ELANTAS Electrical Insulation

Application of epoxy resin on cast resin transformer

Presenter:   Dr. Franco Marini
Company:SIM S.r.l.
Title:Managing Director


Cast Resin Transformers are nowadays the most common technology in the field of distribution transformer, both for standard and special applications. Reasons for this trend are many, and almost all of them are connected to the solid and fire resistant insulating system, giving a lot of advantages in terms of maintenance, safety, place of installation, transformer dimensions and weight and so on.
Of course, to get all the advantages that this technology offers and use it properly, it is necessary to choose the right Epoxy Resin according to the application, used conductor materials, installation site and working temperature as well as a good design.
Installation site is one of the most important things to keep in account: if outdoor or indoor (Epoxy or Cycloalifatic compounds), if the installation site is a very hot place or a very cold place (Climatic Class C), if there is a consistent condensation or not (Environmental Class E), if the risk of fire is high or low (Fire Behavior Class F).
As for all solid insulating materials, working temperature is really important because it defines the life time of the insulating system and, therefore, of the transformer. Thermal insulation classes used for Cast Resin Transformers are almost two, F (155 °C) and H (180 °C) class.
Finally, but not for order of relevance, conductor material used for windings slightly change the mix of Resin Compound because Aluminum and Copper have a quite different thermal expansion coefficient, and the insulating system have to be able to follow thermal expansions evolution in the temperature operative range without creating any crakes on the cast coils.