Corrective Maintenance of Oil-Filled Transformers

Corrective Maintenance

Corrective maintenance of oil transformer is performed according to mandatory schedule and according to the current condition of the transformer.

Corrective maintenance includes certain measures, such as external inspection and repairs, cleaning of insulators, radiators and the tank, removal of dirt from the expansion tank, adding oil, sampling of oil and making all the necessary measurements and tests.

The first thing to pay attention during repairs is the tightness of seals. If any problems are detected, nuts must be tightened. However, this does not always stop oil leaks. If this is the case, it is recommended to change seals.

The tank and the radiators of the transformer must be cleaned from dust and dirt, and the insulators should be wiped with petrol. If the oil level is incorrect, add oil. This can be done using GlobeCore’s UVD units. The product is designed to add degassed transformer oil to high voltage oil filled airtight ports of transformers and switches. It can be used in power plants, substations and other electrical facilities.

If the indicator silica gel is pink, it must be changed. Used silica gel can be restored by drying.

Acid number of the oil indicates the need to recharge the dehydrating filter breather. If this parameter reaches 0.1 mg KOH/g, it is time to act. Oil is drained from the expansion tank, then the lid and the silica gel are removed. Old silica gel is replaced with new. After setting the lid back on the transformer, oil is added to the expansion tank, but only after releasing air from the filter.

Corrective maintenance of dry transformers includes removal of the casing and checking all components for mechanical damage. Grounding and contacts are checked. Transformer is purged with hot air and insulators are wiped. Then check impedance of winding insulation.