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Insulating materials for transformers


Sibel Ltd. is a distributor and agent of the Swiss company Weidmann - world leader in the manufacturing of cellulose-based electrical insulation for oil immersed transformers.

The Weidmann product range includes transformer-board, insulating papers, laminated wood, Krenz fans for transformers, sensors for the presence of gases in the oil, thermal sensors for hot spots in the transformer, lead exits, rings, caps and other machined components.

Oil immersed transformers are designed for operating for decades and the quality of their insulation systems is crucial for longevity.

The life­time of the transformers is directly related to the condition of insulation system.

By laboratory testing of the cellulose fibers of the insulation we can make conclusion about the level of depreciation of the transformer.

The better the cellulose insulation of the oil immersed transformer is, the longer it will be in operation.

The quality of Weidmann materials has been always considered a world standard about cellulose electrical insulation.

The transformer board, as a material for insulation of oil transformers, was invented by  Weidmann in the 30s of XX century.

Weidmann's studies and calculations about the insulating system of oil transformers are the basis of textbooks for students of Electrical Engineering and are desktop books for engineers in design departments around the world.

Even today Weidmann is the undisputed leader in innovation for everything related to the insulation system of oil-filled transformers.

The laboratories and research units WEIDMANN can help you to find the most suitable solution for your transformer.


Here is a brief description of the main materials:

Transformerboard and pressboards - insulation board made of 100% sulphate wood pulp, precompressed (hot pressed) sheet material with high or medium density for insulation in oil transformers LV and HV.

Presspapers - presspaper made of 100% sulphate wood pulp in reels.

Cable paper - the paper is designed for insulation of power cables up to 35 kV inclusive, for insulation of telephone cables, winding wires in oil-filled transformers.

Thermally upgraded paper – paper with elevated heat resistance for applications where a thermal class of 120 ºС is required.

Diamond dotted presspaper (DDP) - electrical insulating presspapers with B-stage resin dots for distribution oil-filled transformers.

WEIDMANN offers special DDP papers with big elongation (up to 20%) and thin thickness, which allows to achieve material savings and speed up the manufacturing.


Crepe paper – for application when wrapping of products with complex and irregular shapes is required.

Adhesive tapes for oil transformers - the full range of adhesive tapes used for the production of oil and dry transformers.

Glass banding tape - suitable for reinforcing tape for banding coils in dry and oil transformers.

Nomex paper – a trademark of  Dupont  for a special aramid paper. It has good electrical and mechanical properties and exceptional heat resistance - class 180 ºC.

Transformer Laminated Wood – class CR2 on sheets of different thicknesses.

Casein-based glue for oil transformers - used for gluing cellulose insulation materials. Compatible with different types of transformer oils.


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