Gas circuit breaker

Abstract: A three-phase common tank type gas circuit breaker has a grounded tank (1) filled with an insulating gas and accommodating three interrupter assemblies (4, 5, 6) for three phases of the electric power. Each assembly includes a parallel electrical connection of an interrupter having stationary (7) and movable contacts (8), a capacitor (12) and a closing resistor (13). The interrupters (4, 5, 6) for the three phases are disposed in spaced relationship circumferentially of the tank (1) and have axes extending axially of the tank (1). The closing resistor (13) for each phase is disposed on one side of the associated interrupter (4, 5, 6) adjacent an adjacent interrupter for a different phase, while the capacitor (12) for each phase is disposed on the inner or outer side of the associated interrupter (4, 5, 6), whereby the radial and axial dimensions of the grounded tank (1) can be reduced.

Description: The present invention relates to a three-phase common tank type gas circuit breaker according to the preamble of claim 1. Description of the Prior Art Power systems of high voltage and large capacity are becoming a matter of great concern in view of the recent increasing demand for electrical power. This has given a rise to a demand for increased capacities of circuit breakers used in substations to break greater powers of higher voltages. Circuit breakers also are required to have a reduced number of breaks as well as to cope with the increase in the power to be broken, in order to attain an improved braking performance. More specifically, dual break type circuit breakers capable of breaking 50 KA current, usable in 550 KV line for example, has been put in practical use. Nowadays, however, a demand exists for single break circuit breakers of the same class as above. This applies also to the case of gas-insulated circuit breakers. For instance, EP-A-0 355 338 describes a single break circuit breaker which is a so-called three phase common tank type gas circuit breaker in which interrupters for three phases are accommodated by a common hermetic tank so as to reduce the size of the whole gas-insulated circuit breaker. In this circuit breaker, in order to deal with an electric line of a large capacity of the order of 550 KV, a closing resistor for limiting closing switching overvoltage and a capacitor for limiting transient recovery voltage are disposed in parallel with the interrupter of each phase. In the prior art described, the circuit breaker has a grounded tank and three-phase assemblies for the three phases of the power accommodated in the grounded tank, each assembly having an interrupter, a closing resistor and a capacitor connected in parallel with the interrupter. More specifically, the closing resistors are disposed on the radially inner side of the interrupters and the capacitors are disposed in the central region of the grounded tank, the closing resistors and the capacitors being shielded by a cylindrical shield member. Single break function requires that one interrupter is associated with a capacitor which corresponds in capacitance to those used for conventional dual break type breakers. In addition, circuit breakers for use in such a large power line as of 550 KV class require closing resistors which are as long as 1 meter and which are connected in series. The arrangement of the closing resisters in the prior art circuit breaker, therefore, cannot provide a compact structure of the circuit breaker because the dimensions of the circuit breaker tend to be increased due to large axial dimensions of the closing resistors. SUMMARY OF THE INVENTION Accordingly, the object of the present invention is to provide a compact three-phase common tank circuit breaker for high voltage. This object is met by a three-phase common tank type gas circuit breaker according claim 1. Preferred embodiments are described in the subclaims. A three-phase common tank type circuit breaker according to the present invention comprises interrupters for the three phases disposed at a predetermined circumferential spacing within the grounded tank such that the axes of the interrupters extend substantially in parallel with the axis of the grounded tank, a closing resistor for each phase disposed on one side of the associated interrupter adjacent a neighboring interrupter of a different phase, a capacitor for each phase disposed in the grounded tank on the inner or outer side of the associated interrupter, and shield members provided for the stationary and movable sides of the interrupter for each phase. The closing resistors for the three phases are disposed at a circumferential interval and located in the vicinity of the associated interrupters in the grounded tank, while the capacitors are disposed on the radially inner or outer sides of the associated interrupters and in close proximity therewith. Therefore, the axial and radial dimensions of the grounded tank can be reduced to provide a compact gas circuit breaker. The advantages of the present invention will become more apparent from the following description with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a vertical sectional view of an embodiment of the gas circuit breaker in accordance with the present invention; Fig. 2 is a sectional view taken along the line II-II of Fig. 1; Fig. 3 is a sectional view taken along the line III-III of Fig. 2; Fig. 4 is a cross-sectional view of another embodiment of the gas circuit breaker in accordance with the present invention; and Fig. 5 is a sectional view taken along the line V-V of Fig. 4. DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. Referring to Figs. 1 to 3 which show an embodiment of the present invention, a grounded tank 1 has lead portions 1A and 1B which project radially outward from the wall of the tank 1 at an upper portion and a lower portion of the tank 1. These lead portions are hermetically closed by insulating spacers 2A and 2B. An operating equipment 3 for operating interrupters is provided in the lower part of the grounded tank 1. The grounded tank 1 is charged with an arc quenching gas and accommodates three interrupters 4, 5 and 6 for three phases of the electrical power arranged substantially at 120° interval, as will be seen from Fig. 2. In the illustrated embodiment, these interrupters are arranged such that their axes extend vertically. The interrupters 4, 5 and 6 are of so-called puffer type. Thus, each interrupter has a stationary contact 7 and a movable contact 8 opposing to the stationary contact 7. The stationary contactor 8 is connected to an upper lead conductor 9, while the movable contact 8 is connected to a lower lead conductor 10. The movable contacts 8 for the three phases are adapted to be moved into and out of contact with associated stationary contacts 7 by the operation of the operation equipment 3. Arcs generated by separation of the movable contacts 8 from the stationary contacts 7 are extinguished by blows of a high-pressure gas generated by gas compression means represented by puffer cylinders 11. Capacitor means 12 for limiting transient recovery voltage and closing resistors 13 for limiting closing switching overvoltage are disposed in each of the interrupters 4 to 6. The capacitor means 12 includes mounting members 12A, 12B which also act as connecting conductors and which are provided on the stationary contact 7 and the movable contact 8, respectively, an insulating bulkhead 12C provided between the mounting members 12A and 12B and having axial columnar cavities, and a plurality of capacitor elements 12D received in the cavities in the bulkhead. The insulating bulkhead 12C suppresses any influence of a hot gas generated at the time of breaking and improves the insulation between different phases. In order to enable an efficient use of the limited space in the grounded tank, the capacitor means 12 have arcuate cross-sections and are positioned at radially inner sides of the interrupters 4, 5 and 6. Each closing resistor has a moving resistor contactor 13A associated with the moving contactor 8, a stationary resistor contactor 13B associated with the stationary contact 7, and resistor elements 13C provided between the stationary resistor contactor 13B and the stationary contact 7. In order to minimize the dimension in the axial direction, the resistor is composed of stacks of resistor elements (13C) grouped into two groups which are arranged on both sides of each of the interrupters 4, 5 and 6 and which are supported and connected through mounting members 13D to 13F which also serve as connecting conductors, as will be seen from Figs. 2 and 3. Namely, as will be clearly understood from Fig. 2, the resistor elements (13C) of the resistor for each phase are arranged in the circumferential direction rather than in the radial direction of the grounded tank 1. This arrangement is effective to reduce the radial and axial dimensions of the grounded tank 1. Referring again to Fig. 2, each of the interrupters 4 to 6 is provided with an electric-field reducing shield member 14 which covers the stationary side of the interrupter, i.e., the stationary contact 7, the stationary resistor contactor 13B and the resistor elements 13C of the closing resistor, and a part of the capacitor 12. A shield member 15 also is provided on the movable side of each of the interrupters 4, 5 and 6 so as to partly cover the movable contact 8 and a part of the capacitor 12. Each of the shield members has greater radii of curvatures at their portions facing different phases and the ground than at other portions and, hence, exhibits an elliptic cross-section. The grounded tank 1 is provided with maintenance hand holes 16 formed in the portions thereof adjacent the interrupters 4 to 6. In the illustrated embodiment, since the resistor elements 13C of the closing resistor 13 are arranged in two groups which are disposed on both sides of each of the associated interrupter 4, 5 and 6 and extend in parallel with the axis of the interrupter, any increase in the radial and axial dimensions of the grounded tank due to installation of the resistor elements 13C can be suppressed. More specifically, the diameter of the grounded tank can be reduced to 70% of that of the known three-phase common tank type gas circuit breaker discussed in the description of the prior art. In addition, the insulated bulkhead of the capacitor 12 effectively prevents mixing of hot gases generated from different phases at the time of breaking, thus preventing reduction in the insulation between different phases. Furthermore, inspection and replacement of the component parts of the interrupters are facilitated by virtue of the provision of the hand holes 16. Figs. 4 and 5 show another embodiment of the present invention. In these Figures, the same reference numerals are used to denote the same parts or components as those in the embodiment shown in Figs. 1 to 3. This embodiment is suitable for use in the case where the closing resistor has a greater capacity. The resistor elements 13C are arranged in three parallel groups which are disposed on one side of the associated interrupters 4, 5 and 6 and which are supported by mounting members 13G to 13J which also serve as connecting conductors. It will be clear that this embodiment offers the same advantages as those provided by the embodiment described hereinabove. The described embodiments of the invention have reduced dimensions of the grounded tanks and, thus, can conveniently be used in a gas-insulated switch gear, making it possible to reduce the length of generating line, thus enabling the size and the cost of the switch gear to be reduced. According to the present invention, the dimension of the grounded tank can be reduced not only in the axial direction but also in the radial direction by virtue of the fact that the closing resistors of respective interrupters are disposed at the sides of the interrupters. It is therefore possible to provide a three-phase common tank type gas circuit breaker with minimized tank diameter.

Claims: A three-phase common tank type gas circuit breaker comprising a grounded tank (1) adapted to be filled with insulating gas, an interrupter (4, 5, 6) for each phase including a stationary contact (7) and a movable contact (8) and being disposed at a predetermined circumferential spacing within said grounded tank such that an axis of said interrupter extends substantially in parallel with an axis of said grounded tank, capacitor means (12) for each phase disposed on one of the inner and outer sides of the associated interrupter, closing resistor means (13) having resistor elements (13C) and stationary and movable resistor contacts (13A, 13B), and shield members (14, 15) provided for the stationary and movable parts of said interrupter for each phase, characterised in that said resistor elements (13C) of said closing resistor means (13) are disposed at least at one side of the associated interrupter (4, 5, 6), said side being adjacent to a neighbouring interrupter (4, 5, 6) of a different phase. The gas circuit breaker according to claim 1, wherein said shield members (14, 15) of each interrupter (4, 5, 6) have larger radii of curvatures at their portions facing other interrupters and the grounded tank (1) than at other portions. The gas circuit breaker according to claim 2, wherein said shield members (14, 15) have an elliptical cross-sectional shape. The gas circuit breaker according to any of claims 1 to 3, wherein said resistor elements (13C) of said closing resistor means (13) are disposed in parallel with at least one side of the interrupter (4, 5, 6). The gas circuit breaker according to any of claims 1 to 3, wherein said resistor elements (13C) of said closing resistor means (13) are disposed in parallel with both sides of the interrupter (4, 5, 6). The gas circuit breaker according to any of claims 1 to 5, wherein said capacitor means (12) has capacitor elements (12A, 12B) accommodated in cavities formed in an insulated bulk head (12C). The gas circuit breaker according to any of claims 1 to 6, wherein each interrupter (4, 5, 6) comprises a mounting member (13D, 13E, 13F), said mounting member being attached to the stationary contact (7) of said interrupter and being electrically connected to said resistor elements (13C) of said closing resistor means (13). The gas circuit breaker according to any of claims 1 to 7, wherein said ground tank (1) has maintenance hand holes (16) formed in the portion of the tank (1) being adjacent to said interrupters (4, 5, 6). The gas circuit breaker according to any of claims 1 to 8, wherein said interrupters (4, 5, 6) are arranged substantially in intervals of 120°.

Inventors: KISHI TUNEO, MINAKAWA TAKASHI, NISHIDA ISAO, YATSUZUKA HIROHIKO, KISHI, TUNEO, MINAKAWA, TAKASHI, NISHIDA, ISAO, YATSUZUKA, HIROHIKO
Applicants: HITACHI LTD, HITACHI, LTD.
Application year: 1991
Main classification: H01H33
IPC codes: H01H33