Oil-Immersed Transformer: Pre-Operation Checklist

I. Visual & Sealing Inspection
Verify structural integrity and sealing:

Check bushings, tank, radiators, and conservator for damage, leaks, or corrosion.

Ensure nameplate/phase markings are legible.

Confirm desiccant is blue and oil cup is properly filled.

Validate oil level matches temperature curve; oil should be clear.

II. Electrical Safety Verification
Perform essential electrical checks:

Test insulation resistance using megohmmeter in sequence: HV-ground, LV-ground, then HV-LV.

Ensure grounding resistance ≤0.1Ω and core is single-point grounded.

III. Oil & Cooling System Check
Confirm operational readiness:

Ensure all oil valves are fully open for circulation.

Verify tap changer position and gas relay oil level.

Confirm pressure relief valve is unobstructed.

IV. Key Maintenance Rules
Follow critical maintenance protocols:

Use only same-brand oil for replenishment.

Replace desiccant when >2/3 discolored; close throttle during replacement.

Maintain ground connections; address corrosion promptly.