Bus container 1 of cylindrical shape is filled with insulating gas and main circuit conductor 2 is housed with bus container 1 in taut condition. Bus container 1 has flange 3. Current transformer container 4 is installed adjacently to bus container 1. Current transformer container 4 includes inner cylinder 5 and outer sealing member 6. On the periphery of inner cylinder 5, three current transformers 11 are provided interposing insulative cushioning material 10. Other longitudinal end of inner cylinder 5 and bus container 1 are arranged so that insulation gap 9 is formed in between. Between inner cylinder 5 and outer sealing member 6 on insulation gap 9 side, varistor 15 of which resistance varies depending on a applied voltage is electrically connected through bonding conductor 16. Varistor 15 turns into a conducting state when a surge voltage over a predetermined intensity is applied.