DIELECTRIC OIL TESTING USING H.T TESTING KIT

Aim: To measure the breakdown voltage of dielectric transformer oil.

Apparatus: H.T. testing kit

Test Method:

The test cell with same cell filling upto 6 times for carrying out the test. The

first application of the voltage is made as quickly as possible after the cell

has been filled, provided there are no longer ant air bubbles in the oil and at

least 10 min after filling. After each breakdown the oil is gently stirred

between the electrodes avoiding the possibility of air bubbles. For the

subsequent five tests the voltage is replaced one minute after the

disappearance of any air bubbles that may have been formed. If the

observation of the disappearance of air bubbles is not possible it is

necessary to wait five minutes before a new break down test is started.

The electric strength shall be the arithmetic mean of the results, which have

been obtained.

Procedure:

1. Switch on the mains by means of main switch, the condition will be

indicated by means of pilot lamp.

2. Keep motor switch in decrease position.

3. Press operate push button. The motor will start operating and control

knob will move anticlockwise tending towards zero position keep the

OPERATE push button till the control knob comes to zero where the

switch logic will actuate contractor (CM) and H.T is on toggle motor

switch in OFF position.

4. Toggle motor switch in INCREASE position. The motor will start

operating and voltmeter will start reading the voltage generated by

high voltage transformer and control knob will start moving clockwise.

The rate of voltage rise will be 2 KV/second.

5. Test the sample of desired voltage by toggling the motor switch in OFF

position. The voltage will automatically increase OR decrease

depending upon the motor switch position. If the sample fails it will

trip the H.T. contractor by receiving signal through circuit breaker

(C.B.)

6. The voltmeter will indicate the voltage at which the sample has failed.

The memory circuit will allow the meter to indicate the break down

voltage. The high tension cannot be made on unless the output

voltage of control transformer comes to zero.

7. To energize the H.T. once again adopt the procedure laid as per

mentioned above in operation.

Precautions:

1. Do not rise the voltage at a faster speed then recommended if the

same is manual operated.

2. Always clean the test cell before use and observe practice laid in

specifications.

3. Clean the massive supports, which are on insulated support of the

transformer.

4. Clean the TFR top and remove the oil traces from it. Use supplied

spongy plastic piece to collect oil traces from TFR.

5. Do not stress the voltage to the voltage to the electrodes when the test

cell is empty. The applications of voltage will cause damage to the

electrode by excessive sparks.

6. The equipment is scientifically designed and it is backed by

manufacture’s defect guarantee.

Tabular Column (observations)

S.No Distance between electrodes in mm

Breakdown voltages of consecutive tests in (kV)

Result:The break down voltage of dielectric oil is …….KV.