Calculation Model of VFTO Considering Transmitting Characteristics of GIS Enclosure

The exact transient circuit model of gas insulated switchgear (GIS) can directly affect the accuracy of very fast transient overvoltage (VFTO) results in case of calculation.Taking a 1 100 kV GIS substation in China as example,a model symbolizing the transmitting characteristics of GIS enclosure is formed on the basis of theory of multi-conductor transmission lines and phase-model transformation method.By combining above model with the internal transient circuit model of GIS,the VFTO produced by operation of disconnector is calculated and analyzed in details such as the maximum value,spectrum characteristics and rising rate of VFTO on the principal devices inside GIS.Besides,the effect of residual voltage on unoperated phase bus on VFTO of operated phase is also discussed.The calculation and research results could be used as reference for electrical design of GIS and those electric devices connected with it.