Analysis Of Cable Terminal Fault Characteristics Based On Electric-thermal Field Simulation And Optimization Studies

As the demand for power supply reliability in various industries continues to increase,cables,as an integral part of transmission and distribution systems,are increasingly demanding safe and reliable operation.The cable terminal is an important connection device between the electrical equipment and the transmission and distribution network,and it is also a weak link in the safety performance of the entire transmission and distribution system.Generally,The cable terminal needs to be installed and prepared on site.Various defects are introduced,leading to frequent failures,ranging from reduced power supply quality to severe breakdown explosions,damage to cables and equipment along the route,resulting in power outages in large areas and major economic losses.Therefore,in view of the particularity of the cable terminal,through the finite element simulation software,it is of great significance to explore the electric and thermal field distribution characteristics of the terminal with various faults and defects,and to propose an optimization plan to improve the terminal’s electric and thermal field distribution and improve its insulation performance.Firstly,this article dissects the on-board 25 k V ethylene-propylene rubber cable terminal and the distribution network 10 k V cross-linked polyethylene cable terminal according to the on-site operation situation,to understand the internal structure of the two types of cable terminals,and builds two types of cable terminals Finite element simulation model under normal conditions and with defects.Secondly,the numerical coupling calculation model of the electric heating field of the cable terminal under different operating conditions is studied.Based on the finite element simulation analysis,the electric heating field distribution of the two types of cable terminals under normal conditions and various types of defects is calculated.The simulation results show that the vehicle The electric field of the 25 k V ethylene-propylene rubber cable terminal is slightly distorted at the cut-off point under normal operation,and in the case of scratched air gap defects and metal particles,the electric field strength at the cut-off point is greater than the air breakdown field strength,and the temperature at the defect is abnormal,these Will accelerate the deterioration of the material at the defect.And the distribution network cable terminal uses the geometry of the stress cone to conduct a uniform electric field,but in the case of air gap scratches and metal particles,the outer semiconductor layer is cut off and the stress cone is turned.All the electric fields in the field are distorted and the temperature rise is abnormal.With these defects,the cable terminal of the distribution network will be difficult to operate safely for a long time.Finally,according to the specificity of the electric field distribution of the two types of cable terminals,an optimization scheme is proposed and verified by experiments:Among them,for vehicle-mounted cable terminals,it is proposed to optimize the electric heat field distribution through the optimization of the outer semi-conductive layer chamfering,the size of the heat shrinkable tube,and the use of non-linear stress tubes.At the same time,according to the optimization plan,the cable terminals before and after optimization are made to perform partial discharge Testing experiments,infrared thermal imaging testing experiments and voltage breakdown experiments,the results show that the insulation performance of the optimized cable terminal has been effectively improved.For the cable terminal of the distribution network,the chamfer optimization of the outer semi-conductive layer,the optimization of the size of the outer semi-conductive layer,and the optimization of the stress cone insulation material are proposed.And through finite element simulation calculations,the results show that the optimized cable terminal contains various defects in the case of The distortion of the electric field has been effectively reduced,the maximum value of the electric field strength is lower than the critical breakdown field strength,and the abnormal temperature rise has decreased.At the same time,the effectiveness of the optimization scheme has been verified by partial discharge detection experiments,infrared thermal image detection experiments,and voltage breakdown experiments.The results show that the partial discharge distribution and surface distribution trend of the cable terminals before and after optimization are the same,but the partial discharge activity is effectively suppressed after the optimization scheme is used,the surface temperature is abnormally reduced,and the voltage breakdown effect is more durable.