Development of thermalastic epoxy for large high voltage generators

During the last fifteen years, the emphasis in stator insulation for central station generators has shifted from electrical to physical properties. To meet this requirement change, the Westinghouse Thermalastic Epoxy insulation system was developed, in which the previously used polyester resins were replaced with epoxy resins. The improved physical properties of this new resin system resulted in a mechanically stronger coil insulation. The insulation was also found to be able to better withstand thermal cycling forces, reflecting both its improved mechanical and thermal characteristics. In addition, its superior resistance to water diffusion ïndicated a great safety margin in the unlikely case of internal leaks in water-cooled windings.