Experience with post cured insulation systems for large form wound machines

Some 12 years ago the introduction of the Micadur ®-Compact post-cured insulation sysstem led to a complete revision of the insulating process for medium to large high-voltage machines, whose stator windings are built up mainly of form-wound coils. Simultaneously the coil-end supports were completely redesigned, resulting in definite progress being made in respect of the reliability of these machines. This is verified by the operating experience gained from thousands of machines which have already given years of satisfactory service. This article describes the testing methods adapted to suit the modified manufacturing process, refers in detail to the experience gained in operation and indicates possible maintenance tests. The satisfactory experience gained in post-cured impregnation techniques have led to machines being built with ratings up to and exceeding 50 MW.