Enhanced compressive creep performance of high voltage insulation

The groundwall insulation system for generator and motor high voltage coils is typically constructed with mica paper tape and impregnated with either an epoxy or polyester resin. The coil end turns are of the same insulation system as the coil straight part, but the end turns are usually subject to much higher compressive forces. These compressive forces usually result from end turn bracing components, during coil installation, and possibly during abnormal operating conditions such as a sudden three phase short circuit. These high compressive forces can lead to significant groundwall insulation damage if the compressive force capabilities of the insulation system is exceeded. Without changing the components or processing of the basic groundwall, which have been designed to meet rigid dielectric and mechanical performance requirements; a method to increase the compressive creep capabilities of the insulation system has been developed and tested at compressive loads of 5000 psi. The development, testing and the description of the enhanced compressive creep groundwall insulation is presented in this paper