Low-frequency drying

As part of our transformer maintenance service, we perform desiccation based on low-frequency heating in combination with filtration and regeneration of transformer oil. 

Application of low-frequency sources for drying of oil transformer solid insulations

During the operation of oil transformers in the electricity distribution network, the insulation system becomes damp as an unwanted effect of the air humidity and temperature changes of the transformer.

Humidity (water) in the insulation system of an oil transformer is unpleasant because of two reasons:

  1. it lowers the electrical solidity of the insulation
  2. it is the source of oxygen, which oxidizes the insulation system and thus shortening its durability

Solid insulations are a significant water reservoir. The principle of eliminating the water from these insulation lies in their heating using a special low-frequency source.

 The mobile LFHE II device (Low Frequency Heating) on a trailer cart for automobiles.

In the use of this source, the heat is supplied from the transformer winding to insulations, structures and barriers. The regenerating device then sustains the appropriate temperature cadences in collaboration with this source and collects the humidity ejected from the solid insulations from the oil. The insulation system stays in its natural environment under the oil.  


The collaboration of the LHFE II device with the station for the regeneration of transformer oils.

This method of transformer heating and drying increases the efficiency and shortens the currently used procedure for heating the transformer, which only uses the circulation of insulation oil and oil insulation. A big advantage is, that we can dry the transformer directly in its place. This kind of drying cuts down on the expenses for dissassembly, transportation, eliminating the unpleasant vibrations to the transformer and its insulations during transport. At the same time, from an ecological point of view, pumping, transportation and storing of the oil is also eliminated. 

Detailed informations are in the brochure Use of low-frequency sources for the drying of solid insulations of oil transformers (PDF, 3,2 MB).

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Contact us

Low-frequency drying

Michal Sláma, trafa(at)revos.cz
(+420) 725 878 688