Interference analysis and rejection of partial discharge (PD) monitoring signal on-site

According to the waveform and spectrum characteristics, various interferences during on-line PD measurement could be divided into three types such as the sinusoidal continuous noises, pulse shaped interference (including the periodical and stochastical) and background noises (similar to the white noise). Generally speaking, various digital filters could be used to suppress the sinusoidal noise. Some rejection methods for the pulse shaped interference have been developed according to some waveform characteristics and statistical features in the time domain. And the wavelet analysis is a feasible solution to reduce background noises. This paper makes an overall introduction to the anti-interference architecture of a PD monitor and diagnosis system installed in a transformer-generator unit of a power plant in China. Results were also provided in detail of the analysis and rejection for various interferences during on-site PD measurement.