Abstract: Bushing leader circuits 3, 4 are connected to end portions of two main buses 1, 2 on the side of a leading-in steel tower 110, and cable head units 85, 95 of cable leader circuits 6, 7 connected to the main buses 1, 2 are arranged in a space formed between the main buses 1 and 2. Thereby it is possible to achive both of simplification of a cable channel and the economy of the apparatus.

Abstract: A gas insulated switchgear device of a double bus type which is accommodated in a metal container filled with SF.sub.6 gas includes first and second gas insulated main buses disposed horizontally and substantially in parallel with each other. Bus sectioning units section each of the first and second main buses into first and second sections. The bus sectioning units include auxiliary buses disposed outside of said first and second main buses. A branching bus connects one end of the first main bus with one end of one of the auxiliary buses via a circuit breaker. Another branching bus connects the other end of the first main bus with the other end of the one of the auxiliary buses. Still another branching bus connects one end of the second main bus with one end of another auxiliary bus. A further branching bus connects the other end of the second main bus with the other end of the other auxiliary bus. Potential transformers are provided along the branching buses.

Abstract: A power transmission system includes a transmission line unit for three phases connected to three gas insulated transmission lines and a standby transmission line unit for a phase connected to a standby gas insulated transmission line connected with each other. A connection bus is provided at a branch part of each breaker in the transmission line unit for three phases, via the breaker. The connection bus is connected to a branch bus provided between the breaker in the transmission line unit of a gas insulated switch gear for three phases and the main buses, and to the standby transmission line unit.