Effects of vapor with different chemical properties on corona partial discharges of stator windings

The effects of vapor with different chemical properties on corona partial discharges (PDs) at the junction section of the semi-conductive tape and the stress grading tape of stator windings were investigated. The phase resolved partial discharge (PRPD) patterns were collected during the experiment to obtain the characteristics of the PDs. The result has confirmed that relative humidity (RH) of the vapor with different chemical properties can cause corona discharge to change significantly. The acidic vapor can suppress corona discharge effectively. When RH exceeds 60%, the corona discharge would be hardly induced even though the voltage is boosted up to twice the operating voltage. When RH is over 80%, corona discharge will develop into phenomenon of creeping on the surface of the ground wall insulation and can hardly be collected through the capacitive coupler.