Analysis Of Very Fast Transient Overvoltage Considering Residual Charges On Gis Bus

Gas insulated substation(GIS) for its safe and reliable, compact structure, anti-interference ability, long maintenance cycle, etc. have been widely applied to the power system. Therefore, the disconnector switch's operation inside the GIS substation would incite Very Fast Transient Over-voltage(VFTO). VFTO overvoltage has the characteristics of short front time, high frequency and large amplitude, and, its propagation in the system is a serious threat to the safety and stability operation of many primary and secondary equipment operation. In the previous simulation or calculation, bus residual charge's effects on VFTO are obviously. Commonly, it is used in the process of modeling on a capacitance with initial voltage or a current source to simulate the residual charge, this method is simple to carry out, but, in this way, the distribution characteristics of bus residual charge can't be reflected. In order to better to carry out related research, this paper carried out the following aspects of work.First, established each element equivalent model based on 500 kV GIS system in some Hydropower Station, and selected some typical 500 kV GIS system's wiring and operation modes, established the corresponding closing and tripping calculation model and finished the VFTO calculation and comparative analysis.Secondly, in view of the defect that centralized capacitor model can't completely simulate bus residual charge distribution characteristics, in this paper, using the projection method deduced the residual charge density distribution while consider the bus conductor as finite length, established the calculation model of the bus with residual charge distribution characteristics, finished the simulation, calculated VFTO considering the bus residual charge distribution characteristics.Finally, this paper analyzes the effect of support insulator equivalent capacitance, arc resistance, overhead wires length, isolation switch action time several factors' influences of VFTO, The results show that choosing appropriate operation mode and operation time, changing the connection mode of transformer and GIS can effectively reduce the VFTO amplitude.Through the calculation and analysis in this paper, The following conclusions are obtained. First, the harm of VFTO caused by opening operation tends to be more serious than the closing operation. Second,residual charges on the bus distributed uneven very much, the tend of residual charge concentrate to the ends of bus is obvious. Then, it is showed that the residual charge has different effects on different nodes of VFTO in simulation. Last, zinc oxide lightning arrester and resistance installed on disconnector switch has a better inhibitory effect on the VFTO overvoltage. This article not only has important theoretical significance to improve the VFTO calculation model, but also has a certain practical guiding significance of the design and operation of GIS system.