Partial discharge detection technology on inverter-fed motor insulation

To extract signals for partial discharge (PD) detection in inverter-fed motors under square voltage pulses that have short rise/fall times, we compared the PD pulses obtained by ultra-high frequency (UHF) tests using high frequency current sensor and disturbance from pulse generator in aspects of their time- and frequency-domain features. According to the different characteristics of the two types of pulses, we proposed a processing method which could suppress disturbance and improve the signal to noise ratio (S/N). The analyses indicate that, in the process of detecting PD on inverter-fed motors performed according to IEC standards, the UHF method is preferred for its excellent S/N. The correction analysis can be considered as a useful method for determining overlapping of the PD and disturbance pulses. Meanwhile, high frequency current test can also be used as a supplement to the UHF method, resorting to correlation coefficient and sym2 wavelet extraction technology.