Study On Partial Discharge Location Of Long Distance Cable Line

Cable is an important part of power system,its state is related to the stable operation of power grid.But because the cable is usually buried underground,its state has strong concealment.Previously,the electric power department adopted the operation strategy of preventive periodic maintenance or after-event maintenance,but with the development of social economy and power system,the cable lines expanded rapidly.Traditional maintenance methods are increasingly unable to meet the requirements of continuous and reliable operation of power lines.How to ensure the reliability of power supply under the limited human and material resources is an urgent problem for the power sector.Compared with traditional maintenance,condition detection can understand the operation of equipment in real time,and carry out targeted maintenance based on the test results.By comparison,partial discharge method is used to detect insulation defects of cables.In view of the low discharge and high noise in partial discharge of cables,the mechanism of partial discharge of cables is described in this paper.Then,the different state components produced in partial discharge process are compared,and the electrical signal and acoustic signal are used as the detection objects to complement each other.The mathematical model is constructed and the characteristics of electrical and acoustic signals in cable propagation during partial discharge are analyzed.This paper analyses the properties of common interference in the detection field,adds noise to the signal according to the noise in the field,and uses wavelet transform to denoise the noise-added signal.By comparing the characteristics of the partial discharge signal,Sym8 wavelet basis and hard threshold method are adopted.Although the filtered signal has obvious distortion,the method of hard threshold is adopted.However,the overall characteristics have not changed.The time delay of the filtered signal can be obtained by using the generalized correlation method.Finally,the simulation model of cable partial discharge is built through simulink.The results show that due to the attenuation and dispersion effect of electrical signals in the transmission process of cables,it is difficult to achieve an ideal positioning effect.Generally,this method can only be used for preliminary positioning.The insulation defects can be accurately located by the prior positioning results of electrical signals and then by ultrasonic positioning.In this paper,the positioning accuracy of Chan algorithm is tested by changing the number of sensors and the error of time delay.The results show that the positioning accuracy can be improved by using high sensitive ultrasonic sensors and increasing the number of sensors appropriately.