Study On Multi-object Localization Method Of Partial Discharge In Transformer

Power transformer is one of the important electrical equipments.The safety and stability of power system are closely related to the operation state of transformer.In the fault statistics of transformer,the decline of the performance of its internal insulation material occupies a large proportion,and the main factor affecting the insulation condition is partial discharge.Partial discharge(pd)will inevitably occur in the long-term operation of transformer,and the location of pd has a great influence on the evaluation of insulation performance.Therefore,it is of great significance to study the localization of partial discharge.When partial discharge occurs in transformer,ultrasonic and ultra-high frequency signals will be generated.In this paper,the partial discharge point is regarded as the emission source of the two signals according to this characteristic,and the distance and azimuth are calculated and estimated to determine the specific location of the discharge point.The main contents of this paper are as follows:(1)this paper introduces the research background and significance of this paper,introduces the research status of domestic and foreign countries through the main methods of partial discharge positioning,and analyzes the advantages and disadvantages of these methods.(2)the generation,hazards and classification of transformer partial discharge are introduced,and the array signal processing technology is summarized.The direction of arrival estimation is introduced in detail.According to the requirements of this paper,the orientation matrix of L-shaped and planar sensors is analyzed.(3)analyze the difference between single-channel denoising and multi-channel denoising of partial discharge,and use CFastICA algorithm to denoise the array signals,which is beneficial to retain the phase difference information in the array signals and the complex matrix in it.The waveform characteristics of the ultrasonic signal were basically restored,and the similarity coefficient,the trend coefficient of the waveform variation,and the phase angle difference of the array flow pattern were used to evaluate the denoising performance,indicating that the denoising effect is good.(4)the principle of classical MUSIC and its improvement scheme are expounded.The improved MUSIC algorithm is applied to the direction finding of narrow-band signals.Thesimulation results show that the direction finding effect has been significantly improved,and the coherent signals can be effectively identified.Due to partial discharge when the ultrasonic signal is a broadband signals,thus before direction finding,adopted the focus of TCT algorithm will be focused to a reference frequency signal,and then the improved MUSIC algorithm is applied to the signal direction finding,and do the simulation test,the results show that the method can effectively detect the orientation of the broadband signal information,the final basic direction-finding error between 1° ~ 2°.(5)introduce the number identification method of narrow-band and wide-band signal sources,calculate the distance information by using the time delay of uhf signal and ultrasonic signal,and realize the positioning of local source by combining with the azimuth information,with the positioning error within 4cm.