Hitachi, Ltd.

Kazuya Ooishi

Jun Ozawa

Katsuji Shindo

Yoshitaka Yagihashi

Takao Umeda

Yasuro Hori

Tatsuo Igawa

Shingo Shirakawa

Yoshiharu Nagae

Masato Isogai

Takeo Yamazaki

Satoshi Watahiki

Takahide Matsuo

Syuichi Terakado

A substation includes standard arresters installed near a bushing of a power transmission line entrance and at a connecting bus of a transformer and one or more high voltage arresters having a discharge voltage 10 to 30% higher than a standard arrester. Each high voltage arrester uses zinc oxide elements and is disposed on a line side of a line entrance breaker and/or near an open end of a double main bus in the substation.

Substation with surge arresters

In order to provide an arrestor for a gas insulated switchgear in which the voltage share rates of respective zinc oxide non-linear resistance elements are made uniform, in an arrestor constituted by a plurality of columns for a gas insulated switchgear, the thickness or the capacitance of insulator spacers contacting the high voltage terminal or the ground terminal in respective columns is controlled, whereby the potentials of the zinc oxide non-linear resistance elements close to the high voltage terminal or to the ground terminal in the respective columns are shifted close to the potentials of the high voltage terminal or the ground terminal.

Arrestor for gas insulated switchgear

An arrester for a gas insulated switchgear device includes a closed container filled with an insulating gas; a columnar piled body formed by piling up a plurality of zinc oxide resistance elements between a high voltage side terminal and a grounding side terminal disposed in the closed container; a plurality of potential equalizing rings electrically and mechanically connected to the high voltage side terminal of the columnar piled body, the potential equalizing rings being disposed in a discrete manner along the piling up direction of the zinc oxide resistance elements with a predetermined spacing distance while surrounding the outer circumference of the columnar piled body; and an intermediate electrode disposed around the columnar piled body at a position facing the potential equalizing ring located nearest to the grounding side terminal among the potential equalizing rings.

Arrester for gas insulated switchgear device

A zinc oxide type arrester including: four constitutional units electrically connected in parallel and a closed container accommodating the constitutional units. Each of the constitutional units includes a first columnar stack body composed by stacking zinc oxide elements and insulating spacers in a first predetermined order, a second columnar stack body composed by stacking zinc oxide elements and insulating spacers in a second predetermined order and a third columnar stack body composed by stacking zinc oxide elements and insulating spacers in a third predetermined order, the zinc oxide elements in the first, second and third columnar stack bodies contained in one constitutional unit are connected in series as a whole, and at least two of the three columnar stack bodies having same stacking structures in adjoining constitutional units are arranged to closely face each other.

Zinc oxide type arrester

Disclosed is a lightning arrester provided for a power transmission line so as to prevent damage to a line-supporting insulator string due to lightning stroke. A lightning arrester unit is fixedly supported on a fitting fixed to an arm structure of a tower in a relation in which its grounded side is electrically insulated from the fitting, and an operation detection device is connected between the grounded side of the lightning arrester unit and the fitting. The operation detection device is in the form of an operation indicator, a flashover indicator and/or an operation recorder. In the event of impartation of a lightning stroke, the operation detection device detects lightning current flowing from the grounded side of the lightning arrester unit toward the fitting.

Lightning arrester on tower for power transmission

In a driving method of an optical switch element for controlling a quantity of transmission light between opposed electrodes by interposing a transparent, high dielectric material between the opposed electrodes and applying a positive or negative voltage between the opposed electrodes, the improvement wherein a period in which the opposed electrodes are substantially short-circuited is disposed in order to make it possible to either reduce or eliminate stored charge.

Driving ferroelectric liquid crystal printers via short circuiting

A driving method for an optical printer and an optical printer having a liquid-crystal light switching element including a ferroelectric liquid crystal sandwiched between a pair of plates provided with electrodes on adjacent surfaces thereof. The liquid-crystal light switching element is disposed between a light source and a movable photosensitive surface and controlled so as to at least one of transmit and block light from the light source to the photosensitive surface for enabling a printing operation. Voltages v.sub.1 and v.sub.2 are applied to the liquid-crystal switching element substantially in accordance with the equation ##EQU1## and the intensity of light from the light source incident on the liquid-crystal switching element is controlled so that incident light intensity during a period T.sub.2 is weaker than the incident light intensity during a period T.sub.1, where t.sub.0, t.sub.1, t.sub.2 and t.sub.3 represents times, T.sub.1 (=t.sub.1 -t.sub.0) is the period during which a printing operation is effected, T.sub.2 (=t.sub.3 -t.sub.2) is the period during which the photosensitive surface moves, v.sub.1 is the voltage which is applied to the liquid-crystal switching element during the period T.sub.1, and v.sub.2 is the voltage which is applied to the liquid-crystal switching element during the period T.sub.2.

Growing community of inventors

Ibaraki, Japan

Kazuya Ooishi