Effect of water vapor on oil-contamination discharge of stator windings

Abstract

It is a common phenomenon for high voltage (HV) motor that bearing bush leaks oil during operation. The oil contamination will etch stator windings and dissolve the ground-wall insulation, make the insulation and wire stratified, reduce the strength of insulation, and finally lead to partial discharge (PD). In addition, water vapor will make the condition worse. Contamination or water vapor covered on the end of stator winding will lead to an intense surface discharge and surface tracking. In this paper, the effects of oil-contamination and water vapor of different relative humidity (RH) on the surface PD taken palce in HV stator windings are discussed. The phase resolved partial discharge (PRPD) patterns were monitored during the aging period. The result confirms that water vapor has a significant impact on the oil contamination discharge. To a certain extent, water vapor can suppress the surface discharge, however, when the RH is higher than 80%, tracking will occur on the surface of the stator windings, and the insulation performance is degraded rapidly. Researching the oil-contamination discharge under different RH will provide a judging basis for the on-line monitoring and fault diagnosis of the 10 kV three-phase asynchronous motors.