Daily Maintenance:The following items have to be checked every day in the shift1. Checking of Oil level in conservator and bushings and examining for leaks2. Checking for unusual internal noises3. Checking relief diaphragm for cracksThese items have to be attend by staff on shift duties and has to be recorded in daily log books of Sub-station. No columns are provided for these items in this register.

Monthly Maintenance:1. Cleaning of bushings and checking for any cracks2. Checking the color of silica gel in the breather and replacement or reconditioning if necessary.3. Inspection and cleaning of breather4. Ensuring that oil comes out when air release valve is opened5. Checking the oil level in the inspection glass of buchholz relay

Quarterly Maintenance:1. Measuring insulation resistance of windings with 2.5kV Megger 2. Checking up of temperature alarms and buchholz alarms for correct operation.3. Testing of Oil for the dielectric strength above 1000kVA (Tank and Tap changer)4. Checking buchholz relay for any gas collection and testing the gas collected by passing through nitrate solution.5. Checking transformer ground connections for tightness.

Half Yearly Maintenance:1. Testing of oil for the Dielectric Strength (Tank)2. Checking up gap settings of the bushings on the transformer of 66kV and above

Yearly Maintenance: 1. Calibration of temperature indicators2. Testing of oil acidity (Tank, conservator, Tap changer)3. Checking operation of buchholz relay by air injuction4. Overhaul of tap changer5. Tan Delta Test should be conducted 6. DC winding resistance should be measured

Filtering and replacement of Oil:1. Tank and conservator: Filtering or replacement of oil when ever dielectric strength is unsatisfactory or acidity is beyond permissible limits.2. Tap changer: Filtering or replacement of oil after every one thousand operations of tap changer or whenever dielectric strength is satisfactory or when acidity is beyond permissible limits.

Major Overhaul:The over haul of power transformers has to be conducted as per the periodicity shown below1. 3000kVA Capacity and below 7 years2. Above 3000kVA Capacity -10 years