Transformer PPM (Preventive Maintenance Plan)

1. Daily

• Check oil level in the conservator.
• Observe transformer and winding temperature indicators.
• Verify proper operation of cooling fans/pumps.
• Inspect for unusual noise, smell, or vibrations.
• Check meters for load current, voltage, and frequency.
• Record readings in the logbook.

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2. Weekly

• Inspect silica gel breather (replace if color changes).
• Check HV & LV bushings for cracks, dirt, or oil leakage.
• Verify control/protection relays have no alarms.
• Inspect earthing connections.

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3. Monthly

• Inspect for oil leaks (tank, gaskets, radiators).
• Clean transformer surfaces and bushings.
• Test insulation resistance (IR test, if schedule permits).
• Check OLTC (On-Load Tap Changer) oil level and mechanism (if applicable).
• Verify load readings against nameplate rating.

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4. Quarterly

• Test operation of protective relays (Differential, REF, Buchholz, Overcurrent, Earth fault).
• Test alarms and trip circuits.
• Check fan/pump interlocks.
• Test transformer oil BDV (Breakdown Voltage).
• Inspect surge arresters and lightning protection.

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5. Half-Yearly

• Perform thermography (infrared scan) for hot spots.
• Check mechanical tightness of connections and bolts.
• Inspect conservator diaphragm/bladder.
• Partial discharge (PD) test if applicable.

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6. Yearly

• Full transformer oil testing (BDV, Moisture, Acidity, Interfacial tension, DGA – Dissolved Gas Analysis).
• Calibrate meters and protection relays.
• Perform polarization index (PI) test.
• Check contact resistance of bushings & OLTC contacts.
• Inspect and service OLTC (oil filtration/change if required).
• Inspect core & windings during major shutdown (if permitted).
• Verify fire protection and alarm system operation.

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7. After Faults or Abnormal Events

• Inspect transformer immediately after tripping.
• Perform insulation resistance (IR) and continuity tests.
• Take oil samples for DGA if fault suspected.
• Check surge arresters after lightning events.

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