Partial discharges analysis of electrical machine winding in low pressure enviroment

Breakdown voltage of gas insulation depends on its pressure as is described by Paschen’s curve. Therefore, usage of various electrical devices at high altitudes can lead to insulation breakdown if it is not properly designed for this environment. The accompanying phenomenon of imminent insulation breakdown is presence of partial discharges. This paper describes influence of air pressure and temperature on partial discharge activity. The monitored parameters were inception voltage, number, and amplitude of pulses at constant voltage at various air pressures and temperatures. Measurements were conducted on stator winding of electrical machine in vacuum chamber specially designed for high voltage measurements.