500 KVA Three Phase Oil Filled Distribution Transformer

Certificate Verification: Verify the transformer’s certification. If the certificate is older than two months, retest the insulation resistance to ensure it meets the required standards.

Insulation Testing: Use a megohmmeter to test insulation resistance to confirm insulation integrity; perform a Dielectric Absorption Ratio (DAR) test to evaluate the insulation condition.

Oil Level and Quality: Check the oil level and ensure that ventilation holes are unobstructed. There should be no signs of oil leakage; sample the transformer oil and analyze its dielectric strength, moisture content, acidity, and dissolved gas analysis (DGA) to detect potential issues like overheating or arcing.

Insulation and Connections: Inspect high and low voltage bushings and associated wires for signs of damage; ensure all screws and connections are tight and secure to prevent electrical faults. Use infrared thermography to detect hotspots at connection points, which might indicate loose connections or corrosion.

Tap Changers and Fuses: Confirm the tap changer position is correctly set according to operational requirements. Inspect and clean the tap changer contacts and mechanism, and perform electrical tests to ensure proper operation.

Lightning Protection and Grounding: Check for any signs of damage to the lightning arrester; measure grounding resistance to confirm it meets safety standards, and verify the integrity of grounding connections and electrodes.

Cooling System: Inspect radiators and cooling fans to ensure they are clean and operating normally. Check the operation of the oil circulation pump (if equipped) to ensure effective cooling.

Noise and Vibration: Monitor the transformer for any abnormal noise or vibration, as this may indicate internal problems.