Hitachi, Ltd.

The Tokyo Electric Power Company, Incorporated

Yoshiyasu Watanabe

Toru Tanimizu

Takashi Funawatari

Ayumu Morita

Satoru Kajiwara

Yozo Shibata

Toshio Horikoshi

Ryutaro Yamamoto

Nobuhiro Kuroda

Kazuo Kano

Yasunobu Kanou

Koji Kondou

Compatibility with a current transformer having several kinds of rated current ratios is achieved by finding out a formula of relationship between errors arising in a transformer input circuit and detectable ranges set as setting values of the input circuits which can be optimally set. In connection with that, by dispensing with a gain control section, the number of components, the mounting area and the cost can be reduced. Arithmetic expressions representing the relationship among errors arising in the transformer input circuit, the instrumentation ranges of the input circuits, and detectable errors have been derived. Further by optimally setting the detectable ranges of the input circuits, which are the parameters of the arithmetic expressions, the configuration compatible with a current transformer having several kinds of rated current ratios is achieved.

Protective relay apparatus

A vacuum switch gear provided with a vacuum container grounded within a grounded vacuum container or a gas-insulated ground container, and a pair of buses connected to an external conductor of the switch gear. A portion for connecting the buses and the external conductor is interface insulation in which an elastic body and solid insulation are utilized in combination. The interface insulation performs adhering and tightening work by rotating an adjuster from the outside.

Vacuum switchgear

A protection apparatus for a spot network substation has a plurality of receiving lines connected between a network bus and a plurality of power sources. Each receiving line is connected to a primary switching device, a network transformer and a protector CB. A detector for detecting a phase of each receiving line voltage and a judging unit for judging the detected phase are provided on the primary side of each network transformer. A previously stored basic phase is compared with the detected phase of the receiving line voltage. If there is a lag in the detected phase of the receiving line voltage, it is judged to be a power-stop of the corresponding power source and the protector CB is tripped.

Protection system for power receiving station

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Hitachi, Japan

Yoshiyasu Watanabe