Technology Literature

Three key points for transformer maintenance

1. Installation and operation

Ensure that the load is within the design limits of the transformer. Careful monitoring of the top oil temperature is required in oil-cooled transformers.

The location of the transformer should be adapted to the standards it is designed and constructed. If placed outdoors, make sure the transformer is suitable for outdoor operation.

Protect the transformer from lightning and external damage.

2. Inspection of oil

The dielectric strength of the transformer oil drops sharply as the moisture therein increases. One-tenth of the water in the oil can reduce its dielectric strength by nearly half. Oil samples from all transformers except small distribution transformers should be tested for breakdown frequently to ensure proper moisture detection and removal by filtration.

Analysis of faulty gases in the oil should be performed. Eight kinds of fault gas online monitors in transformer oil are used to continuously measure the content of gas dissolved in oil with the development of faults in the transformer. The type of fault can be determined by analyzing the gas type and content.

The physical properties of the oil should be tested annually to determine its insulation properties. The tests include the dielectric breakdown strength, acidity, interfacial tension, and so on.

3. Regular maintenance

Keep the porcelain casing and insulator clean.

In the oil cooling system, check the radiator for leaks, rust, dirt build-up and any mechanical damage that limits the free flow of oil.

Ensure that the electrical connections are securely fastened.

Check the tap-changer regularly. Also check the fastening, burns, scars, rotational flexibility and contact positioning of the contacts.

Detecting dielectric losses of transformer coils, bushings and arresters every three years.

Check the grounding of the arrester every year. The leads should be as short as possible. Grounding resistance should be measured during the dry season and should not exceed 5 Ω.

The online inspection system should be considered for use on the most critical transformers. There are a variety of online inspection systems on the market, where suppliers assemble different detectors and sensors and connect them to data acquisition devices, while providing the ability to communicate over long distances via modems.

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