Aging properties of mica insulation systems impregnated with solventless resin for generator stator coils

As stated in the above, the non-destructive test with solventless coil having been kept in operation for approximately 10 years showed some changes in the electrical properties, but the breakdown voltage remained unchanged. When the electrical properties of solventless coil was compared with those of asphalt coil obtained form the literature, the solventless coil was proved to be thermally stable, less hydroscopic, its electrical properties being less affected by aging. In the recent coils, the impregnated resin and the mica tape have been improved, permitting one to expect more stable performance.