Power package for a power distribution system

Abstract: In a distributor, a plurality of switches are connected in series with one another on main distribution lines emerging from a receiver switching apparatus, thus forming a trunk. A branch line extends from a junction between each pair of adjoining switches and leads to each load via another switch and a transformer, wherein each pair of switches on the trunk is formed as a single branch unit, and the switch and transformer are united as a power package. In each power package, a supply bushing and a load bushing are placed on the top of a transformer, and shielded with closed housings. A switch is placed in the closed housing for the supply bushing, and a distribution board is placed in the closed housing for the transformer. This configuration enables the disconnection of any branch distribution lines from the main distribution lines and diminishes the installation space.

Description: TECHNICAL FIELD The present invention relates to a power package for use in a power distribution system at a building, factory, or the like. BACKGROUND ART Fig. 11 shows a conventional distribution system at a building. In Fig. 11, 1 denotes a building. 2 denotes a receiver switching apparatus installed in an electric room on the basement of the building 1. 3 denotes a circuit breaker. 4 denotes a high-tension bus. 5 denotes circuit breakers. 6 denotes transformers. 7 denotes molded-case circuit breakers associated with loads. 8 denotes cables to be connected to the loads. The receiver switching apparatus 2 places received power on the high-tension bus via the circuit breakers 3. Branch circuit breakers associated with loads in the building 1 are connected over the high-tension bus 4. Power is fed to the loads via the transformers 6 and molded-case circuit breakers 7. These equipments are usually installed in a main electric room on the basement. In a large-scale building, the equipments are installed in a sub-electric room, which receives power from the main electric room, on each floor. From the electric rooms, cables are laid radially toward loads. A prior art relating to loop distribution has been disclosed in Japanese Patent Laid-Open No.61-8645, which, however, poses a problem concerning the safety within a cable shaft. Besides, when an attempt is made to modify the rating of a branch transformer, a power cut becomes necessary. Thus, the handling efficiency is poor. A conventional distribution system has the aforesaid configuration that cables are laid radially from an electric room to loads. A lot of cables are therefore required, many man-hours are needed for cable connection, and eventually the construction costs high. Furthermore, it takes much time to complete the construction, and the system takes up a lot of space. A conventional loop distribution facility also has problems concerning safety and handling efficiency. EP 0 049 642 A discloses an attempt to reduce the size of a gas-insulated electrical apparatus for use in a power distribution system by arranging a power transformer and switchgear within a common sealed housing. The transformer and switchgear are mounted side by side. In a variant the common housing may be divided by a vertical partition, with the transformer on one side and the switchgear on the other, connected via a bushing mounted on the partition wall. While this improves the compactness of the apparatus, the resulting package still occupies a considerable floor area. The present invention attempts to solve the above problems. An object of the present invention is to provide a power package that can easily be put into operation with a compact configuration. Another object of the present invention is to provide a high-safety power package for a distribution system. Yet another object of the present invention is to provide a power package permitting uninterrupted power feed with high reliability. Still another object of the present invention is to provide a power package permitting easy maintenance. DISCLOSURE OF THE INVENTION For a compact power package, a supply bushing and a load bushing are arranged on the top of a transformer, and then shielded with closed housings. A switch is installed in the closed housing for the supply bushing, and a distribution board is placed on the closed housing for the transformer. In order to realize the supply and load terminals in a power package with independent closed structures, a supply bushing and a load bushing are arranged on the top of a transformer, and two independent closed housings are mounted on the top of the transformer. One of the closed housings serves as a switch room for storing a switch directly coupled with a conductor penetrating through the supply bushing, while the other closed housing serves as a bus room in which a bus connected to the conductor penetrating through the load bushing is laid. In order to design a transformer in a power package compactly, a gas-insulated transformer is adopted. In order to provide long-term reliability for a high-tension circuit, the switch room in the above structure is realized with a gas-insulated container filled with insulation gas. For easy mounting or dismounting of a switch, at least a junction between a switch and a transformer is made up of a contact and a contact conductor that is freely coupled with or decoupled from the contact. In a distribution system relating to the present invention, load switches are connected to multiple branch points on first and second main distribution lines emerging from an receiver switching apparatus. The load terminals of each pair of the load switches connected on the first and second main distribution lines are coupled with each other as a common from which a branch line extends to each of distributed loads via a switch and a transformer. Switches are combined in twos to form independent branch units. The branch units are connected in series with one another on main distribution lines emerging from an receiver switching apparatus, thus forming a trunk. Power packages, in each of which another switch and a transformer are connected in series with each other, are connected to the branch units, and extending branch lines to loads. In the present invention, power is fed to the vicinities of distributed loads over main distribution lines. Power is then supplied to the loads over branch distribution lines branching out from the main distribution lines. Switches are installed across each branch point on the main distribution lines, which control the orientation of power flowing into the corresponding branch distribution line. A switch is also inserted to each branch distribution line, so that the the branch distribution line can be disconnected from either of the main distribution lines. Each pair of switches on the main distribution lines, which are coupled with each of branch distribution lines, is formed as a single branch unit. Branch units are installed in a cable shaft, thus diminishing an installation space. In each branch unit, a junction with a main distribution line or a switch is shielded with a housing. If fire should break out at the junction or switch, the outside of the branch unit can be held unsusceptible to the influence of the fire. Switches in each branch unit are installed with the junctions thereof facing up. The cable of a main distribution line or branch distribution line is therefore taken in from above the branch unit. A switch and a transformer on each branch distribution line are united as a power package. A simple configuration ensues. A supply bushing and load bushing are arranged on the top of a transformer, and shielded with closed housings. The supply bushing is coupled with a switch. This structure helps reduce the installation area of a distributor. In each power package, a switch room and a bus room are formed as independent closed structures. A failure of either of the structures will not influence the other one. During maintenance inspection, the structures will not be disturbed by a high-tension charger. Thus, maintenance inspection can be achieved with safety. A gas-insulated transformer is adopted as a transformer in each power package, which results in a compactly-designed distributor. A switch room in each power package is filled with insulation gas, thus shutting out the environmental factors deteriorating the insulation performance of a high-tension circuit. This provides long-term reliability. The junction with a switch in each power package consists of a contact and a contact conductor. This obviates bolting, and simplifies and speeds up mounting or dismounting of a high-tension switch. BRIEF DESCRIPTION OF DRAWINGS Fig. 1 is a first distribution system diagram showing power packages according to the present invention; Fig. 2 is an oblique view showing the installation of a branch unit and a power package in the first distribution system; Fig. 3 shows an A-A cross section of Fig. 2; Fig. 4 shows a B-B cross section of Fig. 3; Fig. 5 shows a C-C partial cross section of Fig. 2, showing a first embodiment of a power package according to the present invention; Fig. 6 is a left side view of Fig. 5; Fig. 7 is a partial cross-sectional view showing a second embodiment of a power package according to the present invention; Fig. 8 is a partial cross-sectional view showing a third embodiment of a power package according to the present invention; Fig. 9 is a second distribution system diagram showing power packages according to the present invention; Fig. 10 is an oblique view showing the installation of a branch unit and a power package in the second distribution system; and Fig. 11 is a distribution system diagram of a prior art. BEST MODE FOR CARRYING OUT THE INVENTION Fig. 1 shows a distribution system in a building employing power packages according to the present invention. In Fig. 1, 1 denotes a building. 1a denotes a cable shaft extending vertically within the building 1. 2 denotes an receiver switching apparatus installed in an electric room on the basement of the building 1. 6 denotes transformers. 7 denotes molded-case circuit breakers associated to loads. 8 denotes cables leading to the loads. 9 and 10 denote main distribution lines which are emerging from the receiver switching apparatus 2 and laid within the cable shaft 1a. 11 and 12 denote main distribution line switches that are connected in series with one another on the main distribution lines 9 and 10 and installed across respective branch points. 11 denotes first switches, while 12 denotes second switches. 13 denotes branch units containing the main distribution line switches 11 and 12. 14 denotes branch distribution lines extending from the branch units 13. 15 denotes load switches connected on the branch distribution lines 14. 16 denotes power packages according to the present invention, each containing a transformer 6 and one of the load switches 15. In Fig. 1, the molded-case circuit breakers 7 are included in the power packages 16. The molded-case circuit breakers 7 may be installed outside the power packages 16. Fig. 2 is a schematic diagram showing the appearances of a branch unit 13 and a power package 16, and the cable connection. In Fig. 2, 1b denotes a partitioning member for partitioning the inside of the cable shaft up and down. 1c denotes a through hole bored on the partitioning member 1b. 1d denotes a through hole bored on the side wall of the cable shaft 1a. 13a and 13b are junctions between main distribution switches 11 and 12, and main distribution lines. 13c denotes a junction with a branch distribution line 14. Fig. 3 is a cross-sectional diagram viewing the branch unit 13 in Fig. 2 in the A-A direction. Fig. 4 is a cross-sectional diagram viewing Fig. 3 in the B-B direction. 11 and 12 denote main distribution switches placed in parallel with each other beneath the branch unit 13 with the junctions 13a and 13b facing up. In Fig. 3, three phase switching devices 11a or 12a are installed in the depth direction of the main distribution line switch 11 or 12. 17 denotes a branch, which has the same appearance as those of the main distribution switches 11 and 12. The branch 17 has a junction 13c at one end thereof. The junction 13c is coupled with a common junction of the main distribution switches 11 and 12 within the branch 17. 12a denotes an operating mechanism for the main distribution line switch 12. 13d denotes a housing for the branch unit, shielding the junctions 13a to 13c. 13e denotes a front door of a branch unit, in the upper part of which a display unit 13f is mounted to enable observation from outside. 13g denotes cable supports for supporting main distribution lines 9 and a branch distribution line 14. Fig. 5 is a partial cross-sectional diagram viewing the power package 16 in Fig. 2 in the C-C direction. Fig. 6 shows the left side of Fig. 5. In this embodiment, a gas-insulated transformer is adopted as a transformer 6. 18 and 19 denote bushings placed on the top of the transformer 6. 18 denotes a supply bushing, while 19 denotes a load bushing. 20 denotes a distribution board that accommodates a molded-case circuit breaker 7 connected to a load and adjoins the side of the transformer 6. 21 denotes a bus linking a terminal 19a of the bushing 19 with the distribution board 20. 22a denotes a closed cover for shielding the bushing 19 on the top of the transformer 6 and the top and side of the bus. 15 denotes a switch. Switching devices 15b operated by a means, which is not shown, are located in a sealed container 15a and fixed to the sealed container 15a via a bushing 15c. The switching sections 15b number three (for three phases) and line up in the depth direction in Fig. 5. 15d denotes a contact supported by a conductor 15e. The contact 15d is coupled with an end of a bushing terminal 18a (contact conductor) so as to be freely decoupled therefrom. The conductor 15e is supported via an insulator 15h by a supporting member 15g that is fixed to the sealed container 15a. Ones of the ends of the switching devices 15b are connected to one of the ends of the conductor 15e via flexible conductors 15k. The sealed container 15a is filled with insulation gas such as SF 6 gas. 6a denotes a coupling flange that surrounds annularly the side circumference of the bushing 18a and is attached to the top of the transformer 6 airtightly. The coupling flange 6a is coupled with the sealed container 15a having an opening on the bottom. In this embodiment, the closed cover 22a and sealed container 15a are separate members. The final assembly or the combination of the closed cover 22a and sealed container 15a constitutes a closed housing 22. When the switch 15 is to be dismounted from the transformer 6, the coupling flange 6a is disconnected from the sealed container 15a and the switch 15 is lifted. The contact 15d then departs from the bushing terminal 18a. This completes the dismounting of the switch 15. In a distribution system having the aforesaid configuration, the main distribution lines 9 and 10 emerging from the receiver switching apparatus 2 ascend within the cable shaft 1a, and alternately couple the main distribution line switches 11 and 12, which are located in the branch units 13, in series with one another. The main distribution lines 9 and 10 are linked with each other on the uppermost floor, thus forming a loop. In actual power transmission, a distribution system is operated in such a state that any one of the switches 11 and 12 in the loop is broken to create an open loop. This is intended to simplify the locating of a point of any accident if happens. For instance, when the distribution system is operated with the switch 12 at a point D on the uppermost floor broken, power supply to loads on the uppermost floor is achieved over the main distribution line 9 via the branch distribution lines 14, switches 15, transformers 6, molded-case circuit breakers 7, and cables 8. To stop the power supply to a load, a switch 15 associated with the load must be broken. When the power supply to an entire power package 16 must be stopped due to a failure of any transformer 6 or a change in the installed capacity of a load, the main distribution switches 11 and 12 directly connected to the power package 6 are broken. Thus, while power is being fed to the loads on the other floors, the power supply to the floor concerned alone can be stopped. If any branch unit 13 fails, the switches 11 and 12 for the branch unit 13 connected across the branch unit 13 are broken to stop the power supply to the branch unit 13. Inspection, repair, or replacement can then be carried out. In this configuration, in each branch unit, switches 11 and 12 and junctions 13a, 13b, and 13c, which are prone to a fire, are shielded with a housing. An accident is therefore unlikely to expand, and high safety is ensured. The main distribution line switches 11 and 12 are placed in the lower part of each branch unit 13 with their junctions facing up. so that main distribution lines 9 and 10 or a branch distribution line 14 can be pulled in from above the branch unit 13 and then connected. This structure allows an operator to carry out cable connection at the height of his/her chest. The connection work is therefore easy to do. Moreover, the installation area can be diminished. As a result, branch units 13 can be installed in a cable shaft. This means that a loop configuration can be realized within a limited installation area. In this embodiment of a power package 16, a closed housing 22 is placed on a transformer 6. A switch 15 is installed in the closed housing 22. A distribution board is placed adjacently to the side of the transformer 6. Consequently, the installation area for a power package 16 diminishes. When only a small number of molded-case circuit breakers 7 is connected to loads, the upper part of a load bushing 19 on the top of the transformer 6 may be used as a distribution board. This further diminishes the installation area for the power package 16. When a gas-insulated transformer is adopted as the transformer 6, with the capacity unchanged, the transformer 6 can be constructed more compactly than a conventional oil-filled transformer or a molded transformer. Furthermore, since the number of combustible materials is limited, safety improves. In this embodiment, a sealed container 15a for a switch 15 is filled with SF 6 gas. The insulation performance therefore improves. Furthermore, the switch becomes unsusceptible to external environmental factors such as pollution, and offers long-term reliability. A contact 15d is used for the junction of the switch 15 with a transformer 6, which obviates bolting or unbolting for connection. This results in quick and simple mounting or dismounting of the switch 15. Fig. 7 partly shows a side cross section of another embodiment of a power package 16. A closed housing 22 for shielding supply and load bushings 18 and 19 is mounted on the top of a transformer 6. In this embodiment, a switch 15 has moving wheels 15n. The switch 15 can therefore be pulled out sideways in Fig. 7. The tips of the terminals of the switch 15 are provided with contacts 15d, and thus can be coupled with or decoupled from bushing terminals 18a and 15m. The closed housing 22 shields the switch 15 and a bus 21 as a whole. The supply and load bushings 18 and 19 are separated by a grounded metallic partition 22b. In a power package having the aforesaid structure, the inside of the closed housing 22 is divided into a room for the switch 15 and a room for the bus 21 by the grounded metallic partition 22b. A short circuit or other failure in the room for the bus 21 will not affect the supply terminal. During maintenance inspection of the load terminal, since the load terminal is isolated by the grounded metallic partition 22b, there is no fear that the load terminal is disturbed by the supply terminal serving as a charger. Thus, safety is ensured. With the movement of the switch 15 owing to the wheels 15n, the contacts 15d at the tips of the terminals are coupled with or decoupled from the bushing terminals 15m and 18a respectively. Mounting or dismounting of the switch 15 is therefore very easy to do. This means that the time of a power stoppage for replacement is very short. In Fig. 7, the closed housing 22 is shared by the supply terminal and the load terminal, and partitioned by installing the ground metallic partition 22b. The closed housing 22 may be made up of respective housings for the supply and load terminals, which also provides the same advantages as that in the aforesaid embodiment. Fig. 8 is a cross-sectional diagram showing part of yet another embodiment of a power package 16. In this embodiment, a bushing 15 is projecting laterally and coupled with a branch distribution line 14. This arrangement lessens the required height of the power package 16. Figs. 9 and 10 show a second distribution system, and a branch unit and a power package. In Fig. 9. a main distribution line 9 ascends within a cable shaft 1a and leads to switches 11 in branch units 13 via branch lines 9a branching out from T points on the main distribution line 9. A main distribution line 10 ascends within the cable shaft 1a and leads to switches 12 in the branch units 13 via branch lines 10a branching out from T points on the main distribution line 10. Equipments connected to the load terminal beyond each of the branch units 13 are identical to those shown in Figs. 1 and 2. In the foregoing configuration, the branch units 13 are connected on both the main distribution lines 9 and 10. In the operational state, either the switches 11 or 12 are broken, and power is fed through the other switches. If either of the main distribution lines 9 and 10 fails, the other main distribution line, which has not failed, is activated so as-to feed power uninterruptedly. If any of power packages 16 fails, both the switches 11 and 12 in the power package concerned are broken. This enables safe inspection or replacement without causing power stoppages in the other power packages. In the first embodiment of a power package, a closed housing different from the one forming a bus room is provided as a switch room. The closed housing forming the switch room is realized with a gas-insulated container. In the second embodiment, the inside of a closed housing is divided into a switch room and a bus room using a grounded metallic partition. In an alternative embodiment, a closed housing that is of the same kind as and independent of the one forming a bus room may be used as a switch room. As described above, in a distribution system incorporating the power packages according to the present invention, multiple switches are connected in series with one another on main distribution lines emerging from a receiver switching apparatus, thus forming a trunk. A branch line is extending from a junction between each pair of adjoining switches into each of distributed loads via a switch and a transformer. The number of cables decreases and the man-hours required for cable connection lessens. This results in a distributor capable of being put into operation easily. Each pair of switches is formed as a single branch unit. The branch units are connected in series with one another on main distribution lines emerging from a receiver switching apparatus, thus forming a trunk. Power packages, in each of which another switch and a transformer are connected in series with each other, are connected to the branch units, and leading brand lines to loads. This results in a distributor capable of being put into operation easily. Branch units are installed in a cable shaft, and concatenated over main distribution lines. This results in a distributor capable of being installed in a limited space. Each branch unit consists of first and second main distribution switches and a housing for shielding the switches. This results in compact distributor. Each branch unit includes at least first and second main distribution switches and a housing for shielding the switches. The switches are located in the lower part of the housing with the junctions facing up. A branch line and main distribution lines are taken in from above the housing. This results in a distributor that requires a limited installation area and simplifies installation work. A supply bushing and a load bushing are arranged on the top of a transformer in each power package, and shielded with closed housings. A switch is installed in the closed housing for the supply bushing, and a distribution board is placed by the side of the transformer. This results in a compact power package. In order to realize the supply terminal and load terminal of each power package with independent closed structures, a supply bushing and a load bushing are arranged on the top of a transformer. Moreover, two independent closed housings are mounted on the top of the transformer. One of the closed housings serves as a switch room for storing a switch directly coupled with a conductor penetrating through the supply bushing. The other closed housing serves as a bus room in which a bus connected to a conductor penetrating through the load bushing is laid. This results in a safe power package. A gas-insulated transformer is adopted as a transformer in each power package, which contributes to materialization of a compact power package. A gas-insulated container filled with insulation gas is adopted as each switch room, which provides a power package capable of providing long-term reliability for each switch room. Each junction between a switch and a transformer is composed of a contact and a contact conductor that can be freely coupled with or decoupled from the contact. This results in a power package permitting easy maintenance.

Claims: Power package, wherein: a supply bushing (18) and a load bushing (19) are placed on the top of a transformer (6); said supply bushing (18) and said load bushing (19) are shielded with closed housings; a switch (15) is placed in the closed housing for said supply bushing (18); and a distribution board (20) is located by the side of said transformer (6). Power package, wherein: a supply bushing (18) and a load bushing (19) are placed on the top of a transformer (6); two independent closed housings are mounted on the top of said transformer (6); one of the housings serves as a switch room for storing a switch (15) directly coupled with a conductor (18a) which penetrates through said supply bushing (18); the other housing serves as a bus room in which a bus (21) leading to a conductor (19a) which penetrates through said load bushing (19) is laid; and a distribution board (20) is placed by the side of said transformer (6). Power package according to claim 1 or 2, characterized in that said transformer (6) is a gas-insulated transformer. Power package according to any of claims 1 to 3, characterized in that said switch room is filled with insulation gas. Power package according to any of claims 1 to 4, characterized in that at least each junction between a switch (15) and a transformer (6) is composed of a contact (15d) and a contact conductor (15e) that can be freely coupled with or decoupled from said contact (15d).

Inventors: HOSOYA RYOUZOU, NAKAHATA MINORU, ORITO NOBUYUKI, SAKAI MICHIO, HOSOYA, RYOUZOU, NAKAHATA, MINORU, ORITO, NOBUYUKI, SAKAI, MICHIO, Hosoya, Ryouzou, c/o Mitsubishi Denki K.K., Nakahata, Minoru, c/o Mitsubishi Denki K.K., Orito, Nobuyuki, c/o Mitsubishi Denki K.K., Sakai, Michio, c/o Mitsubishi Denki K.K.
Applicants: MITSUBISHI ELECTRIC CORP, MITSUBISHI DENKI KABUSHIKI KAISHA
Application year: 1992
Main classification: H02B7
IPC codes: H02B1, H02B7