GAS INSULATED SWITCHGEAR

Abstract: A gas insulated switchgear comprises a pair of main buses (1, 2) disposed substantially in parallel with a distance therebetween, groups of circuit breakers (3, 4, 5) installed between the main buses and each group including a serial connection of three circuit breakers connected in series by a connecting bus (20, 23) for each phase, the serial connection having ends electrically connected to the main buses and insulated leading-out means (12, 13) led out from the connecting buses between the circuit breakers by way of branching buses (21, 24). The three circuit breakers (3, 4, 5) are juxtaposed so that respective axes intersect orthogonally the parallel axes of the main buses (1, 2). The connecting buses (20, 23) are disposed above the main buses (1, 2) and serve to connect serially the adjacent ones of the circuit breakers The branching buses are connected to the connect­ ing buses, respectively. The site area for installation of the switchgear can be significantly reduced and implementation of the switchgear is facilitated.

Description: GAS INSULATED SWITCHGEAR The present invention generally relates to a gas insulated switch equipment, and more particularly to a gas insulated switchgear of the one and halfbreaker system. As one of arrangements of the substation for an extra-high voltage power system, there is known a so-called one-and-half breaker system in which a gas insulated switchgear basically composed of three gas insulated circuit breakers electrically connected in series to one another is employed. In the gas insulated switchgear, three circuit breakers each being equipped with disconnectors (i.e. d.isconnecting switches) at both ends, respectively, are arrayed linearly, wherein both ends of the linear array of the circuit breakers are connected to gas insulated main buses. Bushings are connected between evey adjacent two of the circuit breakers and serve to connect the gas insulated switchgear to a power transmission line system. Two sets of steel tower pairs are provided for suspending or supporting the transmission line, wherein the into-tower distance between paired steel towers in each set is determined so that the air insulation distance can be assured in vhe state in which three phase transmission lines are horizontally suspended. Since the two sets of towers are facing to each other with a predetermined distance therebetween corresponding to the axial length of the gas insulated switchgear, the structure in which the serial connections of three circuit breakers are disposed in the linear array as described above is of relatively large size. Further, in order to assure the air insulation distance between the bushings among the juxtaposed three phase paths, the axial length of the main buses as well as the intertower distance are generally large. In other words, the hitherto known gas insulated switchgear of the one-and-half breaker system has required a large site area for installation as well as a large scale suspension tower structure. To deal with the above problem, it has been proposed that three groups, each including three circuit breakers of single-phase type for respective phases, are disposed in juxtaposition or three circuit breakers of three-phase common enclosure type are installed in parallel to the main buses. For example, reference may be made to Japanese Patent Application Laid-Open No. 59002/1984. More specifically, the first mentioned proposal resides in that three groups each including three circuit breakers are disposed in juxtaposition to one another between two main buses, wherein the circuit breakers of two selected groups are connected in series by a connecting bus of three-phase common enclosure type to which respective ends of branching buses of respective phases are connected, while the other ends of the branching buses are connected to the bushings. The circuit breakers of different two groups are connected in a similar manner by means of other connecting buses and the branching buses. With this arrangement, main buses are disposed above the axes of the grouped circuit breakers while the connecting buses are disposed below the axes. Consequently, the individual branching buses are led out from the connecting buses at positions located between the circuit breakers, respectively. As a result, dimension of each branching bus is increased for assuring the insulation distance for the bushing of each phase, involving complicated structure. Besides, distance between the adjacent groups of the circuit breakers is necessarily increased, which means that the site area for installation is increased, giving rise to a problem. In the case of the second mentioned proposal according to which three circuit breakers are disposed in parallel with each main bus in the one-and-half breaker system, the circuit breakers of vertical types are employed and arrayed linearly in the isolated phase arrangement. This construction also suffers from shortcomings in that the structure of the branching buses each of relatively great length is complicated, requiring thus a large site area for installation to disadvantage. Under the circumstances, there exists a demand for solving the problems mentioned above in conjunction with the gas insulated switchgear of the one-and-half breaker system. An object of the present invention is to provide a gas insulated switchgear of the one-and-half breaker system which allows the site area required for installation to be reduced significantly. Another object of the present invention is to provide a gas insulated switchgear of the one-and-half breaker system which can be implemented in a much facilitated manner. In view of the above objects, it is proposed according to an aspect of the invention that in realizing the gas insulated switchgear of the one-and-half breaker system, three circuit breakers are disposed in juxtaposition so that the axes of main buses can be disposed in parallel, wherein connecting buses are disposed above the main buses, respectively, the adjacent ones of the circuit breakers being connected in series by the respective connecting buses. The present invention will be apparent from the following detailed description taken in conjunction with the accompanying drawings, in which: Fig. 1 is a plan view showing a gas insulated switchgear according to a first embodiment of the present invention; Fig. 2 is an elevational view of the gas insulated switchgear as viewed from the righthand side n Fig. 1; Fig. 3 is a front view of Fig. 1 in which branching buses and bushings are omitted from illustration; Fig. 4 is a plan view showing a gas insulated switchgear according to a further embodiment of the invention; and Fig. 5 is a side elevational view of the switchgear structure of Fig. 4 as viewed from the right-side thereof. Now, an exemplary embodiment of the gasinsulated switchgear will be described by referring to Figs. 1 to 3. In the case of this embodiment, there are used gas insulated circuit breakers of isolated phase horizontal construction type. A pair of main buses 1 and 2 are installed in parallel with each other with a predetermined distance therebetween. Disposed sequentially in juxtaposition between these main buses 1 and 2 are three groups of circuit breakers denoted collectively by reference numerals 3, 4 and 5, each group including three circuit breakers for three phases, respectively, and disposed in order of phase. A connecting bus 20 is installed between the two groups of the circuit breakers 4 and 5 above the corresponding main bus 1, while a connecting bus 23 is installed between the two groups of the circuit breakers 3 and 4 above the corresponding main bus 2. As will be described hereinafter, branching buses 21 and 24 provided for three phases, respectively, are connected to the connecting buses 20 and 23, respectively, at positions opposite to each other. Respective ends of the juxtaposed circuit breakers of the group 4 are connected 1 to the corresponding ends of the circuit breakers of the group 5 through the respective disconnectors and other elements as required and the connecting bus 20 overlying the main bus 1 on the phase-by-phase basis, while the other ends of the circuit breakers of the group 5 are connected to the main bus 2 through respective disconnectors and other elements as required. The other ends of the circuit breakers of the group 4 are connected to the corresponding ends of the circuit breakers of the group 3 through the respective disconnectors and other elements and through the connecting bus 23 located above the main bus 2, while the other ends of the circuit breakers of the groups 3 are connected to the main bus 1 through the respective disconnectors and other elements. In this manner, a one-and-half breaker system is realized which includes for each phase the path extending from the main bus 1 through the circuit breakers of the group 3, the connecting bus 23 for connecting the branching bus 24, the circuit breakers of the group 4, the connecting bus 20 for connecting the branching bus 21 and the circuit breakers of the group 5 leading to the main bus 2. In the case of the illustrative embodiment, the branching buses 21 for individual phases have one ends connected to the connecting bus 20 at the axial positions thereof which are intersected by the extended axes of the circuit breakers of the group 4 of the corresponding phases, respectively, while the other end portions of the branching buses 21 are led out horizontally, being fanned out to assure inter-phase insulation distance, to be connected to respective bushings 13 each supported on a framework 13A and constituting an insulated leading-out means. Similarly, the branching buses 24 of the respective phases have one ends connected to the connecting bus 23 at the axial positions thereof which are intersected by the extended axes of the circuit breakers of the group 4 of the corresponding phases, respectively, while the other ends of the branching buses 24 are connected to respective bushings 13 supported on a framework 12A and constituting an insulated leading-out means. In the illustrated embodiment, each of the main buses 1 and 2 and the connecting buses 20 and 23 is constituted by a three-phase common enclosure type bus filled with an insulation gas. The axes of these buses 1, 2, 20, and 23 extend substantially perpendicularly to the axes of the circuit breakers of the groups 3, 4 and 5, wherein the main buses 1 and 2 are disposed below the circuit breaker groups, while the connecting buses 20 and 23 are installed above the circuit breakers. Further, it will be noted that the main bus 1 and the connecting bus 20 are disposed in parallel with the main bus 2 and the connecting bus 22 with the circuit breaker groups 3, 4 and 5 being interposed therebetween. With the illustrated arrangement in which the branching buses 21 and 24 are disposed on the extended axes of the circuit breakers belonging to the group 4, the distance between any adjacent groups of the juxtaposed circuit breakers can be descreased, as the result of which the site area for installation can be reduced about a half when compared with the case of the hitherto known switchgear. Further, because the connecting bus 20, the branching buses 21 and the bushings 13 on one hand and the connecting bus 23, the branching buses 24 and the bushings 12 on the other hand are disposed symmetrically relative to the circuit beaker group 4, the connecting buses, branching buses and bushings can be made same, to facilitate the implementa-:ion. The embodiment described above may also be applied to the system wherein the main buses land 2 and the connecting buses 20 and 23 are each made of three single-phase buses insulated from each other. In a varsion of this embodiment, the positions of the main bus 1 and 2 and the connecting buses 20 and 23 can be reversed. Although not illustrated, the suspension steel tower system may be of an integral structure in which a pair of steel legs are disposed in opposition to each other between the main buses 1 and 2 with a predetermined distance therebetween. The steel legs in turn are connected to each other by means of a beam member which in turn have suspension insulators for suspending aerial lines of individual phases mounted at both ends, respectively, wherein the aerial lines of the individual phases are connected to the corresponding bushings 12 and 13, respectively, which serve as the insulated leading-out means. Figs. 4 and 5 shows another embodiment of the present invention. In the case of this embodiment, each of the buses 1, 2, 20 and 23 is of a three-phase common enclosure type the same as that of Figs. 1, 2 and 3, while the circuit breaker as employed is of a known vertical type. In Figs. 3 and 4, like reference symbols are used to denote like components shown in Figs. 1 and 2. As will be seen in Fig. 5, the circuit breakers of the group 5 are enclosed within an upstanding tank having a vertical axis, wherein both terminals are led out in opposite horizontal directions, respectively. With this structure, same effects as those of the first embodiment can be attanined. Additionally, the distances between the main buses 1 and 2 and between the connecting buses 20 and 23 can be reduced when compared with the first embodiment, whereby a gas insulated switchgear of a more compact structure can be realized. The gas insulated switchgears according to the inventions are very suited for indoor service or application because of significantly reduced site area required for installation. As will now be appreciated, the gas insulated switchgear of the structure taught by the present invention allows the site area for the installation to be considerably reduced by virture of the appropriate relative disposition of the main buses, the connecting buses three circuit breakers for each phase. Further, due to symmetrical disposition of the main buses, the connecting buses and also the branching buses on both sides of the circuit breakers, construction or realization of the switchgear can be extremely facilitated, to another advantage.

Claims: CLAIMS 1. A gas insulated switchgear, comprising a pair of main buses (1, 2) extending substantially in parallel with a distance therebetween, three groups of circuit breakers (3, 4, 5) installed between said main buses and each group including a serial connection of three circuit breakers connected in series by connecting buses (20, 23) for each phase, said serial connection having ends electrically connected to said main buses, and insulated leading-out means (13) led out from the connecting buses between said circuit breakers by way of branching buses (21, 24), wherein said three circuit breakers (3, 4, 5) are juxtaposed so that respective axes intersect orthogonally the parallel axes of said main buses (1, 2), said connecting buses (20, 23) being disposed above said main buses (1, 2) and serving to connect serially the adjacent ones of said circuit breakers, said branching buses being connected to said connecting buses, respectively. 2. A gas insulated switchgear according to claim 1, wherein each of said main buses (1, 2) and connecting buses (20, 23) is of a three-phase common enclosure type. 3. A gas insulated switchgear according to claim 1, wherein each of said main buses (1, 2) is disposed below the center axes of the circuit breakers, while each of said connecting buses (20, 23) is disposed above the center axes of the circuit breakers. 4. A gas insulated switchgear according to claim 1, wherein each of said insulated leading-out means (12, 13) is mounted on an end of each branching bus led out horizontally from the center axis of each of said connecting buses (20, 23). 5. A gas insulated switchgear according to claim 1, wherein said main bus and said connecting bus are each of a three-phase common enclosure type, said connecting buses (20, 23) being disposed above said main buses (1, 2), said branching buses being horizontally led out by disposing symmetrically said connecting buses. 6. A gas insulated switchgear according to claim 1, wherein said groups of the circuit breakers are juxtaposed with a substantially same distance therebetween, said insulated leading-out means (12, 13) being disposed at a position of the connecting bus which is intersected by an extension of the center axis of the center circuit breakers.

Inventors: SAKAGUCHI, MINORU, SUZUYAMA, HIROSHI, TSUBAKI, TORU
Applicants: HITACHI, LTD.
Application year: 1986
Main classification: H02B13
IPC codes: H02B13, H02B5