Research On The Surface Electric Field Performance And The Flashover Model Of Ice-covered HV Insulators

Due to the varied topography and large icing area in China, the flashover accidents of ice-covered insulators happen with high frequency. With the implement of the West-to-East Power Tranmision, South-and-North Power Transaction and Nationwide Electricity Interconnection strategy and the construction of the UHV AC and DC Transmission Lines, it is inevitable that the EHV and UHV transmission lines cross the areas of icing, high altitude and contamination, etc. Operation statistics and researches at home and abroad show that the degradation of the electrical performance of the insulators caused by icing is one of the important causes for power outage accidents. Because there are many factors affecting the icing of insulators and their discharge process is more complex than that of polluted insulators, researches on the discharge mechanism of ice-covered insulators, which is still in the experimental stage, is left behind those on the discharge characteristics.Based on the researches on the ice-covered insulator at home and abroad, this dissertation expatiates on the numerical analysis method of electric field along the ice-covered insulator and builds the finite element surface electric field calculation model of the ice-covered DC and AC insulators with various icing type. The Asymptotic Boundary Conditions (ABC) and the virtual material characteristics methods are employed to solve the problem of open boundary and floating conductors. With the electric field calculation model, the influence mechanism of air gap, icing as well as sheds configuration on the surface electric field performance of ice-covered insulators is studied in this dissertation. The surface electric field performance of ice-covered composite insulator is compared with that of the ice-covered ceramic insulator string. Based on this comparison, the optimal method of the sheds configuration is puts forward.Moreover, this dissertation puts forward the dynamical physical-mathematical DC and AC flashover model of ice-covered insulator based on the electric field calculation model for the first time. The flashover process of the ice-covered insulator is divided into three stages in this new flashover model, which are the arc initiation before air gap breakdown, the arc propagation after air gap breakdown and the flashover determination. The different electric field calculation models of the first two stages are built separately. With the E-I characteristics of DC and AC arc of ice-covered insulator, this model can dynamically predict the leakage current and the flashover voltage of...