Research On Multi-target Location Method Of Transformer Partial Discharge Based On Ultrasonic Array Technology

The location of partial discharge sources in power transformers has always been an engineering problem in the field of insulation monitoring of electrical equipment,and so far,it has not been fully and effectively solved.One of the main reasons is that it is difficult to extract effective discharge signals due to the complex insulation structure in the transformer and the harsh surrounding electromagnetic environment.Secondly,most of the current location methods based on time delay estimation are only aimed at the situation of single-point discharge in transformer,However,when the actual partial discharge occurs,many points are often discharged at the same time,which makes the discharge signals received by the sensor prone to aliasing,which leads to the difficulty of time delay extraction and affects the final positioning result.In order to effectively solve the problems of low positioning accuracy and poor fault tolerance of traditional methods under the condition of simultaneous discharge of multiple points inside the transformer,in this paper,the multi-source localization of transformer partial discharge is the research object,and a multi-target localization method of transformer partial discharge based on ultrasonic array technology is proposed.Firstly,based on COMSOL software,the simulation model of ultrasonic propagation characteristics of partial discharge is established,and the time-space distribution characteristics and propagation path law of ultrasonic signal inside transformer are systematically analyzed,an experimental system for studying the propagation characteristics of ultrasonic waves in partial discharge is set up,and the simulation results are further verified.Secondly,the spatial spectrum estimation theory and source number estimation algorithm in array signal processing are deeply studied,and an azimuth estimation method of transformer multiple discharge sources based on improved Geiger circle criterion combined with multiple signal classification algorithm is proposed,and the influence of source number estimation results on the azimuth estimation performance of multiple signal classification algorithm is analyzed.Finally,the multi-platform direction finding cross-location algorithm is used to find out the specific spatial positions of multiple discharge sources.Aiming at the problem that there are false positioning points in this algorithm in the case of multiple discharge sources,a false positioning point elimination method based on the same signal correlation principle is proposed,which can accurately locate the spatial positions of multiple discharge sources.The results show that the ultrasonic signal generated by partial discharge mainly propagates around the transformer in the form of spherical wave front,and the attenuation of this signal is small in transformer oil,but large in winding,iron core and oil tank wall.The estimation result of the number of discharge sources has a great influence on the performance of the MUSIC algorithm’s azimuth estimation:on the premise that the number of discharge sources is estimated correctly,the estimation error of the MUSIC algorithm’s azimuth is less than 1 °,but when the number of signal sources is over-estimated or under-estimated,false peaks and spectral peaks will disappear in the spatial spectrum obtained by the MUSIC algorithm,and the azimuth information of the discharge sources cannot be accurately estimated;The method of eliminating false positioning points based on the same signal correlation principle better solves the problem of false positioning points in multi-platform direction finding cross positioning.The simulation results show that the method proposed in this paper has a good positioning effect,not only can effectively estimate the spatial orientation information of multiple partial discharge sources,but also can further determine their spatial coordinate positions,which provides a theoretical basis for multi-source positioning of transformer partial discharge,and has certain engineering application value.