Research On The Evaluation Method Of Power Cable Insulation Status Based On Short Circuit Response Measurement

Thermal aging and water tree aging are the important reasons for the degradation of insulation electrical performance of XLPE cables and the occurrence of cable faults.Timely detection and treatment of these two aging defects are of great significance to the safe and stable operation of the power system.In order to address the current difficulties in detecting thermal aging and water tree aging in engineering applications,a method for evaluating the insulation status of power cables based on short-circuit response measurement is proposed.By measuring the short-circuit response voltage waveform of cables under different DC charging voltages,the DTFT method was used to obtain the Ⅰ and Ⅱcharacteristic spectra,and relevant feature quantities were extracted to achieve the evaluation of the insulation status of power cables.By fitting the branch parameters of the extended Debye model,the relationship between the eigenvalues and the branches of the extended Debye model is analyzed.Conducted overall and local aging tests on short and long cables,analyzed the impact of cable length on defect characteristics,and proposed criteria for overall and local aging of cables.Based on the short circuit response voltage waveform,an extended Debye model fitting system was built,and insulation assessment maps of different aging models were drawn.The research results show that:the short-circuit response method can realize the detection and type distinction of cable aging,and it is easy to detect,has low requirements on the experimental environment and detection equipment,and has great potential for engineering applications;The characteristic spectrum characteristics,nonlinear aging characteristics,voltage characteristics and extreme frequency point characteristics all change regularly with the water tree aging and thermal aging,which can diagnose the overall aging defects of the cable;in the local aging of the cable,the Ⅰ and Ⅱ characteristics The spectrum can effectively identify water tree aging and thermal aging defects,and the type Ⅱ characteristic spectrum has strong sensitivity;the short-circuit response measurement method based on the extended Debye model fitting system can effectively analyze the polarization characteristics and circuit parameters And diagnose cable aging defects,and has the potential to diagnose other insulation media.