Performance requirements and test methods for high-voltage a.c.-motor insulation

Tha paper deals with the problems of high-voltage (3¿11 kV) insulation for rotating machines of up to 10¿20 MW. A clear distinction is drawn between the problems of design and the testing of the earth and the interturn insulation. Schering-bridge tests for the quality control of earth insulation above 10kV are advocated. A combination of withstand and breakdown tests at the power frequency are related to system surge levels and the impulse performance of rotating machines in recommendations for earth- and interturn-insulation test procedures in the context of existing specifications for allied apparatus. A brief survey of existing information, particularly on impulse problems, is used to support these recommendations.