3D full maxwell research for effect of initial electromagnetic field on very fast transient overvoltage in GIS

Very fast transient overvoltage (VFTO) generated by operating disconnect in gas insulated substations has great concern in high voltage rated substation. Because many effecting factors, including structure parameters and charge distribution, can be integrated into analysis of 3-D electromagnetic finite element method (FEM), this method is regarded as accurate method. VFTOs were analyzed based on electromagnetic FEM method with not only considering the structure of conductors and contacts but also considering the non-uniformity of initial electric field around the conductors at initial time. From simulation results we can see that VFTOs simulated by field based model were larger than that by electromagnetic transient program (EMTP) and the VFTOs by field method advance that by EMTP in time even through ratio of diameter to length is smaller. Comparisons of simulation results were made between circuit-based model and field-based model. The discussions about the key points for the use of field-based model were taken. For larger ratio of diameter to length in compact GIS the magnitude of simulated VFTOs is significantly affected by analysis methods. This field based analysis method will be used in research of phase-selection to suppress the VFTO, in modeling of arcing channel and in obtaining equivalent impedance of source line in GIS.