CSS sahara_02_04_instructions.doc
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connections. It is essential that electrical connections be made properly to prevent and reduce
overheating.
3.
Mechanical Operation
During routine tests, mechanical operation of the circuit protective devices or disconnects should
be checked by turning it "ON" and "OFF" at least three times.
TRANSFORMER MAINTENANCE
Inspection during operation
1. Inspection of oil level: when adding oil safety distances have to be observed.
2. Inspection of oil leakage.
3. Inspection of transformer surroundings.
4. Inspection of surface treatment.
Maintenance during operation
For personal safety reasons only a limited amount of maintenance activities can be performed on
the transformer when it is in operation. These activities are, however, possible if safety
regulations are followed. In practice, however, always safest to remain below the level of the
cover of the transformer. Maintenance activity, which can be performed during operation is oil
sampling only.
Inspection and Measures to be taken during downtime
During downtime all inspection work and maintenance measures can be carried out, which can not
normally be performed during operation.
Before starting maintenance work, the transformer has to be disconnected from the network and earthed
or grounded. When the disconnector has been opened, one has to see to that they stay open and, before
grounding or earthing, one has to test that they are voltage free, i.e., with a voltage tester.
Inspection of oil leaks and precautions to be taken.
Oil leaks may occur as follows:
1) From bushing gaskets (if the gasket has become loose, tightening will help; if the gasket has lost
its elasticity, it has to be replaced. The reason for losing the elasticity can be excessive heating
or ageing of the gasket).
2) From cover gaskets, valves, and gaskets of the off-load tap changer (tightening of the screws or
bolts will usually help).
3) From welded joints (leaking joints can be repaired by welding. A skilled welder is needed for
the job).
Cleaning to be carried out annually:
1) Bushings (cleaning agent e.g. white spirit)
2) Transformer cover and tank
3) Glasses of relay, thermometer, and oil level indicator
Surface treatment:
Surfaces that have not been inspected during operation, should be checked and
the
damage
coatings be repaired.
Inspection and maintenance for accessories, protective and regulating equipment:
