Hitachi, Ltd.

Hirohiko Yatsuzuka

Takanobu Aoyama

Masaki Hachida

Tokio Yamagiwa

Toshiaki Rokunohe

Manabu Takamoto

Tuneo Kishi

Isao Nishida

Masahiro Shimokawa

Kenji Annou

Tadasuke Yamamoto

Takashi Minakawa

Yoshikatsu Enokida

The present invention provides a method and device for detecting a discharge in an electrical device comprising, providing a bushing having a bottom lower flange and a top upper flange, providing a shield inside the bushing extending from the bottom lower flange to a position at least below the top upper flange and providing an antenna outside the bushing at least above the position for measuring an output signal from the device for detecting the discharge.

Method and device for detecting a partial discharge in an electrical device

A gas-insulated electrical apparatus includes tanks into each of which insulation gas is sealed, including bus-bars, bus-bar disconnectors connected to the bus-bars, circuit breakers connected to the bus-bar disconnectors, and line disconnectors connected to the circuit breakers, each line disconnector being further connected to a transmission or a transformer; wherein each bus-bar disconnector and each line disconnector include a respective pair of a fixed-contact and a moving-contact, the fixed-contact and the moving-contact being concave and convex, respectively, and each of the moving-contacts in the bus-bar disconnector and the line disconnector is located at the side of a corresponding circuit breaker between the bus-bar disconnector and the line disconnector, a contact-parting speed in the line connector being lower than that in the bus-bar disconnector.

Gas-insulated electrical apparatus

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.

Gas insulated switchgear apparatus

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.

Gas insulated switchgear

A three-phase common tank type gas circuit breaker has a grounded tank filled with an insulating gas and accommodating three interrupter assemblies for three phases of the electric power. Each assembly includes a parallel electrical connection of an interrupter having stationary and movable contacts, a capacitor and a closing resistor. The interrupters for the three phases are disposed in spaced relationship circumferentially of the tank and have axes extending axially of the tank. The closing resistor for each phase is disposed on one side of the associated interrupter adjacent an adjacent interrupter for a different phase, while the capacitor for each phase is disposed on the inner or outer side of the associated interrupter, whereby the radial and axial dimensions of the grounded tank can be reduced.

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Hitachi, Japan

Hirohiko Yatsuzuka