that oil can be used or not as insulating medium for transformer.

Importance of its periodical checking

After the first commissioning of transformer, day to day it faces some challenges like atmospheric air, moisture, etc., Due to this, transformer oil can lose its quality. sometimes due to the internal faults in transformer can cause problem in the oil. Due to this, insulation failure may occurs in that. That is the reason to carry out Transformer oil filtration and BDV Test.

Precautions to carryout the BDV Test

• The gap between the electrodes inside the testing cup is adjustable with the help of screw outside the jar.

• Oil should be filled in way such that it should be above the electrode. It remains open for 5mins once it is filled with oil, to exhaust the bubbles or any air molecules in it. After that it has to be closed with glass door

CIRCUIT DIAGRAM OF BDV TESTING KIT

Procedure

Once oil is placed in the testing cup, Adjust the position of the variac to zero and close the ‘S’ switch. Push the on button. The supply ‘220V AC’ will energize the coil of the ‘M‘ Contactor. Due to this, the M1, M2 normally opened contacts gets closed. So the step-up transformer circuit closed and connect with varies. When you start to raise varies voltage, the switch S will open. The ‘M’ contact energizing through M2 (no) an it remains in ON position.

• Voltage in the step up transformer should be adjusted from 1KV to more. It should be adjusted 1KV/sec up to 22KV. At 22KV it remains undisturbed for 1mins

• After 1mins, again it should be adjusted for 1KV/sec. between (22-33KV) dielectric breath down occurs. It cause surge in primary winding and it cause the energisation of B coil of contactor. It cause the B1 (NC) contact to open. So, the supply M contactor cuts off so that M1, M2 will open the primary voltage turned off

CONCLUSION

    If the BDV breaks after the permissible level. The condition is satisfactory. So that the transformer can be used further. It it fails. We have to look up for servicing the transformer.