NZ732949A - Vacuum circuit breaker - Google Patents

Abstract

vacuum circuit breaker (1) has: a grounding tank (2); vacuum interrupters (3, 4); a linking mechanism (5) for opening and closing the vacuum interrupters (3, 4); and a linking mechanism case (19) for accommodating the linking mechanism (5). A support porcelain tube (21) for supporting the linking mechanism case (19) is provided on the inner peripheral surface of the grounding tank (2), and an insulated operating rod (20) for operating the linking mechanism (5) is provided so as to pass through the inside of the support porcelain tube (21) and a side part of the grounding tank (2). An operating chamber (23) is provided in the passage for the insulated operating rod (20) in the grounding tank (2), and a conversion mechanism (24) for driving the insulated operating rod (20) is accommodated within the operating chamber (23). A space (within the linking mechanism case (19), within the support porcelain tube (21), and the like) linked with the inside peripheral part of bellows (13, 13) for the vacuum interrupters (3, 4) is filled with insulating gas at 0.3 MPa or less, and other spaces are filled with high pressure insulating gas. mechanism case (19) is provided on the inner peripheral surface of the grounding tank (2), and an insulated operating rod (20) for operating the linking mechanism (5) is provided so as to pass through the inside of the support porcelain tube (21) and a side part of the grounding tank (2). An operating chamber (23) is provided in the passage for the insulated operating rod (20) in the grounding tank (2), and a conversion mechanism (24) for driving the insulated operating rod (20) is accommodated within the operating chamber (23). A space (within the linking mechanism case (19), within the support porcelain tube (21), and the like) linked with the inside peripheral part of bellows (13, 13) for the vacuum interrupters (3, 4) is filled with insulating gas at 0.3 MPa or less, and other spaces are filled with high pressure insulating gas.

Description

DESCRIPTION Title of the Invention VACUUM CIRCUIT BREAKER Field of the Invention The present invention relates to a vacuum circuit breaker and, more particularly, to an internal pressure structure of a double—break vacuum circuit breaker.

Background Alt Vacuum circuit breakers (VCB) are Widely used for power systems, notably —voltage class power systems of 84 kV or lower. The vacuum circuit r is advantageous to other circuit breakers (such as gas circuit breaker (GCB)) in that: a breaker part of the vacuum t breaker is long in lifetime; the amount of high-global-warming—potential gas (e.g. SFs gas) used in the vacuum circuit breaker is small; and the vacuum circuit breaker is low in life cycle cost (LCC) because of easy I5 recovery and recycling of SR gas. The vacuum t breaker of tank type, which has a vacuum interrupter (VI) covered by a ground layer, is low in gravity center and is advantageous to conventional insulator type breakers in that: it is easier to mount a t ormer to the tank type vacuum circuit breaker; and the tank type vacuum circuit breaker is improved in earthquake ance.

[0003] Various proposals have recently been made to obtain high-voltage high-capacity vacuum circuit breakers for expanded uses of the vacuum circuit breakers (see, for e, Non-Patent Document 1). In one proposed high—voltage vacuum circuit breaker, two vacuum upters as breaker parts are connected in series so as to improve withstand voltage performance.

[0004] is a vertical sectional front View of a vacuum t breaker 35 according to such conventional technology. This vacuum circuit breaker 35 includes a ground tank 2, vacuum interrupters 3 and 4 accommodated in the ground tank 2, and a link mechanism for opening and closing the vacuum interrupters 3 and 4.

The ground tank 2 is in the form of a cylindrical metallic container in which the vacuum intenupters 3 and 4 and the link mechanism 5 are accommodated. The inside of the ground tank 2 is filled with insulating gas such as SF6 gas.

In the vacuum inteirupter 3, a pair of electrodes (a fixed electrode 7 and a movable electrode 8) are placed in a vacuum vessel 6 which is constituted by an ting tube and a metallic flange. An ediate shield 9 is disposed within the vacuum vessel 6 so as to cover the fixed electrode 7 and the movable electrode 8. The fixed ode 7 is fixed to one end portion of a fixed lead 3a. The other end portion of the fixed lead 3a protiudes from an end face of the vacuum vessel 6 and is fixed to a support insulating member 10. A conductor 12 is coupled to the other end portion of the fixed lead 3a via a metallic conductor fitting ll. The movable ode 8 is fixed to one end n of a movable lead 3b. The other end portion of the movable lead 3b protmdes from an end face of the vacuum vessel 6 and is coupled to the link mechanism 5. A bellows 13 is disposed on a part of the movable lead 3d inserted within the vacuum vessel 6 so as to allow axial movement of the movable lead 3b while maintaining the vacuum inside the vacuum vessel 6. A e—dividing capacitor 14 is arranged in parallel with the vacuum interrupter 3.

The vacuum interrupter 4 is similar in ration to the vacuum inten'upter 3.

In the vacuum interrupter 4, a pair of electrodes (a fixed electrode 7 and a movable electrode 8) are placed in a vacuum vessel 6. The fixed electrode 7 is fixed to one end portion of a fixed lead 4a. The other end portion of the fixed lead 4a is fixed to a suppo1t insulating member 15. A conductor 17 is d to the other end portion of the fixed lead 4a via a metallic conductor fitting 16. The movable electrode 8 is fixed to one end portion of a movable lead 4b. The other end n of the movable lead 4b protrudes from an end face of the vacuum vessel 6 and is coupled to the link mechanism 5. A voltage—dividing capacitor 18 is arranged in parallel with the vacuum interrupter 4.

The link mechanism 5 is provided with a link member 5a, a link member 5b and link members Sc, and is placed in a link mechanism case 36. One end n of the link member 5a is rotatably supported in the link mechanism case 36; and the other end portion of the link member 5a is rotatably supported on the movable lead 3b. One end portion of the link member 50 is rotatably disposed on the link member 5a; and the other end portion of the link member Sc is rotatably supported on one end portion of an insulating operation rod 20, which is used for opening/closing operations of the vacuum interrupters 3 and 4.

Similarly, one end portion of the link member 5b is rotatably supported in the link mechanism case 36; and the other end portion of the link member Sb is rotatably supported on the movable lead 4b. One end portion of the link member 5c is rotatably supported on the link member 5b; and the other end portion of the link member Sc is rotatably supported on the one end portion of the ting operation rod 20.

The link mechanism case 36 is shaped to house therein the link mechanism 5 and to provide electrical connection between the movable lead 3b and the movable lead 4b.

The link mechanism case 36 is an‘anged between a movable—side end portion of the vacuum inteirupter 3 (from which the movable lead 3b protludes) and a movable—side end portion of the vacuum interrupter 4 (from which the movable lead 4b protrudes). The link mechanism case 36 is supported by an insulating support tube 21 which is disposed on an inner circumferential surface of the ground tank 2.

[0010] The insulating operation rod 20 is inserted and passes h the link mechanism case 36, the insulating support tube 21 and a side portion of the ground tank 2.

Further, an operation room 23 is provided on an outer circumference of the p01tion of the ground tank 2 through which the insulating operation rod 20 is inserted.

A conversion ism 24 for converting rotation of a rotation shaft 25 to linear movement of the insulating operation rod 20 is arranged in the operation room 23.

One end portion of the rotation shaft 25 is exposed outside from the operation room 23 through a onal seal 26. An operation ism (not shown) for operating the insulating operation rod 20 and a drive unit for driving an insulating operation rod of another phase are coupled to the rotation shaft 25 at positions outside the operation room 23.

In the vacuum t breaker 35, the insides of the ground tank 2, the link ism case 36, the insulating support tube 21 and the ion room 23 are filled with insulating gas so as to insulate the high-voltage parts such as the conductors 12 and 17, the fixed— and movable-side end portions of the vacuum interrupters 3 and 4 and the link mechanism case 36 from the ground tank 2 of ground potential. For example, SFG gas of about 0.25 MPa is used as the inSulating gas. The SFG gas has good insulation ties and can perform its function at a low pressure. The vacuum circuit breaker 35 has a double~break structure in which the vacuum upters 3 and 4 as breaker parts are ted in series and thus shows a high withstand voltage for use in high voltage applications.

In the above stiucture, input Operation is executed when the ting operation rod 20 is moved in a direction toward the inside of the ground tank 2 (i.e. an upward direction in the figure) by rotation of an unillustrated lever, which is d to a drive unit 27, in response to an input command. As the insulating operation rod 20 is moved, the link Sc coupled to the link 5a moves upward while turning right. With this movement of the link So, the link 5a moves the movable lead 3b along the axis in a direction toward the vacuum interrupter 3. The fixed electrode 7 and the movable electrode 8 of the vacuum interrupter 3 are consequently connected to each other. Similarly, the link Sc coupled to the link 5b moves upward while turning left as the insulating ion rod 20 is moved.

With this movement of the link So, the link 5b moves the movable lead 4b along the axis in a direction toward the vacuum interrupter 4. The fixed electrode 7 and the e electrode 8 of the vacuum interrupter 4 are consequently connected to each other. r, breaking operation is executed when the insulating operation rod 20 is moved in a direction toward the outside of the ground tank 2 (i.e. a rd direction in the figure). By the reverse action to that in the input operation, the movable lead 3b moves along the axis in a direction apart from the vacuum interrupter 3 so that the fixed electrode 7 and the movable electrode 8 of the vacuum interrupter 3 are separated from each other. The e lead 4b also moves along the axis in a direction apart from the vacuum interrupter 4 so that the fixed electrode 7 and the movable electrode 8 of the vacuum intenupter 4 are separated from each other.

In the vacuum intenupters 3 and 4, the vacuum in the vacuum vessel 6 is maintained by the able and contractible s 13 even when the movable lead 3b, 4b moves during the input and breaking operations. The bellows 13 is thus structured to bear a pressure difference to some extent between the vacuum on the outer side and the pressure of the insulating gas on the inner side.

However, the bellows 13 is made of a thin metal material of e.g. stainless. steel and suffers a phenomenon called buckling when the pressure difference becomes larger than or equal to a certain level. For this reason, the pressure of the insulating gas on the inner side of the s needs to be lower than or equal to about 0.3 MPa. , although it is conceivable to increase the pressure of the insulating gas filled in the vacuum circuit breaker and thereby e the insulation performance of the vacuum circuit breaker for use in higher voltage applications, the bellows becomes one of the weakest points in the vacuum upter due to such a gas pressure increase.

It has thus been studied to provide the bellows with a structure capable of bearing a re ence between the inner and outer sides thereof (e.g. external pressure type bellows) (see, for example, Non-Patent Document 2). The material and ure of the bellows used in the high pressure resistant vacuum interrupter are however special and can become a cause of cost increase of the vacuum circuit breaker. Further, the use of the external pressure type bellows can lead to an upsizing of the s part and a deterioration of the heat dissipation performance of the vacuum interrupter.

As to a single-break tank-type vacuum circuit breaker, it has been ed to fill the insulating support tube, which is not in communication with the inner side of the bellows, with high pressure dry air and set the inner side of the bellows to an atmospheric pressure for the purpose of preventing bucking of the s while preventing global warming (see, for example, Patent Document 1).

Prior Art nts Patent Documents Patent Document 1: Japanese Laid-Open Patent Publication No. 2007-306701 Non-Patent Documents Non—Patent Document 1: Kazuhiro NAGATAKE and Four Others, “Development of 168 kV 40 kA 2-point Breaking Type Vacuum Circuit Breaker”, dings of Heisei 17 Annual Conference of Power and Energy Society, Institute of Electrical Engineering of Japan, 2005, N0. 319, pp. 38-3, 38-4 Non—Patent Document 2: Kazuhiro NAGATAKE and Five Others, “Development of Environmentally Benign Type 72/84 kV Vacuum Circuit Breaker”, dings of Heisei 15 Annual Conference of Power and Energy Society, Institute of Electrical Engineering of Japan, 2003, No. 237, pp. 8—143, 8—144 Summaly of the Invention

[0022] It is an object of the present invention to provide a technique for contributing to high voltage applications of a double—break vacuum circuit breaker.

To achieve the above object, there is provided according to the present invention a vacuum circuit breaker, comprising: first and second vacuum interrupters each : a vacuum vessel with an insulating tube and a ic flange; fixed and movable electrodes placed in the vacuum vessel; a movable lead supporting the movable electrode such that the movable electrode can be brought into contact with or separated from the fixed electrode; and a bellows diSposed On a part of the movable lead inserted within the vacuum vessel; a ground tank that odates the first vacuum interrupter and the second vacuum interrupter; a link ism arranged in the ground tank so as to move the movable lead of the first vacuum interrupter and the movable lead of the second vacuum interrupter in an axial direction; a link mechanism case that houses the link mechanism; an insulating support tube disposed on an inner circumferential surface of the ground tank and supporting the link mechanism case; and an insulating operation rod coupled to the link mechanism so as to cause operation of the link mechanism, wherein the movable lead of the first vacuum interrupter is inserted in the link mechanism case so as to allow communication between an inside of the link mechanism case and an imier side of the bellows of the first vacuum interrupter through a n of the link case mechanism in which the movable lead of the first vacuum interrupter is inserted; wherein the movable lead of the second vacuum interrupter is inserted in the link mechanism case so as to allow communication between the inside of the link mechanism case and an inner side of the bellows of the second vacuum interrupter through a portion of the link case mechanism in which the movable lead of the second vacuum interrupter is inserted; wherein the insulating operation rod is inserted through an inside of the insulating support tube and through a side portion of the ground tank; n the inner side of the bellows of the first vacuum interrupter, the inner side of the bellows of the second vacuum interrupter, the inside of the link ism case and the inside of the insulating support tube communicate with one another to define a communication space; wherein the communication space is hermetically isolated from a space inside the ground tank and outside the link mechanism case and the insulating support tube; wherein the space communicating with the inner side of the bellows of the first vacuum interrupter and the inner side of the bellows of the second vacuum interrupter is filled with insulating gas of 0.3 MPa or lower; and wherein the space inside the ground tank and outside the link mechanism case and the insulating t tube is filled with ting gas of higher re than that of the insulating gas in the space communicating with the inner side of the bellows of the first vacuum interrupter and the inner side of the s of the second vacuum interrupter.

Brief Description of the Drawings is a sectional view of a vacuum t breaker according to one embodiment of the present invention. is an enlarged sectional View of a principal part of the vacuum circuit breaker according to the one ment of the present invention. is an enlarged sectional View of a pal part of a vacuum circuit breaker according to another embodiment of the present invention. is a sectional View of a vacuum circuit breaker according to the conventional technology. ption of the Embodiments A vacuum circuit breaker according to one embodiment of the t invention will be described below with reference to the drawings. It should be understood that: the drawings are intended to schematically Show the vacuum t breaker according to one embodiment of the present invention; and the dimensions of the respective parts and portions in the drawings may be exaggerated for illustration es.

FIG. I is a vertical sectional front view of a vacuum circuit breaker l according to one embodiment of the present invention. The vacuum circuit breaker 1 includes a ground tank 2, vacuum intenupters 3 and 4 accommodated in the ground tank 2, and a link mechanism 5 for opening and closing the vacuum interrupters 3 and 4.

The ground tank 2 is in the form of a cylindrical metallic container in which the vacuum interrupters 3 and 4 and the link mechanism 5 are accommodated. The inside of the ground tank 2 is filled with insulating gas such as SF(, gas.

[0028] In the vacuum interrupter 3, a pair of electrodes (21 fixed electrode 7 and a movable ode 8) are placed in a vacuum vessel 6 which is constituted by an insulating tube and a metallic flange. An intermediate shield 9 is disposed within the vacuum vessel 6 so as to cover the fixed electrode 7 and the e electrode 8. The fixed electrode 7 is fixed to one end n of a fixed lead 3a. The other end portion of the fixed lead 3a protrudes from an end face of the vacuum vessel 6 and is fixed to a support insulating member 10. A conductor 12 is coupled to the other end portion of the fixed lead 3a via a metallic conductor fitting ll. The movable electrode 8 is fixed to one end portion of a movable lead 3b. The other end portion of the movable lead 3b des from an end face of the vacuum vessel 6 and is coupled to the link mechanism 5. A bellows 13 is disposed on a part of the movable lead 3d ed within the vacuum vessel 6 so as to allow axial movement of the movable lead 3b while maintaining the vacuum inside the vacuum vessel 6. A voltage—dividing capacitor 14 is arranged in parallel with the vacuum interrupter 3.

The vacuum interrupter 4 is similar in configuration to the vacuum interrupter 3.

In the vacuum upter 4, a pair of electrodes (a fixed electrode 7 and a movable electrode 8) are placed in a vacuum vessel 6. The fixed electrode 7 is fixed to one end portion of a fixed lead 4a. The other end portion of the fixed lead 4a is fixed to a support insulating member 15. A conductor 17 is coupled to the other end p01tion of the fixed lead 4a via a metallic conductor fitting 16. The movable electrode 8 is fixed to one end portion of a movable lead 4b. The other end portion of the movable lead 4b protrudes from an end face of the vacuum vessel 6 and is coupled to the link mechanism 5. A voltage-dividing capacitor 18 is arranged in parallel with the vacuum interrupter 4.

The link mechanism 5 is provided with a link member 5a, a link member 5b and link members Sc, and is placed in a link ism case 19. One end portion of the link member 5a is rotatably supported in the link mechanism case 19; and the other end portion of the link member 5a is rotatably coupled to the movable lead 3h. One end portion of the link member Sc is rotatably disposed on the link member 5a; and the other end portion of the link member 5c is rotatably supported on one end portion of an insulating operation rod 20, which is used for opening/closing operations of the vacuum interrupters 3 and 4.

Similarly, one end ponion of the link member 5b is rotatably supported in the link mechanism case 19; and the other end portion of the link member 5b is rotatably coupled to the movable lead 413. One end n of the link member 5c is rotatably supported on the link member 5b; and the other end portion of the link member Se is bly supported on the one end portion of the insulating operation rod 20.

The link ism case 19 is shaped to house therein the link mechanism 5 and to e electrical connection between the movable lead 3b and the e lead 4b.

The link mechanism case 19 is arranged between a movable—side end portion of the vacuum interrupter 3 (from which the movable lead 3b protiudes) and a movable-side end portion of the vacuum interrupter 4 (from which the movable lead 4b protrudes). The link mechanism case 19 is supported by an insulating support tube 21 which is ed on an inner circumferential e of the ground tank 2.

[0032] As shown in the link mechanism case 19 and the movable-side end portion 3c of the vacuum interrupter 3 are ically connected to each other by a packing such as O—ring (not shown). The movable lead 3b is inse1ted in the link mechanism case 19. The inner side of the s 13 of the vacuum interrupter 3 is in communication with the inside of the link mechanism case 19 through the n 193 of the link mechanism case 19 in which the movable lead 3b is inserted. A connection part 22 such as ring c0ntact is provided in the lead insertion portion 19a so as to provide electrical connection between the movable lead 3b and the link mechanism case 19.

Similarly, the link mechanism case 19 and the movable-side end portion 40 of the vacuum upter 4 are hermetically connected to each other by a packing such as O—ring (not shown). The movable lead 4b is inserted in the link mechanism case 19. The inner side of the bellows 13 of the vacuum interrupter 4 is in ication with the inside of the link mechaniSm case 19 through the portion l9b of the link mechanism case 19 in which the movable lead 4b is inserted. A connection part 22 such as ring contact is also provided in the lead insertion n 19b so as to provide ical connection n the movable lead 4b and the link mechanism case 19. A manhole 190 is formed in an upper portion of the link mechanism case 19 for placement of the link mechanism 5 in the link mechanism case 19. The manhole 190 is sealed with a seal member 19d.

As shown in the insulating support tube 21 is disposed on the inner circumferential n of the ground tank 2 so as to support the link mechanism case 19.

A connection part between the insulating support tube 21 and the link mechanism case 19 and a connection part between the insulating support tube 21 and the ground tank 2 are hermitically sealed by packings such as O-rings The insulating operation rod 20 is ed and passes through the link mechanism case 19, the inside of the insulating support tube 21 and a side n of the ground tank 2. Further, an operation room 23 is provided on an outer circumferential side of the portion of the ground electrode 2 through which the insulating operation rod 20 is inserted.

The operation room 23 isvhennetically sealed to the outer circumferential side of the ground tank 2 by a packing such as O-ring. A conversion mechanism 24 is arranged in the operation room 23 and configured to convert rotation of a rotation shaft (rotation drive shaft) 25 to linear movement of the insulating operation rod 20. One end portion of the rotation shaft 25 is exposed outside from the operation room 23 through a rotational seal 26 (e.g. a rotational seal casing sealed with a hydraulic packing such as SKY packing).

An operation ism (not shown) for ing the insulating Operation rod 20 and a drive unit 27 for g an insulating operation rod of another phase are d to the rotation shaft 25 at ons Outside the operation room 23. In the operation room 23, there are also provided a pressure gauge for monitoring the pressure inside the operation room 23, a valve for ing the pressure inside the operation room 23 and the like although not shown in the drawings.

The conductor 12 is arranged to protrude from the ground tank 2. A bushing 28 is disposed around the conductor 12 and supported by the ground tank 2. A g terminal 28a is provided on an upper end n of the bushing 28. A bushing current transformer 29 is provided in a connection part between the bushing 28 and the ground tank 2. Similarly, the conductor 17 is arranged to protrude from the ground tank 2. A bushing 30 is disposed around the conductor 17 and supported by the ground tank 2. A g terminal 30a is provided on an upper end portion of the bushing 30. A bushing current transformer 31 is provided in a connection part between the bushing 30 and the ground tank 2.

[0037] In the above-structured vacuum circuit breaker 1, the inner side of the bellows 13 of the vacuum intenupter 3, the inner side of the s 13 of the vacuum interrupter 4, the inside of the link mechanism case 19, the inside of the insulating support tube 21 and the inside of the operation room 23 are in communication with one another to define a sealed communication space. This space is filled with insulating gas of 0.3 MPa or lower (for e, SFs gas of 0.25 MPa). The diagonally shaded area in corresponds to the space filled with such low pressure insulating gas. On the other hand, a space inside the ground tank 2 and the bushings 28 and 30 is filled with high pressure insulating gas (for example, SFs gas of higher pressure than that on the inner side of the bellows 13 of the vacuum inten‘upter 3 and on the inner side of the bellows 13 of the vacuum interrupter 4).

[0038] The low—pressure—side space (which is in communication with the inner sides of the bellows 13 of the vacuum intenupters 3 and 4) and the high-pressure—side space (which is isolated from and not in communicatiou with the imier sides of the bellows 13) may be filled with insulating gas other than SF6 gas, such as dry air, nitrogen gas (N2) or carbon dioxide gas (C02).

[0039] . For case of maintenance of the vacuum circuit breaker 1, it is preferable to fill the low—pressure-side space and the high~pressure—side space with the same kind of insulating gas. In the case of filling the low-pressure-side space and the high-pressure-side space with SFe gas, for example, the higher the pressure of the SR gas in the high—pressure—side space, the more improved the insulation perfontnance of the vacuum circuit breaker 1. This leads to downsizing of the vacuum circuit r 1. In the case of filling the low—pressure—side space and the high—pressure—side space with dry air, the insulation performance tends to be lowered as compared with the case of SF5 gas. It is however possible to compensate for the lowered insulation performance by increasing the pressure of the dry air filled in the high-pressure—side space. In this case, the lowered insulation perfonnance in the low-pressure-side space can be compensated for by e.g. increasing the distance n the high—voltage part and the ground potential part.

[0040] By filling the low—pressure—side space and the high—pressure—side space with different kinds of insulating gases, the vacuum circuit breaker 1 can be obtained so as to comply with prevention of global warming without upsizing of the vacuum circuit breaker 1. In the case of filling the low-pressure-side space with SF5 gas and filling the ressure—side space with dry air, for example, it is possible to ss the amount of use of the SR gas and suppress ng of the vacuum circuit breaker 1.

Next, an explanation will be given of input and breaking operations of the vacuum circuit breaker l. The input and breaking ions of the vacuum circuit breaker l are actuated with operation of the link mechanism 5 by the insulating operation rod 20. Since the rotational seal 26 is provided in the rotation shaft 17 insertion portion of the operation room 23 in the vacuum circuit r 1, the input operation (or breaking operation) of the vacuum t breaker 1 is executed by operating the insulating operation rod 20 in the state where the pressure inside the operation room 23 (i.e. the pressure on the inner sides of the bellows 13) is maintained at a low pressure of 0.3 MPa.

The input ion of the vacuum t breaker 1 is executed by the action of the link mechanism 5 when the insulating operation rod 20 is moved in a direction toward the inside of the ground tank 2 (an upward direction in the figure). As the insulating operation rod 20 is moved, the link Sc coupled to the link 5a moves upward while turning right. With this movement of the link Sc, the link 5a moves the movable lead 3b along the axis in a direction toward the vacuum interrupter 3. The fixed electrode 7 and the movable electrode 8 of the vacuum interiupter 3 are consequently brought into contact with and connected to each other. rly, the link Sc d to the link 5b moves upward while turning left as the insulating operation rod 20 is moved. With this movement of the link 5c, the link 5b moves the movable lead 4b along the axis in a direction toward the vacuum interrupter 4. The fixed electrode 7 and the movable electrode 8 of the vacuum interrupter 4 are consequently brought into contact with and connected to each other.

The ng operation is executed by the action of the link mechanism 5 when the insulating ion rod 20 is moved in a direction toward the outside of the ground tank 2 (a downward directiOn in the figure). By the reverse action to that in the input operation, the movable lead 3b moves along the axis in a ion apart from the vacuum interrupter 3 so that the fixed electrode 7 and the movable electrode 8 of the vacuum interrupter 3 are separated from each other. The movable lead 4b also moves along the axis in a direction apart from the vacuum interrupter 4 so that the fixed electrode 7 and the movable electrode 8 of the vacuum interrupter 4 are separated from each other.

In the vacuum circuit breaker 1 according to the above embodiment of the t invention, it is possible to suppress damage on the bellows 13 by setting the pressure of the insulating gas on the inner sides of the bellows 13 of the vacuum interrupters 3 and 4 to be 0.3 MPa or lower and thereby reducing the pressure difference between the iimer and outer sides of the bellows l3. It is further possible to improve the insulation performance of the vacuum circuit breaker l for use in high voltage application by increasing the pressure of the insulating gas in the space not communicating with the inner sides of the bellows l3 (e.g. the space inside the ground tank 2 and outside the link mechanism case 19 and the insulating support tube 21). For example, dry air of about 0.6 MPa is usable in the case of the vacuum t r with high pressure ant vacuum intenupters. Hence, the pressure of the insulating gas in the space not communicating with the inner sides of the bellows 13 is set higher than the pressure of the insulating gas in the space in communication with the inner sides of the bellows 13, ably higher than 0.3 MPa, more preferably 0.6 to 0.8 MPa, in order to improve the insulation perfonnance of the vacuum circuit breaker 1 without upsizing of the vacuum circuit breaker l.

Heretofore, double—break vacuum t breakers have been used mainly in the medium e class. Not many considerations have been made about high voltage applications of vacuum circuit breakers. By st, the above-stmctured double-break vacuum circuit breaker 1 according to the present invention is improved in insulation performance and le for higher voltage applications. It is accordingly possible to expand the range of uses of the vacuum circuit breaker 1 up to the higher voltage class (e.g. 84 kV or higher voltage . In View of the usage of a vacuum circuit breaker with a single vacuum upter as a vacuum circuit breaker of 145 kV voltage class, it is vable that the range of uses of the double-break vacuum circuit breaker could be expanded up to 300 kV or higher voltage class.

Because of the high global warming potential of the SF6 gas, it is required to minimize the amount of use of the SFG gas for prevention of global warming.

Considerations have been made to the use of dry air, which is substantially zero in global warming potential and effective for prevention of global warming, and other insulating gases such as nitrogen gas (N2), carbon dioxide gas (C02) etc. as alternatives to the SF6 gas.

The tion ties of these ative gases are inferior to those of the SF5 gas.

Thus, the pressure of the alterative gas filled in the vacuum circuit breaker needs to be increased to about 0.5 to 0.6 MPa for insulation performance improvement. Due to such a gas pressure se, however, the bellows 13 of the vacuum upter 3 (or the bellows 13 of the vacuum interrupter 4) may be damaged. More specifically, in the conventional vacuum circuit breaker 35 of the introduction of high pressure insulating gas to the inside of the ground tank 2 leads to the introduction of high pressure insulating gas to the space communicating with the inner side of the bellows 13. As a result, there arises a large pressure difference between the vacuum on the outer side of the bellows l3 and the high pressure on the imier side of the bellows 13 so that the bellows 13 may be damaged due to the large pressure difference. In the case of decreasing the pressure of the insulating gas introduced to the ground tank 2 for suppression of damage on the bellows 13, the distance between the high—voltage part and the ground potential part (e.g. between the link mechanism case 26 and the ground tank 2 becomes increased to compensate for the lowered insulation performance. This ce se causes upsizing of the vacuum circuit breaker 35.

On the other hand, the vacuum circuit breaker 1 according to the above embodiment of the present invention has a structure lled double—pressure-chamber stlucture) in which: the space communicating with the ilmer sides of the bellows is filled with the low pressure insulating gas; and the other insulation space is filled with the high pressure insulating gas. By the adOption of such a structure, it is possible to suppress damage on the bellows 3 and e the insulation performance of the vacuum circuit breaker 1. For example, by filling the high—electric-field space such as the space between the link mechanism case 19 and the ground tank 2 with high-pressure dry air, the use of the high—global—wanning—potential insulating gas is suppressed, without impairment of the insulation performance, so as to contribute to tion of global warming.

Furthennore, the bellows 13 does not need to be provided with a structure capable of bearing a pressure difference between the inner and outer sides thereof in the vacuum circuit breaker 1 according to the above embodiment of the present invention. A mass—produced type bellows can be utilized for cost reduction of the vacuum intenupter 3, 4. The utilization of such an ordinary internal re type bellows allows use of an operation unit having a small self—closing force and small operating force. It is ingly possible to manufacture the vacuum t breaker l at a low cost, without using special high pressure resistant vacuum interrupters, and ss upsizing of the vacuum circuit breaker l.

[0049] The end portion of the rotation shaft 15 of the conversion mechanism 14, which is used for operation of the insulating operation rod 20‘, is exposed outside the operation room 23 through the rotational seal 26. The on shaft 15 is thus ed while maintaining hermeticity. In other words, by ing one hermetic seal to the insulating operation rod 2, the opening and closing operations of the vacuum interrupters 3 and 4 are executed in the state where the inner sides of the bellows 13 of the vacuum interrupters 3 and 4 are kept hermetically sealed. Since one hermetical sliding part is provided in the vacuum circuit breaker, it is possible to reduce the number of components of the vacuum circuit breaker l and improve the reliability of the vacuum circuit breaker l as compared to the case of respectively maintaining hermetic seals on the movable parts of the vacuum interrupters 3 and 4. [005 0] It should be understood that: the vacuum circuit breaker according to the t invention is not limited to the above-described embodiment; s changes and modification of the embodiment described above can be made within the range that does not impair the es of the present invention; and all such changes and modifications fall Within the scope of the present invention.

For example, it is feasible to arrange a linear seal 32 in the p01tion of the ground tank 2 through which the insulating ion rod 20 is inserted as shown in More specifically, the linear seal 32 is provided by disposing a ground-side fitting 33 on a portion of the insulating operation rod 20 which is inserted h the ground tank 2 ing a housing 34 in the portion of the ground tank 2 through which the insulating operation rod 20 is inserted. For opening or closing of the vacuum interrupters 3 and 4, the insulating operation rod 20 makes sliding movement in the direction toward the inside or e of the ground tank 2 while maintaining hermeticity n the outer side of the ground—side fitting 33 and the inner side of the housing 34. The insulating operation rod is thus Operated in the state where the inside of the insulating support tube 21 is kept hermetically sealed. By arranging such a linear seal 32 in the portion of the ground tank 2 through which the insulating operation rod 20 is inserted, the space filled with the low pressure insulating gas is fiirther ed so that it is possible to obtain a further reduction in the amount of the ting gas filled in the space communicating with the inner sides of the bellows 13 as well as the effects of the vacuum circuit breaker 1 according to the above ment.

[0052] Although the above embodiment specifically refers to the vacuum circuit breaker 1 in which the movable lead 3b of the vacuum interrupter 3 and the movable lead 4b of the vacuum intenupter 4 are arranged coaxially with each other, the t invention is also applicable to a vacuum circuit breaker of the type in which the movable lead 3b and the movable lead 4b are arranged at an acute angle to each other or in which the movable lead 3b and the movable lead 4b are arranged in parallel with each other.

Claims (2)

1. A vacuum circuit breaker, comprising: first and second vacuum interrupters each : a vacuum vessel with an insulating tube and a metallic flange; fixed and movable electrodes placed in the vacuum vessel; a movable lead supporting the movable ode such that the movable electrode can be t into contact with or separated from the fixed electrode; and a bellows disposed on a part of the movable lead inserted within the vacuum ; a ground tank that odates the first vacuum interrupter and the second vacuum interrupter; a link mechanism arranged in the ground tank so as to move the movable lead of the first vacuum interrupter and the movable lead of the second vacuum interrupter in an axial direction; a link mechanism case that houses the link mechanism; an insulating support tube disposed on an inner circumferential surface of the ground tank and supporting the link mechanism case; an insulating operation rod coupled to the link mechanism so as to cause operation of the link mechanism; and an operation room provided on an outer side of the portion of the ground tank through which the insulating operation rod is ed, such that the operation room is in communication with the inside of the insulating support tube, wherein the movable lead of the first vacuum interrupter is inserted in the link mechanism case so as to allow communication between an inside of the link mechanism case and an inner side of the bellows of the first vacuum interrupter through a portion of the link case mechanism in which the e lead of the first vacuum upter is inserted; wherein the movable lead of the second vacuum interrupter is inserted in the link mechanism case so as to allow communication between the inside of the link mechanism case and an inner side of the bellows of the second vacuum interrupter through a portion of the link case mechanism in which the e lead of the second vacuum interrupter is inserted; wherein the insulating operation rod is inserted through an inside of the insulating 9154982_1 (GHMatters) P105329.NZ support tube and through a side portion of the ground tank; wherein a rotation drive shaft is coupled to the insulating operation rod within the operation room; n one end portion of the rotation drive shaft is exposed outside from the operation room h a onal seal; wherein the inner side of the bellows of the first vacuum interrupter, the inner side of the bellows of the second vacuum interrupter, the inside of the link mechanism case and the inside of the ting t tube communicate with one another to define a communication space; wherein the communication space is ically isolated from a space inside the ground tank and outside the link mechanism case and the insulating support tube; wherein the space communicating with the inner side of the bellows of the first vacuum interrupter and the inner side of the bellows of the second vacuum interrupter is filled with insulating gas of 0.3 MPa or lower; and wherein the space inside the ground tank and outside the link mechanism case and the insulating support tube is filled with insulating gas of higher pressure than that of the insulating gas in the space communicating with the inner side of the bellows of the first vacuum interrupter and the inner side of the bellows of the second vacuum interrupter.

2. A vacuum circuit breaker, comprising: first and second vacuum interrupters each having: a vacuum vessel with an insulating tube and a metallic flange; fixed and movable electrodes placed in the vacuum vessel; a movable lead supporting the movable electrode such that the movable electrode can be brought into contact with or separated from the fixed electrode; and a bellows disposed on a part of the e lead inserted within the vacuum vessel; a ground tank that accommodates the first vacuum interrupter and the second vacuum interrupter; a link mechanism arranged in the ground tank so as to move the movable lead of the first vacuum upter and the movable lead of the second vacuum interrupter in an axial direction; a link mechanism case that houses the link mechanism; an insulating support tube disposed on an inner circumferential surface of the 9154982_1 ters) P105329.NZ ground tank and supporting the link ism case; and an insulating operation rod coupled to the link mechanism so as to cause operation of the link mechanism, wherein the movable lead of the first vacuum interrupter is inserted in the link mechanism case so as to allow communication between an inside of the link mechanism case and an inner side of the bellows of the first vacuum interrupter through a portion of the link case mechanism in which the movable lead of the first vacuum interrupter is inserted; wherein the movable lead of the second vacuum interrupter is inserted in the link mechanism case so as to allow communication between the inside of the link mechanism case and an inner side of the bellows of the second vacuum upter through a portion of the link case mechanism in which the movable lead of the second vacuum upter is inserted; wherein the insulating operation rod is inserted through an inside of the insulating support tube and through a side portion of the ground tank; wherein a linear seal is arranged in the portion of the ground tank through which the insulating operation rod is inserted; wherein the inner side of the bellows of the first vacuum interrupter, the inner side of the bellows of the second vacuum interrupter, the inside of the link mechanism case and the inside of the insulating support tube communicate with one another to define a communication space; wherein the communication space is ically ed from a space inside the ground tank and outside the link mechanism case and the insulating support tube; wherein the space communicating with the inner side of the bellows of the first vacuum interrupter and the inner side of the bellows of the second vacuum upter is filled with insulating gas of 0.3 MPa or lower; and wherein the space inside the ground tank and outside the link ism case and the insulating support tube is filled with insulating gas of higher pressure than that of the insulating gas in the space icating with the inner side of the bellows of the first vacuum interrupter and the inner side of the bellows of the second vacuum interrupter. 2_1 (GHMatters) P105329.NZ FIG. 4