By establishing inner and outer models of GIS in transient state based on the theory of multi-conductor transmission lines and the phase-model transformation method

the transient enclosure voltages（TEV） on each earthing point of GIS were calculated for the disconnector’s operations of closing/opening the short bus according to a 500 kV GIS substation.The waveforms and spectrums of TEV on each earthing point on the enclosure were obtained.In addition

the effect of the number of earthing lead on TEV was investigated.The results demonstrate that TEV has the characteristics of sharp steepness

high amplitude

and multiple frequency components

and whose maximum value always appears on the earthing point of operation phase out-line bushing.Moreover

adding earthing leads of the same point can decline the amplitude of TEV significantly.