Research On On-line Monitoring Technology For Insulation Aging Of XLPE Cable

XLPE cable is widely used in various transmission lines because of its good insulation,electrical and heat resistance,mechanical properties and low dielectric loss.Influenced by different conditions,the insulation aging phenomenon will occur during the operation of the cable,resulting in the decline of the insulation performance of the cable,leading to the breakdown of the insulation layer of the cable,leading to cable accidents,reducing the service life of the cable and power supply reliability of the grid.Traditional fault detection is mostly off-line detection,which can not meet the needs of contemporary social development.Therefore,through on-line monitoring and identification of the insulation performance of the cable,the cable defects are found,the possible faults are warned,and the predictive maintenance system is established,which is of great significance to ensure the reliability of the power grid and improve the quality of power supply.In this paper,the causes of cable insulation aging and the main monitoring methods of cable insulation are analyzed.It is considered that the insulation aging of cable can be judged and the insulation performance of cable can be evaluated by monitoring partial discharge signals.Firstly,the equivalent circuit model of air gap partial discharge is established,and on this basis,the air gap discharge simulation model of cable insulation dielectric based on MATLAB/simulink is built.The partial discharge signal is denoised by wavelet transform.The PRPD statistical operator is used to construct the characteristic vector of partial discharge for support vector machine,and the support vector machine is used to recognize the partial discharge signal.In the process of recognition,the principal component analysis method is used to reduce the dimension of the characteristics of partial discharge vectors,and GWO is used to optimize the parameters of support vector machine,which improves the accuracy of partial discharge signal recognition.Finally,a fuzzy comprehensive evaluation method based on monitoring partial discharge signals of cable insulation dielectrics and supplemented by cable surface temperature and DC leakage current is proposed.The signal acquisition and processing circuit and the system scheme of on-line monitoring and evaluation of cable insulation performance are also designed.In this paper,the on-line monitoring method of XLPE cable insulation performance is studied in depth,and a new method based on partial discharge(PD)signal characteristics and the fuzzy comprehensive evaluation method of cable temperature and DC leakage current is proposed to evaluate the cable insulation performance.The feasibility scheme of cable on-line monitoring and insulation status evaluation is put forward for the evaluation of cable insulation performance in various operating environments.It provides a theoretical basis for cable insulation monitoring based on partial discharge signal.The paper has 43 figures,8 tables and 60 references.