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.

Abstract: The gas insulated switchgear includes a gas insulated double main bus, bus sectioning and bus tieing gas insulated switchgear units, a main bus potential transformer and a main bus work use earthing switch for respective main buses. The bus sectioning and bus tieing gas insulated switchgear units are respectively constituted by a vertical type circuit breaker, and the main bus potential transformer and the main bus work earthing switch provided for one of two main buses. When the vertically disposed circuit breaker is used for the bus sectioning and the bus tieing gas insulated switchgear units, the entire device is decreased in size in the horizontal direction.

Abstract: A grounding switch which includes a resistance contact unit and a short circuiting contact unit accommodated in a single sheath or casing. A movable contact of the short circuiting contact unit is connected to a movable contact of the resistance contact unit and a fixed contact of the short circuiting contact unit is grounded. A resistor is connected between the movable contact of the resistance contact unit and fixed contact of the short circuiting contact and is temporarily inserted into a main power circuit when the resistance contact unit is closed. The resistance contact unit and resistor are arranged on parallel axes in the same sheath.

Abstract: A three-phase combined type gas insulated bus is disclosed which comprises at least one eddy current conductor for passing the eddy current caused secondarily by the current flowing in high voltage conductors, thus solving the problem of a newly-found phenomenon that the temperature of a sealed casing increases by the flow of the eddy current. This eddy current conductor is made of such a material of good electrical conductivity as aluminum or copper. Even in the case where the sealed casing is reduced in diameter to such an extent as to pose a problem of temperature increase by the eddy current flow, the eddy current is reduced or completely eliminated in the best case, so that the sealed casing can be made of a low cost soft steel.