Partial Discharge Measurement and Condition Monitoring in Power-electronics Controlled Rotating Machines: Issues and Solutions in Advanced Electrified Transport and Aerospace Applications

Going towards efficient speed control of rotating machines, transport electrification, renewables and hybrid grids, power electronics is becoming a major player in generation, transmission distribution and utilization of electrical energy. This paper focuses on electrified transport, including aerospace, where the trend to higher voltage and specific power is leading to the investigation of new designs and materials for electrical insulation. Since insulating organic materials are the most likely candidate, measuring partial discharges, which is the most harmful electrical degradation process, is a must. A new technique for separation of partial discharge pulses from commutation noise is presented, which would work even when switch slew rate is so fast that partial discharge pulses, which occur mostly during voltage commutation transients, are almost totally overlapped, in time and frequency, with switching voltage impulses. Separation of partial discharge pulses from noise allows also identification of the type of defects generating PD to be carried out, which is the basis for condition maintenance. It is shown that the proposed technique can work successfully also to measure partial discharges on-line, during operation of rotating machines, thus constituting a promising tool for condition monitoring of motors and drives developed to fit to advanced electrified traction needs.