Recommended Practice for the Evaluation of the Impulse Voltage Capability of Insulation Systems for AC Electric Machinery Employing Form-Wound Stator Coils
Scope and Purpose This recommended practice outlines test procedure for the evaluation of the impulse voltage capability of insulation systems of form-wound alternating current rotating electrical machinery. This test procedure forms a base for the accumulation@ analysis@ and reporting of information concerning impulse voltaee withstand strength of around and turn insulation@ both new and aged. The immediate goal is a better understanding of relevant aging mechanisms: the ultimate aim of this document is to aid in estimating life of an insulation system under specified service conditions. It must be emphasized that this test procedure is intended@ at this time@ for trial use. Future revisions@ made after experience with it@ should result in more definitive specifications being possible. This procedure recommends the use of multi-factor aging@ tests@ combining thermal and electrical aging in order to address the withstand capability of micaceous insulation. Variations of this procedure may be tried@ such as for voltage ratings other than 6.9 kV and 13.8 kV for turn insulations other than mica. and for various impulse wave forms. The procedure is primarily directed toward providing a qualification test for the turn insulation in regard to its ability to withstand impulses that might be impressed on the terminals of a machine and that result from switching surges@ lightning.@ or other disturbances. It will also provide information on the ability of the ground insulation to withstand impulses. In addition@ the test model used in the tests described hereimi will be suitable for testing the strand insulation. if that is desired@ althoug.h it is not a ftmnctioii of this qualification test procedure.