Sealed transformer monitoring

Interest in sealed distribution transformers, with and without gas cushions, increased in the 1950s.

byAndrea Tonin, Fiorenzo Stevanato


Interest in sealed distribution transformers, with and without gas cushions [1], increased in the 1950s.

We will talk more about the latter ones, usually used in smaller sizes.

Read the article in PDF

This equipment has found a large market request due to the following reasons:

  • The insulating liquid is protected against the effects of the atmosphere. This allows for keeping the quality of the insulating materials with little or no maintenance.
  • Since a conservator is not required for a hermetically sealed design, this type of transformer has additional advantages arising from the reduced overall height if installed at the wind turbine or application where dimensions are a critical point.
  • Suitable to be filled with natural ester oil (environmentally friendly) with flash point higher than 300 °C.

In hermetically sealed transformers, the oil pressure is usually higher than the atmospheric pressure, and despite conservator-type transformers, the tank of these transformers acts as a pressurized vessel. The tank of hermetically sealed transformers must tolerate a higher pressure. Due to the elimination of the conservator, the oil temperature variations lead to expansion and contraction of the transformer tank. It affects transformer tank design, behaviour, and aging. Transformer tanks are manufactured in corrugated form for efficient heat transfer and oil cooling. The ribs of the corrugated tank have the essential rule in cooling and tolerating pressure variations [2], [3].

 

To read the article, subscribe and choose the option which suits you best. We offer both free and paid options, and the registration takes only a minute.
Subscribe to Transformers Magazine