Analysis And Research On Electrothermal Coupling Characteristics And Fault Of 35kV Power Cable

In this paper,35 k V three core AC power cable is taken as the research object,and the two-dimensional simulation model of cable is built in the finite element software.By analyzing the physical process of electric field and temperature field of cable,considering the dynamic parameters of materials,the coupling model of electric and thermal physical field of AC cable is constructed.The law of cable temperature field changing with conductor current and buried depth is simulated and analyzed;According to the corresponding relationship between dielectric parameters and temperature distribution of insulation materials,the electric field distribution of cable insulation layer is calculated,the influence of environmental parameters and current carrying capacity on the electric field distribution and the influence law of voltage on temperature field are analyzed,and the accuracy of the model is verified.In the aspect of cable over-voltage characteristics and fault,the system simulation software is used to build a simulation model to study the power frequency voltage rise caused by no-load capacitance effect and asymmetric short circuit,and the switching over-voltage characteristics caused by no-load line closing and opening.Therefore,by analyzing the characteristics of typical overvoltage waveform,it is found that when single-phase short circuit occurs,the non fault phase voltage increases by 1.52 times,the short-circuit current increases significantly,and the switching overvoltage may increase by 2.2 times.These overvoltage characteristics affect the safe operation of the cable,and may cause cable failure and insulation aging.According to the influence of impurities in the cable insulation,combined with the electric thermal coupling model,the influence of insulation aging parameters and impurity types on the electric field and temperature field of the cable is analyzed;It is found that with the development of thermal aging,the temperature distribution of cable increases as a whole,and the electric field distortion caused by impurities is obvious.The size,location and dielectric parameters of impurities will affect the electric field distribution.