Page 110 - CITS - Electrician - Trade Practical

ELECTRICIAN - CITS

EXERCISE 46 : BDV Testing of different transformer oils

Objectives

At the end of this exercise you shall be able to
• identify the different types of transformer oils and grades.
• check & identify the parts, rating of BDV testing equipment.
• practice to operate the BDV testing equipment.
• perform the BDV testing of different transformer oils.

Requirements

Tools/Equipments/Instruments Materials/Components
• Combination plier (165mm, insulated) - 1 No. • Transformer oil sample (Any grade) - 2 or 3 meter.
• Screw driver (150mm, insulated stem) - 1 No. • PVC wire (2.5 sq.mm) - 2 m
• Neon Tester (75mm, 500 V) - 1 No. • Rubber hand glows - 1 Set
• Electrician knife (Insulated) - 1 No. • Cotton waste - as reqd.
• BDV testing equipment (60 KV) - 1 No.

Procedure

TASK 1 : Check the rating of BDV test equipment
1 Collect the Tools, equipments and materials required for experiment.
2 Draw the circuit diagram of BDV testing of transformer oil.

3 Collect 2 to 3 samples of transformer oil with different grades.
4 Check & identify the parts and rating of BDV testing equipment.
5 Place the BDV testing kit and oil samples on wooden table.

TASK 2: Perform STAR - DELTA Connection of transformer and connect to the supply
1 Open the testing cabinet of BDV testing equipment and connect the HTV terminals to ground for discharging
the static charge.
2 Take out the oil testing bowl of BDV testing equipment and adjust the gap of 2.5mm between the electrodes.
3 Pour the oil sample in glass oil testing bowl in such a way that both Electrodes are fully immersed in the oil.
4 Close the lid of glass oil testing bowl and carefully place it across the HTV terminals of BDV tester.
5 Close the testing cabinet and connect the BDV test equipment to 1 ph. AC supply socket.

6 Switch ON the supply and press the HT start push button of BDV testing equipment, observe the voltmeter
reading & indicating lamps.
7 Slowly turn the knob of auto transformer to increase the HTV voltage of BDV test equipment.

8 Increase the voltage until a spark occurs between the electrodes and equipment get trips.
9 Now press the memory push button and observe the HT voltage in voltmeter & record it.
10 The recorded HT voltage in voltmeter is the BDV value of tested transformer oil.
11 Repeat the test procedure of same oil sample 3 to 4 times and record the BDV value.

12 In similar way, perform the BDV test for different grades of transformer oil samples.

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