Study On Electric Heating Field Simulation And Discharge Test Of Insulation Defects Of Power Cable Joints

The rapid economic growth and the improvement of people's living standards have increased the society's demand for electrical energy.In order to ensure a beautiful urban environment and save land resources,power cables have become very important power equipment in the power system.XLPE cable has excellent performance unmatched by other cables,and is widely used in power systems.The power cable is mainly composed of the cable body,intermediate joints and cable accessories.According to statistics,the main reason for the frequent occurrence of cable accidents is joint failures,accounting for more than 90% of the total failures.The intermediate joint has a complicated structure and is composed of many different materials.It is the weakest component in power cables.According to the analysis of the cause of the joint accident,the failure of the cable joint is due to the defect of the insulation,which leads to the concentration of the field strength,which causes the partial discharge of the insulating material and the breakdown of the insulation.And insulation defects can cause the temperature to rise,causing an explosion accident.These defects mainly come from the factory and the installation site.Insufficient production processes and inadequate installation operations will cause defects in the insulation.These inevitable defects will seriously affect the normal operation of cable joints.Therefore,it is necessary to deepen the research on the insulation defects of the joints to provide an effective basis for maintenance and monitoring.In this thesis,several common joint insulation defects are studied.Firstly,when the main insulation has defects,the distribution of electric field and temperature field are simulated and calculated.The results show that the defects will cause distortion of the field strength at the insulation,resulting in the generation of partial discharges,which in turn will cause insulation breakdown.Defects can also increase the temperature of the insulating material and cause a certain harm to the life of the material.In order to further study the operation of the joint,the interface insulation defects of the cross-linked polyethylene and silicone rubber of the joint were selected for electric field simulation,and the results were consistent with the main insulation simulation.Finally,the interface insulation defects are designed in the laboratory,and the discharge test is carried out.The initial discharge voltage and breakdown voltage when different defects exist in the interface are obtained,the insulation damage after the interface discharge is analyzed,and the correctness of the simulation calculation is verified.Finally,the life model of interface insulation under the combined influence of electric field,temperature field and defects is established,which can provide a theoretical basis for the analysis of cable joint insulation life and has important engineering significance for the monitoring and maintenance of cable joint insulation defects.