Study On Identification Of Insulation Defect Of Power Cable Joint

Cross-linked polyethylene(XLPE)cable has replaced other cables,because of its good electrical insulation properties and mechanical properties,it has become the primary choice for laying cables in China.In recent years,state grid corporation has made great efforts to develop the national urban transmission and distribution network,and has used underground power cables to replace the original overhead transmission lines.Power cable line also became the main force of urban transmission and distribution network.Along with the rapid construction and popularization of the cable line,the problems of the stability and safety of the cable line are also concerned.Through a lot of practice,cable joints and the accessories are the most vulnerable parts of cables.At present,the fault of cable joint has been widely concerned in the power industry.Analyze the cause of frequent failure of power cable joint.,to explore the failure mechanism of cable joint,and study through what method to test and assess the running state of cable joint,Measures are taken from the production,construction and operation and maintenance of cables and accessories to reduce the failure rate of cables.To improve the reliability of electric power supply is the most concerned subject of relevant research units and power companies.Through years of experience and research of domestic and foreign scholars,it is shown that the partial discharge of power cable is closely related to its insulation condition.The magnitude of partial discharge is also one of the characteristics of cable insulation which may endanger the safety operation of cable and its operating life.Power cable partial discharge can well reflect the operation of high voltage power cables and the cable joint,it can discover the problems in time,Ensure reliable operation of power cable,This has significant economic and social benefits.Domestic and foreign experts and scholars,IEC,IEEE.As well as international power authorities such as CIGRE,it is agreed that partial discharge test is the best way to evaluate the insulation condition of crosslinked polyethylene power cables.This paper mainly aimed at the unknown condition of the cable defect type corresponding to the partial discharge of power cable.Through the production of cable insulation defects,including: the main insulation surface metal particles,main insulation scratches,joint semi-conducting layer burr cable,it was the three typical defects of the cable.Adopted the constant pressure load cycling test to aging of those cable,through the contrast analysis of pulse current method and high frequency current method two kinds of detection method for various defects cable partial discharge detection.Analyzed the advantages and disadvantages of these two methods.PSCAD/EMTDC software is used to simulate the power cable joint and obtain the partial discharge waveform.The wavelet denoising algorithm based on statistical learning theory is studied.The denoising effect of VCW method and traditional wavelet de-noising method is compared and analyzed.After the denoising work,the characteristic quantity of the corresponding time-frequency domain is extracted for the simulation waveform.The distribution law of various types of partial discharge characteristics of cable joint is studied.