A Fast Calculation Method of Electric Field Distribution for HVDC GIL Based on Equivalent Gas Conductivity

With the development of power system, the capacity of power grids has increasing quickly. Technologies for gas-insulated metal-enclosed transmission line (GIL) under high voltage direct current (HVDC) voltage have also begun the research field concerned by scholars. The migration and diffusion equation of weakly ionized gas is deemed to be an accurately calculating method for the electric field of HVDC GIL at present, by considering the charge accumulation. However, the large amount of calculation and the poor convergence will take up a lot of time, which make this method not suitable for the structure optimization with intelligent optimization algorithm. On the other hand, because the gas conductivity of SF6 can't be measured exactly, constant current field calculation may cause large error. Therefore, in this paper, an equivalent gas conductivity method was proposed. The finite element model of basin insulation for HVDC GIL was built and the electric filed was calculated by the method of weakly ionized gas, which considered the law between conductivity and temperature of epoxy composite. In constant current field, a series of electric filed calculated by changing gas conductivity. To judge if the results of different methods have the same effect, electric potential curves of basin insulator surface in different methods would be compared. The result shows that the closest one to the electric filed distribution calculated by the method of weakly ionized gas can be selected to set the gas conductivity. In this case the field distribution of two methods was basically the same. The method of equivalent gas conductivity has achieved the function of fast calculation, and provided valuable references and calculation time reduced for the design of HVDC GIL