VACUUM SWITCH AND VACUUM SWITCH GEAR

Abstract: The present invention provides a vacuum switch and a vacuum switchgear which can be made substantially small in size and substantially light in weight and can improve safety during maintenance and inspection work. In order to attain the above object, the vacuum switch comprises a vacuum container composed of solid insulators and a metallic container covered with an insulation; and a fixed electrode and a movable electrode which are insulated from each other. The vacuum switchgear is constructed using the vacuum switches.

Description: FIELD OF THE INVENTION The present invention relates to a vacuum switch and a vacuum switchgear characterized by a grounded vacuum container which is composed of a metallic container coated with an insulation having a grounding layer on its outer surface and a solid insulator. BACKGROUND OF THE INVENTION Referring to FIG. 4, an arc shield 9 for suppressing a stain along a surface of an insulator 2 is arranged inside a vacuum container of a vacuum switch 1. However, there is a limitation in reducing the radial dimension of the vacuum switch because it is necessary to pay an attention on the electric field in the end portions of the arc shield 9. In a conventional vacuum switch 1, the metallic container 3a and a bus side conductor 14 are charged portions and are exposed to atmosphere. Another type of vacuum switch is described in the patent laid open publication EP 01 176 665, which is considered to represent the closest prior art. This vacuum switch comprises a vacuum switch chamber and a insulation housing which includes the chamber. The metallic container of the chamber, which includes the electrodes, is not exposed to atmosphere but to an insulating gas in the housing. For providing the gas a cavity is formed between the vacuum switch chamber and the insulation housing. In a case where the vacuum switches 1 are used for a vacuum switchgear, it is necessary to take it into consideration to keep sufficient insulation distances between the charged portion and phases, actuators and an enclosing cabinet, as shown in FIG. 5 and FIG. 6. Therefore, there is a limitation in that the switchgear is made small in size drastically. Further, since the metallic container 3a and the bus side conductor 14 are the charged portions, an inter-phase short-circuit or a grounding fault occurs caused by erroneous contact, and sometime the accident may result in injury. It is required to develop a compact distribution and transformation system which can improve safety to reduce occurrence of electric shock accidents during maintenance and inspection work and can solve a problem of difficulty of acquiring of a distribution and transformation substation site in order to cope with the increasing demand of consumed electric power in a congested urban district. An object of the present invention is to provide a vacuum switch and a vacuum switchgear which can improve safety during maintenance and inspection work and can be made substantially small in size and substantially light in weight. SUMMARY OF THE INVENTION The above object is solved by a vacuum switch according to claim 1 and a vacuum switch gear according to claims 4 and 5. The dependent claims are directed to preferred embodiments of the invention. An embodiment of the present invention provides a vacuum switchgear comprising vacuum switches and a control portion for controlling operating mechanisms, wherein each of the vacuum switches comprises a grounded vacuum container in which a metallic container and insulators are gas-tightly fixed with, for example, a ceramic, said metallic container being coated with an insulation, a grounding layer being provided on its outer surface; a fixed electrode arranged through the solid insulator; a movable electrode arranged through the solid insulator and in a positional relationship of touching to and detaching from the fixed electrode; and a moving portion connected to the operating mechanism for driving the movable electrode and to the movable electrode. In the present invention, the switch means a machine which performs making and breaking between the fixed electrode and the movable electrode. The switchgear means a machine which includes a control gear and contains a combination of one or more switching units, one or more units among a operating, a measurement, a protecting and an adjusting units, and inner connections in an enclosed box. Further, in addition to the structures described above, the switchgear further comprises a group of these machines and units having accessories and supporting structures, and furthermore comprises a control portion for controlling the operating mechanism. In an embodiment of the present invention, a vacuum pressure is below 133·10 -4 Pa (10 -4 Torr), preferably below 133·10 -6 Pa (10 -6 Torr), and particularly it is preferable that the pressure is below 133·10 -8 Pa (10 -8 Torr). Therefore, in order to keep the withstanding voltage between the bus side conductor and the grounding layer and between the load side conductor and the grounding layer, the surface shape of the solid insulators in the atmosphere side is necessary to lengthen the distance along the surface exposing to the atmosphere as long as possible. For example, it can be considered that the shape is a smooth curvilinear surface, or a partially or fully folded surface. The materials for the insulator considered are insulating materials such as epoxy resin, ceramic and so on, but an insulating rubber having a high adhering property with the metallic container is preferable. The grounding layer provided on the outer surface of the insulator may be formed by applying, plating or adhering an electric conductive material to the surface. A vacuum switch in accordance with an embodiment of the present invention comprises: a solid insulator for insulating between a metallic container and a fixed electrode; a solid insulator for insulating between the metallic container and a movable electrode; a grounded vacuum container composed of the metallic container covered with an insulation having a grounding layer on an outer surface and the solid insulators; and the movable electrode gas-tightly sealed inside the vacuum container, the movable electrode being driven by an operating mechanism. Further, in an embodiment, the fixed electrode is gas-tightly sealed inside the vacuum container, the fixed electrode being connected to an electric power line. Furthermore, a vacuum switchgear in accordance with the present invention comprises: vacuum switches; operating mechanisms for driving a movable electrode; an operation compartment for controlling operating mechanisms; and a grounded vacuum container containing the vacuum switches, the operating mechanisms and the operation compartment, wherein each of the vacuum switches is structured as set forth above. BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a cross-sectional view showing an embodiment of a vacuum switch in accordance with the present invention. FIG. 2 is a cross-sectional view showing an embodiment of a vacuum switchgear in accordance with the present invention. FIG. 3 is a cross-sectional side view showing an embodiment of a vacuum switchgear in accordance with the present invention. FIG. 4 is a cross-sectional view showing a conventional vacuum switch. FIG. 5 is a cross-sectional view showing a conventional vacuum switchgear. FIG. 6 is a cross-sectional side view showing a conventional vacuum switchgear. DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the basic structure of an embodiment of a vacuum switch 1 in accordance with the present invention. A vacuum container is composed of a metallic container 3, solid insulators 2a and 2b, an insulator 4 and a grounding layer 5. The metallic container 3 of the vacuum container is made of, for example, stainless steel. The solid insulators 2a and 2b are fixed to the upper portion and the lower portion of the metallic container 3, and a fixed electrode 6 and a movable electrode 7 are attached to the solid insulators 2a and 2b, respectively. In detail, the solid insulators 2a and 2b are made of alumina ceramic. The movable electrode 7 is supported by the solid insulator 2b through a bellows. The movable electrode 7 can be vertically moved by an operating rod. The fixed electrode 6 and the movable electrode 7 are gas-tightly sealed inside the vacuum container. Vacuum is one of the best insulation, and accordingly by sealing the electrodes in the grounded vacuum container, the insulation distance to the other components can be decreased. A highly adhesive insulation rubber is used for the insulator 4 coating the metallic container 3. The grounding layer 5 provided on the outer surface of the insulator 4 may be formed by applying, plating or adhering an electric conductive material to the surface. Since the metallic container 3 serves as an arc shield, there is no need to form the metallic container in a complex shape as in the conventional one and consequently the metallic container can be formed compact in the radial direction. FIG. 2 and FIG. 3 show the basic structure of an embodiment of a vacuum switchgear in accordance with the present invention. Because each of the vacuum switches is grounded, the vacuum switch for one phase can be arranged near the vacuum switch for the other phase and the actuator. Accordingly, the distance between the vacuum switches, the distance between the vacuum switch and the actuator and the enclosing cabinet can be narrowed, and the vacuum switchgear can be made small in size and light in weight. According to the present invention, the distance between the vacuum switches, the distance between the vacuum switch and the actuator and the enclosing cabinet can be narrowed. Thereby, it is possible to provide a vacuum switchgear which is substantially small in size and substantially light in weight. Further, since the switches are grounded, safety during maintenance and inspection work can be improved.

Claims: A vacuum switch comprising a vacuum container having : a metallic container (3); a solid insulator (2a) for insulating between said metallic container (3) and a fixed electrode (6), which is gas-tightly enclosed inside said vacuum container, and is connected to an electric power line; and a solid insulator (2b) for insulating between the metallic container(3) and a movable electrode (7), which is gas-tightly enclosed inside said vacuum container and to be brought into contact with or to be separated from the fixed electrode (6) by an operating mechanism, characterized in that said vacuum container is grounded, and the metallic container (3) is coated with an insulation (4), which has a grounding layer (5) formed on its outer surface. The vacuum switch of claim 1, wherein the grounding layer is formed by plating the outer surface of the insulation with a conductive material, or by applying or adhering the conductive material on the outer surface of the insulation. The vacuum switch according to claim 1 or 2, wherein an atmospheric side of the solid insulators has a smooth curvilinear surface, or a partially or fully folded surface. A vacuum switchgear comprising a plurality of vacuum switches according to any one of claims 1 to 3, whose phases are adjacent to each other. A vacuum switchgear comprising a plurality of vacuum switches according to any one of claims 1 to 3, each phase of which is adjacent to an actuator.

Inventors: KOJIMA KATSUNORI, MIYO TAKUYA, TANIMIZU TORU, KOJIMA, KATSUNORI, MIYO, TAKUYA, TANIMIZU, TORU, KOJIMA, Katsunori, Kokubu Works, Hitachi, Ltd., MIYO, Takuya, Kokubu Works, Hitachi, Ltd., TANIMIZU, Toru, Kokubu Works, Hitachi, Ltd.
Applicants: HITACHI LTD, HITACHI, LTD.
Application year: 1999
Main classification: H01H33
IPC codes: H01H33