Switchgear having main circuit switches disposed in separate vacuum chambers

The present application claims priority from Japanese application serial No. 2007-033006, filed on Feb. 14, 2007, the content of which is hereby incorporated by reference into this application.

1. Field of the Invention

The present invention relates to a vacuum switchgear, and more particularly, to a multi circuit type vacuum switchgear having plural main circuit switches in a non-earthed vacuum chamber or chambers.

2. Description of Related Art

A multi circuit type vacuum switchgear is used in, e.g., an electric distribution system for electrical distribution to the demanding side. This type of vacuum switch gear has plural main circuit switches in a non-earthed vacuum chamber or chambers.

Patent Document 1 discloses a vacuum switchgear comprising a mold portion in which a conductor connected with a fixed electrode side of a vacuum switch is molded with resin, and a vacuum chamber which encases the switch having the fixed electrode and a movable electrode that can connect with and separate from the fixed electrode.

Patent Document 2 discloses a switchgear comprising a vacuum chamber, which encases a switch or plural switches for connecting with and separating from fixed electrodes and movable electrodes which connect with different outer conductors and which is molded and protruded out of an insulator. Plural terminals for connecting the fixed electrodes and the movable electrodes with the outer conductors project from the mold portion.

Patent Document 3 discloses a vacuum isolated switchgear comprising a vacuum chamber and a necessary number of switches encased in the vacuum chamber, in which the vacuum chamber is formed of metal materials and is covered with mold of insulating materials.

Patent Document 4 discloses a switchgear whose main circuit switches each having fixed side electrode and movable side electrode are encased in a vacuum chamber and the corresponding main circuit conductors thereof are installed through a wall of the vacuum chamber.

Patent Document 1: Japanese Patent Laid-open No. 2006-238522 Patent Document 2: Japanese Patent Laid-open No. 2000-306474 Patent Document 3: Japanese Patent Laid-open No. 2001-126595 Patent Document 4: Japanese Patent Laid-open No. 2001-135207

The above-described multi circuit type vacuum switchgear has a function for connection change in accordance with change of power load capacity on the power demanding side. If the withstand voltage performance of the vacuum switchgear becomes low, the devices on the downstream side are much influenced.

Accordingly, improvement in the reliability of the vacuum switchgear is required, and further, downsizing and price reduction of the vacuum switchgear are required. Particularly, in recent years, the reliability of ground isolation is strongly required.

The present invention was made in view of the above-described situation, and provides a multi circuit type vacuum switchgear with improved reliability of the ground isolation.

The present invention provides a vacuum switchgear comprising; a plurality of main circuit switches, wherein each of movable electrodes of the main circuit switches is connected to an air insulated rod, which is connectable to an operating rod, and wherein each of fixed electrodes of the main circuit switches is connected to a bushing conductor extending from the vacuum chamber, a plurality of earthing switches a fixed electrode of which is electrically connected to a fixed electrode of the main circuit switches, a non-earthed vacuum chamber accommodating the main circuit switches, an earthed insulating mold casing that encloses the vacuum chamber, air insulated rod and bushing conductor, and a lid that air-tightly closes the top portion of the mold casing.

FIG. 1 is a front view showing an example of the entire structure of a switching apparatus employing the vacuum switchgear according to the present invention.

FIG. 2 is a top view showing the example of the entire structure of the switching apparatus employing the vacuum switchgear according to the present invention shown in FIG. 1 .

FIG. 3 is a connecting diagram showing an example of the switching apparatus employing the vacuum switchgear according to the present invention.

FIG. 4 is a longitudinal front, cross-sectional view showing an embodiment of the vacuum switchgear according to the present invention.

FIG. 5 is a longitudinal side, cross-sectional view showing the embodiment of the vacuum switchgear according to the present invention in FIG. 4 .

FIG. 6 is a longitudinal front, cross-sectional view showing another embodiment of the vacuum switchgear according to the present invention.

FIG. 7 is a longitudinal front, cross-sectional view showing another embodiment of the vacuum switchgear according to the present invention.

FIG. 8 is a longitudinal front, cross-sectional view showing still another embodiment of the vacuum switchgear according to the present invention.

FIG. 9 is a top view of the vacuum switchgear according to the present invention shown in FIG. 8 .

FIG. 10 is a longitudinal side, cross-sectional view showing the embodiment of the vacuum switchgear according to the present invention shown in FIG. 8 .

FIG. 11 is a longitudinal back, partially cross-sectional view showing the embodiment of the vacuum switchgear according to the present invention shown in FIG. 8 .

FIG. 12 is a longitudinal back, partially cross-sectional view showing another embodiment of the vacuum switchgear according to the present invention shown in FIG. 9 .

FIG. 13 is a longitudinal back, partially cross-sectional view showing another embodiment of the vacuum switchgear according to the present invention shown in FIG. 10 .

There are exemplified several aspects of the present invention, such as:

The vacuum switchgear, wherein the vacuum switchgear comprises the plurality of main circuit switches accommodated in a single non-earthed vacuum chamber accommodating the main circuit switches, the adjoining movable electrodes of the adjoining main circuit switches being electrically connected in the non-earthed vacuum switches.

The vacuum switchgear, wherein the vacuum switchgear comprises the plurality of main circuit switches each being accommodated in a single non-earthed vacuum chamber, the adjoining movable electrodes of the main circuit switches being electrically connected to each other outside the non-earthed vacuum chamber.

A vacuum switchgear comprising; a single non-earthed vacuum chamber accommodating a plurality of main circuit switches each of the switches comprising movable electrode and fixed electrode, the adjoining movable electrodes being electrically connected to each other in the vacuum chamber, a plurality of bushing conductors electrically connected to the corresponding fixed electrodes of the main circuit switches and extended from the non-earthed vacuum chamber, earthing switches each being accommodated in a vacuum chamber separated from the non-earthed vacuum chamber or in an air chamber at positions corresponding to the main circuit switches, air-insulated rods connected to the corresponding movable electrodes of the main circuit switches for transferring movement of an operating mechanism, an earthed resin mold casing that air-tightly surrounds the non-earthed vacuum chamber, the bushing conductors and the vacuum chambers or air chambers of the earthing switches, and a lid air-tightly closing the top of the mold casing.

A vacuum switchgear according to one aspect of the present invention comprises a plurality of main circuit switches disposed in a single non-earthed vacuum chamber, each of the main circuit switches comprising fixed electrode and movable electrode in a non-earthed vacuum chamber. The respective movable electrodes of adjoining main circuit switches are electrically connected with flexible conductors. Operation rods on the movable electrode side are connected to insulating rods in the non-earthed vacuum chamber. The movable side operation rods are interconnected with the respective movable electrodes through insulators or insulating rods. A mold casing around the vacuum chamber, air insulating rods and bushing conductors comprises a first insulating mold part for insulating the bushing conductors connecting to the main circuit switches, a second insulating mold part integrated with the first mold part for insulating the movable electrodes side and the operation rods on the movable electrode side.

Further, a vacuum switchgear according to another aspect of the present invention comprises a plurality of main circuit switches in a single vacuum chamber, accommodating the main circuit switches each comprising a fixed electrode and a movable electrode in the vacuum chamber. The movable electrodes are electrically connected each other with flexible conductors. The operation rods on the movable electrode side are connected with the respective movable electrodes. A mold casing including a first insulating mold part for insulating a plurality of bushing conductors. The main circuit switches and the fixed electrodes, and a second insulating mold part is integrated with the first mold part for insulating the flexible conductors and the operation rods.

According to the present invention, a vacuum switchgear becomes inexpensive and downsized, and further, the performance of ground isolation in the multi circuit type vacuum switchgear is improved; thus the reliability can be further improved.

FIGS. 1 and 2 show an example of the entire structure of a switching apparatus that employs the vacuum switchgear according to the present invention to which a transformer 74 is connected. FIG. 1 is a front view and FIG. 2 , a top view of FIG. 1 . In FIG. 1 , reference numeral 70 denotes a vacuum switchgear according to the present invention; 71 , an operating mechanism section; 72 , a cable chamber; 73 , a fuse chamber; 74 , a transformer chamber; and 75 , a low voltage chamber. In FIG. 2 , reference numerals 70 U to 70 W denote respective vacuum switch modules connected with a three-phase power supply.

FIG. 3 is a connecting diagram showing an example of the vacuum switchgear according to the present invention. In this example, an example of a 3-circuit switching is shown. In FIG. 3 , numerals 103 a to 103 c denote main circuit switches; 104 a to 104 c , earthing device; 105 a to 105 c , bushings; and 106 a to 106 c , cables.

FIGS. 4 and 5 show an embodiment of the vacuum switchgear according to the present invention. FIG. 4 is a longitudinal front view; and FIG. 5 , a longitudinal side view of FIG. 4 . In these figures, this embodiment has three main circuit switches (current interrupters) with fixed electrodes 9 A to 9 C and movable electrodes 5 A to 5 C respectively open/close to the fixed electrodes 9 A to 9 C. These main circuit switches are accommodated in a non-earthed type vacuum chamber 1 . An inside of the non-earthed type vacuum chamber 1 is kept a low-pressure condition.

The contacts of the fixed electrodes 9 A to 9 C and of the movable electrodes 5 A to 5 C are formed from a material dispersing a powder of chromium (Cr) i.e. a fireproof metal in a matrix of an alloy of copper (Cu) i.e. a high conductive metal, and a member selected from tellurium (Te), bismuth (Bi) or tin (Sn) of a low melting point metal. Another parts of the fixed electrodes 9 A to 9 C and the movable electrodes 5 A to 5 C are electrode rods and formed from oxygen free copper (pure copper). The contacts are connected to the oxygen free copper with brazing.

Arc shields 7 A to 7 C are respectively provided in portions corresponding to the respective main circuit switches. Upper ceramics cylinders 6 A to 6 C and lower ceramics cylinders 8 A to 8 C are provided on the peripheries of these arc shields 7 A to 7 C. The upper ceramics cylinders 6 A to 6 C have holes to allow insertion of the movable electrodes 5 A to 5 C in their upper parts. The lower ceramics cylinders 8 A to 8 C have end plates (lids) to allow insertion of the fixed electrodes 9 A to 9 C in their lower parts. Fixed side seal rings 10 A to 10 C are respectively provided in the insertion portions of the lower ceramics cylinders 8 A to 8 C for insertion of the fixed electrodes 9 A to 9 C.

Bushing conductors 12 A to 12 C are integrally coupled to the fixed electrodes 9 A to 9 C. The movable electrodes 5 A to 5 C are electrically interconnected with flexible conductors 20 and 21 covered with bellows on the surface side. One ends of movable operating rods 3 A to 3 C are respectively coupled via insulators 4 A to 4 C to the respective movable electrodes 5 A to 5 C. The movable operating rods 3 A to 3 C are guided out of the vacuum chamber 1 through guides 13 A to 13 C provided on an upper surface of the vacuum chamber 1 . The ends of the movable operating rods 3 A to 3 C opposite to the sides connected to the insulators 4 A to 4 C are respectively coupled to insulated operating rods in the air 14 A to 14 C. In the vacuum chamber 1 in which the guides 13 A to 13 C are provided, bellows 2 A to 2 C, with one ends connected to the vacuum chamber 1 and the other ends connected to the movable operating rods 3 A to 3 C, are respectively provided such that the movable operating rods 3 A to 3 C can move vertically. The bellows 2 A to 2 C hold airtight sealing in the vacuum chamber 1 .

The insulated operating rods in the air 14 A to 14 C are called air-insulated rods. The air-insulated rods are connected for transferring a movement of the operating mechanism to the corresponding movable electrodes of the main circuit switches.

Earthing switches are connected to the fixed electrodes 9 A to 9 C of the respective main circuit switches. An example where the earthing switch is connected to the fixed electrode 9 C of the switch will be described using FIG. 5 .

In FIG. 5 , as the elements having the same reference numerals as those in FIG. 4 are the same elements, the detailed explanations of the elements will be omitted. The earthing switch has an earthing switch fixed electrode 37 C and an earthing switch movable electrode 31 C. An air insulated operating rod 30 C for earthing switch is coupled to the earthing switch movable electrode 31 C. The earthing switch fixed electrode 37 C is connected via a conductor 38 C to the fixed electrode 9 C of the switch. An earthing switch arc shield 34 C is provided between opposed portions of the earthing switch fixed electrode 37 C and the earthing switch movable electrode 31 C.

An earthing switch upper ceramics cylinder 33 C and an earthing switch lower ceramics cylinder 35 C are respectively provided on the periphery of the earthing switch arc shield 34 C. The earthing switch upper ceramic cylinder 33 C has a hole to allow insertion of the earthing switch movable electrode 31 C in its upper part. An earthing switch bellows 32 C is provided between the end plate of the earthing switch upper ceramic cylinder 33 C and the earthing switch movable electrode 31 C.

The earthing switch lower ceramic cylinder 35 C has an seal ring 36 C to allow insertion of the earthing switch fixed electrode 37 C in its lower part. An earthing switch fixed side seal ring 36 C is provided in the insertion portion of the earthing switch lower ceramic cylinder 35 C for insertion of the earthing switch fixed electrode 37 C.

In the present embodiment, a molded part 22 is formed on the periphery of the non-earthed type vacuum chamber 1 . As shown in FIG. 4 , the molded part 22 has a first insulating member 22 a to insulate the side of the fixed electrodes 9 A to 9 C of the switch and the bushing conductors 12 A to 12 C on the fixed electrode side, and a second insulating member 22 b , integrally formed with the first insulating member 22 a , to insulate the side of the movable electrodes 5 A to 5 C and the side of the movable operating rods 3 A to 3 C.

The non-earthed type vacuum chamber 1 , the bushing conductors 12 A to 12 C and a vacuum chamber for earthing switches are molded integratedly and airtightly, and the molded part 22 is formed. A molded cover 23 , that is to say, a lid is installed airtightly on an end of the second insulating member 22 b which is a part of this molded part 22 . Dry air is enclosed in a space distinguished by the molded part 22 and the molded cover 23 . A conductive paste or a conductive paint etc. is coated on the outside of the epoxy resin mold casing including the molded part 22 to earth the casing. That is to say, the outside of the molded part 22 can be earthed through the conductive coating. This molded part 22 is called an earthed mold casing.

The reason why the non-earthed type vacuum chamber 1 and the vacuum chamber for earthing switches are different vacuum chambers is because the latter vacuum chamber is not influenced when a vacuum degree in the former vacuum chamber deteriorated.

More particularly, the first insulating member 22 a is an epoxy resin mold covering the periphery of the vacuum chamber 1 corresponding to the fixed electrodes 9 A to 9 C and the peripheral surfaces of the busing conductors 12 A to 12 C on the fixed electrode side. The second insulating member 22 b is an epoxy resin mold, integrally formed with the epoxy rein mold as the first insulating member 22 a , covering the periphery of the vacuum chamber 1 corresponding to the side of the movable electrodes 5 A to 5 C and the side of the movable operating rods 3 A to 3 C. Further, as shown in FIG. 5 , the earthing switch is provided in another section of that of the non-earthed type vacuum chamber, and integrally molded with the non-earthed type vacuum chamber 1 with the first insulating member 22 a . Further, the bushing conductors 12 A to 12 C are integrally covered with the epoxy resin mold as the first insulating member 22 a , thereby forming insulated bushings 11 A to 11 C.

As described above, in the present embodiment, the three main circuit switches, the flexible conductors 20 and 21 , and a part of the movable electrode side of the movable operating rods 3 A to 3 C are accommodated in one non-earthed type vacuum chamber 1 , and insulated with the first insulating member 22 a covering the peripheral surface of the non-earthed type vacuum chamber 1 and the peripheral surfaces of the bushing conductors 12 A to 12 C on the fixed electrode side, and the second insulating member 22 b . The movable operating rods 3 A to 3 C are guided out of the vacuum chamber 1 via the bellows 2 A to 2 C, and air-insulated.

In FIG. 5 , electric contacts of the movable electrode 5 C and the fixed electrode 9 C, that is, a movable contact and a fixed contact of the main circuit switch are encased in a switching zone formed in an area of the molded part 22 . The movable contact and the fixed contact are parts of near the electric contacts of the movable electrode 5 C and the fixed electrode 9 C, and are formed from a copper ally brazed on ends of electrode rods formed from oxygen free copper. The construction of this copper ally is described hereinbefore.

The switching zone is formed in a concave of the first insulating member 22 a formed in a deepest area of a part inside the molded part 22 in which non-earthed type vacuum chamber 1 is installed. This switching zone includes an upper ceramic cylinder 6 C, a lower ceramic cylinder 8 C and a fixed side seal ring 10 C. Further, an arc shield 7 C is encased in the switching zone. In this embodiment, the switching zone is installed in the concave of the first insulating member 22 a , and the lower ceramic cylinder 8 C and the fixed side seal ring 10 C are covered by the molded part 22 . But the switching zone is not necessarily installed in the concave of the first insulating member 22 a and the lower ceramic cylinder 8 C and the fixed side seal ring 10 C are not necessarily covered by the molded part 22 . That is, the lower ceramics cylinder 8 C may crop out in the non-earthed type vacuum chamber 1 , or the lower ceramic cylinder 8 C and the fixed side seal ring 10 C may crop out in the non-earthed type vacuum chamber 1 .

As shown in this figure, because a hole having a diameter a little bit larger than a diameter of the movable electrode 5 C is provided on a plane portion of the upper ceramic cylinder 6 C, dispersion of metal vapor into another area of the vacuum chamber 1 , generated by electric discharge etc. when the movable electrode 5 C and the fixed electrode 9 C contact or separate each other, can be suppressed.

Further, contacts of an earthing switch movable electrode 31 C and an earthing switch fixed electrode 37 C, that is, the movable contact and the fixed contact are encased in the switching zone covered with the molded part 22 . This switching zone includes an upper ceramic cylinder 33 C, a lower ceramic cylinder 35 C and a fixed side seal ring 36 C. Moreover, an arc shield 34 C is encased in the switching zone.

An area surrounded with a bellows 32 C, the upper ceramic cylinder 33 C, the lower ceramic cylinder 35 C and a fixed side seal ring 36 C, etc. are kept vacuum (a low pressure condition). This is called a vacuum chamber for the earthing switch. The earthing switch has electric contacts encased in the vacuum chamber for the earthing switch corresponding to the main circuit switch.

Further, although the molded cover 23 is not shown in FIG. 5 , the molded cover 23 may be installed as same as in FIG. 4 .

According to the above-described embodiment of the vacuum switchgear of the present invention, the three main circuit switches, the flexible conductors 20 and 21 and a part of the movable electrode side of the movable operating rods 3 A to 3 C are accommodated in one non-earthed type vacuum chamber 1 , and an insulating member of epoxy resin mold is formed on the peripheral surface of the non-earthed type vacuum chamber 1 including the peripheral surfaces of the bushing conductors 12 A to 12 C. Accordingly, a multicircuit type vacuum switch gear with further improved ground isolation reliability can be provided.

Further, in this embodiment, as the vacuum chamber 1 is anon-earthed chamber, the isolation performance is stabilized, and the structure is simplified. Further, as the arc shields 7 A to 7 C in the respective main circuit switches are previously installed in the vacuum chamber 1 , the assembly work is improved. In addition, as the respective main circuit switches can be individually operated in a practical operation, no branch current to the arc shields 7 A to 7 C occurs when electric current is cut off or is thrown into.

FIG. 6 is a longitudinal front view showing another embodiment of the vacuum switchgear according to the present invention. In FIG. 6 , as the elements having the same reference numerals as those in FIGS. 4 and 5 are the same elements, the detailed explanations of the elements will be omitted.

In this embodiment, in the main circuit switches, the upper ceramics cylinders 6 A to 6 C and the lower ceramics cylinders 8 A to 8 C have a tubular cylindrical shape.

In this figure, different from the cases of FIGS. 4 to 5 , the upper ceramic cylinders 6 C has no flat face, constituted only by a cylindrical sidepiece. Because the switching zone is encased in the concave of the first insulating member 22 a formed in the deepest area of the part inside the molded part 22 in which non-earthed type vacuum chamber 1 is installed, dispersion of metal vapor, generated by electric discharge etc. into another area of the vacuum chamber 1 can be suppressed.

Further, the same as in FIG. 4 , the molded cover 23 , that is, the lid is provided airtightly on the end of the second insulating member 22 b which is the part of the molded part 22 . Dry air is enclosed in a space formed of the molded part 22 and the molded cover 23 . Further, a conductive paste or a conductive paint etc. is coated on the epoxy resin mold including the molded part 22 is to unify electric potential of the casing with that of the outside.

According to the present embodiment, as in the case of the above-described embodiments, the occurrence of grounding due to particles generated in the vacuum chamber 1 can be suppressed, and a multi circuit type vacuum switchgear with further improved reliability can be provided. Further, in the main circuit switches, the upper ceramics cylinders 6 A to 6 C and the lower ceramics cylinders 8 A to 8 C have a tubular cylindrical shape without end plate. As the structure of the upper ceramics cylinders 6 A to 6 C and the lower ceramics cylinders 8 A to 8 C is simplified, the costs can be reduced.

FIG. 7 is a longitudinal front view showing another embodiment of the vacuum switchgear according to the present invention. In FIG. 7 , as the elements having the same reference numerals as those in FIGS. 4 to 6 are the same elements, the detailed explanations of the elements will be omitted.

In this embodiment, the bellows covering the flexible conductors 20 and 21 in the embodiment shown in FIG. 6 are removed and the flexible conductors 20 and 21 are used as simple bodies, thereby the structure of the conductors is simplified. Further, the bellows 2 A to 2 C for airtight sealing in the guides 13 A to 13 C in the vacuum chamber 1 shown in FIG. 6 are provided on the upper outside of the vacuum chamber 1 . Further, to reduce the vacuum volume in the vacuum chamber 1 , the lower parts of the bellows 2 A to 2 C are airtightly attached to the outside upper surface of the vacuum chamber 1 , and the upper part of the bellows are airtightly attached to the movable operating rods 3 a to 3 C guided out of the vacuum chamber 1 . In this case, the guides (not shown) are provided in touch with the insulated operating rods in the air 14 A to 14 C, thereby the vertical moving direction of the movable side can be regulated. Further, as shown in the switch on the right side in FIG. 7 , when the arc shield 7 A is integrated with the vacuum chamber 1 , the number of parts can be reduced.

According to the present embodiment, as in the case of the above-described embodiments, a multi circuit type vacuum switchgear with further improved ground isolation reliability can be provided. Further, as the vacuum volume in the vacuum chamber 1 and the number of parts can be reduced, the costs can be further reduced.

FIGS. 8 to 11 show another embodiment of the vacuum switchgear of the present invention. FIG. 8 is a longitudinal front view; FIG. 9 is a plan view of FIG. 8 ; FIG. 10 is a longitudinal side view of FIG. 8 ; and FIG. 11 is a longitudinal back view of FIG. 8 . In these FIGS. 8 to 11 , in this example, the vacuum switchgear has three main circuit switches (current interrupters) including the fixed electrodes 9 A to 9 C and the movable electrodes 5 A to 5 C open/close to the fixed electrodes 9 A to 9 C. The bushing conductors 12 A to 12 C are respectively integrally coupled to the fixed electrodes 9 A to 9 C.

The above-described respective main circuit switches are respectively accommodated in the vacuum chamber 1 . The respective vacuum chambers 1 have the upper ceramics cylinders 6 A to 6 C, the lower ceramics cylinders 8 A to 8 C, movable side seal rings 15 A to 15 C provided on the upper side of the upper ceramics cylinders 6 A to 6 C, having outlet portions for the movable electrodes 5 A to 5 C, the fixed side seal rings 10 A to 10 C provided on the lower side of the lower ceramics cylinders 8 A to 8 C, and the bellows 2 A to 2 C provided inside the movable side seal rings 15 A to 15 C, with one ends provided on the movable electrodes 5 A to 5 C inside the vacuum chamber 1 and the other ends connected airtightly with the movable side seal rings 15 A to 15 C. That is to say, each of the non-earthed type vacuum chambers accommodates a pair of fixed electrode and movable electrode of the main circuit switches.

The bellows 2 A to 2 C respectively connected to the movable electrodes 5 A to 5 C enable vertical motion of the movable electrodes 5 A to 5 C, and holds airtight sealing in the vacuum chamber 1 . In the respective vacuum chambers 1 , the arc shields 7 A to 7 C are provided in portions corresponding to the respective main circuit switches. The guides 13 A to 13 C to guide the movable electrodes 5 A to 5 C guided out of the vacuum chamber 1 are provided on the upper surfaces of the movable side seal rings 15 A to 15 C. The insulated operating rods in the air 14 A to 14 C are provided at the ends of the movable electrodes 5 A to 5 C guided out of the vacuum chamber 1 . The operating rods 16 A to 16 C are respectively coupled to these insulated operating rods in the air 14 A to 14 C.

Further, the ends of the movable electrodes 5 A to 5 C guided out of the vacuum chamber 1 are electrically connected with a conductor 25 . The connection is enabled by contact between a multi contact (collector) 41 provided in through holes in the conductor 25 for the movable electrodes 5 A to 5 C. The conductor 25 is fixed to the molded part 22 to be described later with a bolt 26 .

As shown in FIGS. 10 and 11 , earthing switches are connected to the fixed electrodes 9 B and 9 C in the respective main circuit switches. As shown in FIGS. 10 and 11 , the earthing switches have fixed side contact bases 39 B and 39 C and earthing switch movable electrodes 31 B and 31 C open/close to the fixed side contact bases 39 B and 39 C. The fixed side contact bases 39 B and 39 C are respectively connected to the fixed electrodes 9 B and 9 C via a conductor 38 C. The earthing switch movable electrodes 31 B and 31 C are guided with contact bases 40 B and 40 C having the multi contact (collector) 41 . Further, the fixed electrode 9 B of the main circuit switch is also connected, the same as the fixed electrodes 9 C.

In the present embodiment, the molded part 22 is formed on the periphery of the vacuum chamber 1 . As shown in FIG. 8 , the molded part 22 has the first insulating member 22 a to insulate the side of the fixed electrodes 9 A to 9 C of the main circuit switches and the bushing conductors 12 A to 12 C on the fixed electrode side, and the second insulating member 22 b , integrally formed with the first insulating member 22 a , to insulate the side of the movable electrodes 5 A to 5 C, the conductor 25 , the insulated operating rods in the air 14 A to 14 C, and the side of the movable operating rods 16 A to 16 C outside the respective vacuum chambers 1 .

More particularly, the first insulating member 22 a of the molded part 22 is an epoxy resin mold covering the lower peripheries of the respective vacuum chambers 1 and the peripheral surfaces of the busing conductors 12 A to 12 C on the fixed electrode side. The second insulating member 22 b is an epoxy resin mold, integrally formed with the epoxy rein mold as the first insulating member 22 a , surrounding the side of the movable operating rods 16 A to 16 C via the conductor 25 and the insulated operating rods in the air 14 A to 14 C. An earthed layer is formed on the peripheral surface of the molded part 22 .

Further, the contact base 40 C and the fixed side contact base 39 C in the earthing switch are integrally molded with the above-described first insulating member 22 a of the molded part 22 .

A molded cover 23 is attached to the upper part of the second insulating member 22 b of the molded part 22 via a seal 24 . The molded cover 23 has through holes for the movable operating rods 16 A to 16 C. The through holes are provided with seals 24 .

Note that in the present embodiment, the earthing switches are respectively connected to the fixed electrodes 9 B and 9 C.

As described above, in the present embodiment, the respective main circuit switches are accommodated in individual vacuum chambers. These vacuum chambers are integrally molded with the first insulating member 22 a which is an epoxy resin mold. On the side of the movable electrodes 5 A to 5 C, the conductor 25 , the insulated operating rods in the air 14 A to 14 C and the movable operating rods 16 A to 16 C, the second insulating member 22 b integrally formed with the epoxy resin mold as the first insulating member 22 a is provided so as to surround these elements. Thus the side of the movable electrodes 5 A to 5 C, the conductor 25 and the side of the movable operating rods 16 A to 16 C are air-insulated.

According to the above-described embodiment of the vacuum switchgear of the present invention, the respective main circuit switches are accommodated in the individual vacuum chambers, and these vacuum chambers are integrally molded with the first insulating member 22 a which is an epoxy resin mold. On the side of the movable electrodes 5 A to 5 C, the conductor 25 , the insulated operating rods in the air 14 A to 14 C and the movable operating rods 16 A to 16 C, the second insulating member 22 b integrally formed with the epoxy resin mold as the first insulating member 22 a is provided so as to surround these elements. Thus, as the side of the movable electrodes 5 A to 5 C, the conductor 25 and the side of the movable operating rods 16 a to 16 C are air-insulated, a multi circuit type vacuum switchgear with further improved ground isolation reliability can be provided.

Further, in the present embodiment as the conductor 25 having the multi contact (collector) 41 is fixed on the movable side, an electromagnetic repel force can be received by the conductor 25 , thereby the electromagnetic repel force applied to movable side electrode can be reduced. Further, in comparison with the case where the plural main circuit switches are accommodated in one vacuum chamber, the vacuum chambers can be downsized. As a result, the unit costs of the parts and the production cost can be reduced, and the entire cost can be greatly reduced.

Further, in the present embodiment, as shown in FIG. 11 , in the earthing switch, an earthing switch chamber 42 and an earthing switch chamber 43 may be molded so as to be closely provided to each other. In this structure, as the space in the earthing switch is reduced, the amount of mold can reduced, thus the original cost can be reduced.

FIG. 12 is a longitudinal back view showing another embodiment of the vacuum switchgear according to the present invention shown in FIGS. 8 to 11 . In FIG. 12 , as the elements having the same reference numerals as those in FIGS. 4 to 11 are the same elements, the detailed explanations of the elements will be omitted.

In this embodiment, the earthing switch chamber 43 in the earthing switch is wide.

According to the present embodiment, as the pressure change in the earthing switch chamber 43 which occurs upon vertical motion of the earthing switch movable electrode 31 can be suppressed, it is easy to seal with the seal 24 , and the reliability can be improved.

FIG. 13 is a longitudinal back view showing another embodiment of the vacuum switchgear according to the present invention shown in FIGS. 8 to 11 . In FIG. 13 , as the elements having the same reference numerals as those in FIGS. 4 to 12 are the same elements, the detailed explanations of the elements will be omitted.

In the present embodiment, communication grooves 44 B and 44 C for communication between the earthing switch chambers and the ambient air side are respectively provided on the side surfaces of the earthing switch movable electrodes 31 B and 31 C. The communication grooves 44 B and 44 C prevent condensation in the earthing switch chambers by communicating the earthing switch chambers with the ambient air side, only upon interruption operation and actuation operation of the earthing switches.

Note that in the embodiment shown in FIGS. 8 to 13 , the air insulated type earthing switch is shown, however, the vacuum insulated type earthing switch as shown in FIG. 5 is applicable. Further, the vacuum insulated type earthing switch in the embodiment shown in FIG. 5 may be replaced with the air insulated type earthing switch.