Li Xiuwei

Multi-source separation method for partial discharge detection in substations

Partial discharge monitoring and location system at substation receives radio frequency (RF) signals emitted by partial discharge to position partial discharge using a set of omni-directional RF antenna array. As it is possible for the entire substation to have several partial discharge sources simultaneously, the basic requirement of partial discharge detection at the substation is to judge whether there are multi-source partial discharge signals, and then identify and isolate them. Based on different time domain and frequency characteristics of ultrahigh frequency (UHF) partial discharge signals generated by different partial discharge sources, we perform time-frequency analysis and fuzzy clustering over RF pulse waveforms generated by partial discharge which are continuously acquired and stored, and isolate partial discharge signals from different partial discharge sources or interferences. By this method, we can effectively isolate and accurately position multiple partial discharge sources. Our study lays the foundation for identification of partial discharge types. The feasibility of this method has been proved by field test.

Acoustic-electrical based detection system for partial discharge localization of GIS

A portal acoustic-electrical system for partial discharge localization of GIS is developed, which can be used for multi-channel acoustic-electrical detection of ultrahigh-frequency, ultrahigh-current and ultrasonic signals generated by partial discharge of GIS. The system program, developed based on LabVIEW, is able to continuously capture, sample and store pulse waveforms of partial discharge signals. It can also calculate the phase of discharge pulse, and analyze time-frequency & amplitude-phase distribution of partial discharge signals. By calculating time difference between ultrahigh frequency signals & ultrasonic signals of partial discharge or between ultrahigh frequency signal and ultrasonic signal by multiple-channel detection, this portable acoustic-electrical system can achieve localization of partial discharge. Our system has been applied in partial discharge localization at several 220kV and 500kV GIS substations. The detection results verified the performance of this portable acoustic-electrical detection system.

Adaptive Wavelet de-noising method based on segmented processing technology for PD location

It is possible to carry out PD location using the time difference of PD pulses received by a UHF antenna array. In practical applications, the electromagnetic interference within the substation will pollute these received signals and make it difficult to calculate the time difference of the PD pulses, which, thus, reduces the reliability of the PD source locating. Based on the segmented processing technology, an adaptive Wavelet de-noising method is proposed in this paper. Considering that the level and the time-frequency characteristic of the background noise differ little in microsecond time period of sampling, each waveform acquired by PD detecting system are divided into two sections, the one without PD pulse is used for the calculation of the wavelet coefficients which are used to estimate the de-noising thresholds of the signal. The influence of this adaptive wavelet de-noising process on the PD pulse time delay calculation is analyzed in details. The results of simulation and application show that this method can suppress noise effectively and extract the PD pulse accurately, which contribute to the reliability of the PD source locating.