Reliability and Testing of High-Voltage Stator Insulation for Large Rotating Machines

Stator insulation with mica splittings, vacuum impregnated with epoxy resin, originally introduced by Siemens in 1958 and successfully applied to 21 kV generator stator windings since 1963, is today being used with all steam turbine generators being built by Kraftwerk Union and Allis-Chalmers Power Systems. The method of manufacture and the development research, which led to this insulation system, known as Micalastic ®, and the tests which have been continuously carried out for evaluation and production control purposes are described in this paper. Micalastic insulation has proven itself in the faultless operation of numerous large generators.