Objective of Maintenance
To achieve the maximum availability of this Service in the power system, standard procedures of transformer maintenance should be carried out on each piece of equipment installed in the switchyard. The frequency and extent of such supervision and control are dependent on climate, environment, service conditions, etc.
This results in
- The equipment lasts through its life period, thus avoiding a blow to the growing economy
- Avoid the breakdowns resulting in more expenditures.
- Decrease shut-down time, so that the facility from the equipment is available as long as possible.
- Avoid loss of energy.
STRESSES that reduce the life in power transformer
- Mechanical
2. Electrical
3. Thermal
4. Chemical
5. Magnetic
Maintenance Schedule of Transformer
- Daily -(Noting ambient.Temp. Winding. Temp.Oil temp. and Load amps, Voltage & taking remedial measures if found difference.
- Monthly maintenance-(Noting Oil level in Transformer. & bushing, Leakage in the radiator, Dehydrating breather De-aeration in Bushings, Bucholz relay, OLTC\ diverter, etc.)
- Quarterly maintenance-(Cooler fan bearings, motors, and operating mechanisms Radiator Oil filled bushings. gasket joints.)
- Half-yearly maintenance -Cable boxes Surge diverter and gaps Relays, alarms their circuits etc
- 5\10 yearly maintenance -Overhaul inspection including the lifting of core and coils etc.
Details of Monthly Maintenance-
Before starting the maintenance work careful attention should be given to shutting down and getting line clear permit of the transformer.The steps are as follows
- Disconnect loads first.
- After disconnecting loads, you can disconnect the source.
- Circuit breakers opened first, then isolators (disconnectors).
- Discharge rods are connected on both side
Checklist
- Checking the transformer supports and transformer level.
- Tightening of all connections.
- Check for load during peak load time. If overloaded, transfer loads to the adjacent transformer or provide an additional transformer.
- Check for leakage of oil in drain valves, tank, conservator, etc., prevent leakage and top up the oil level.
- Check the bushings for chipping and broken porcelain.
- Check the arcing horns for proper alignment and gap and for any damages due to flash-over.
- Check for breather opening and color of silica gel. Recondition silica gel if necessary.
- Check the earthing conductor for its size, tight and intact status.
- Check the danger plate for its support, height, and facing in the right direction.
- If provided with an explosion vent check the diaphragm for cracks or broken condition.
- Check for general cleanliness, tightness of all bolts and nuts, etc.
- Check the lightning arresters for line and earth connections, flashovers, and broken or damaged porcelain.
Summary
The objectives of transformer maintenance can be achieved with close health monitoring by adopting state-of-the-art techniques/tools and taking necessary remedial measures, maximization of service life can be attained by carrying out refurbishment at the right time. All maintenance test results and observations should be specifically recorded for future reference.
