Evaluation of Medium Voltage Stator Bar Groundwall Insulation under Inverter-Fed Pulses

In this research work, the behavior of medium voltage stator bar groundwall insulation that is subjected to steep-front voltage pulses, at various repetition rates and temperatures, is studied. The test conditions include; pulse voltage amplitudes up to 3.5 kV_p, pulse switching frequencies up to 3 kHz, and in ambient temperatures of 23 and 155 degC. During the aging process, the surface temperature is monitored with an infrared camera as a means for determining the locations of the highest temperature and therefore the highest regions of PD activity. Visual observations confirm degradation of the groundwall insulation in the regions of highest temperature and PD measurements show increased activity and reduced PD inception with aging.