Degradation of stator insulation of high-voltage asynchronous machines in gamma and neutron radiation field

Abstract

This paper presents the results of an examination of function stability of high-voltage asynchronous motors exposed to ambient strain caused by combined neutron and gamma radiation. This problem appears in practice when a high-voltage asynchronous motor is used in nu- clear power plants where it can be exposed to this type of ambient strain. The failure of the engine's operation under such conditions may have unexpected consequences. As more than 50 % of failure (malfunction) of high-voltage asynchronous motors is caused by damage to stator insulation, the focus of the paper was on testing the effects of combined neutron and gamma radiation on stator insulation. The tests were carried out under well-controlled laboratory conditions on samples taken from both new and used factory coil windings. Two-layer samples were used to record partial discharge threshold voltage and breakdown voltage. By comparing the experimentally obtained results with the applicable mathematical-statistical procedure, an estimate was made of the aging acceleration of stator insulation and the time duration of reliable operation of high-voltage asynchronous motor was determined by life-time exponent.