A SYSTEM FOR ASSEMBLY AND MAINTENANCE OF CONNECTION MODULES IN HIGH-VOLTAGE SWITCHGEAR, A METHOD THEREFOR AND A SYSTEM COMPONENT

Abstract: The invention relates to a system and a method for assembly and maintenance of connection modules (3) in high-voltage switchgear (1). According to the invention assembly and maintenance are performed in a service bay (6) in the vicinity of the switchgear. Modules (3a) to be assembled, replaced or repaired are transported between the service bay (6) and its site (2a) in the switchgear area by a service vehicle (4). The vehicle (4), connection modules (3) and the positions for their base plates (2) are thus so adapted to each other that the service vehicle (4) can move about in the switchgear area while the switchgear is in operation. A special aspect of the invention is the custom-design of the service vehicle (4) specifically for its purpose.

Description: A SYSTEM FOR ASSEMBLY AND MAINTENANCE OF CONNECTION MODULES IN HIGH-VOLTAGE SWITCHGEAR, A METHOD THEREFOR AND A SYSTEM COMPONENT The present invention relates in a first aspect to a system for assembly and maintenance of connection modules in high-voltage switchgear, of the type described in the preamble to claim 1. From a second aspect the invention relates to a method for assembly and maintenance of such connection modules, of the type described in the preamble to claim 9. From a third aspect the invention relates to a central component in such a system, namely a service vehicle of the type described in the preamble to claim 15. Such switchgear generally includes a large quantity of electrical apparatus, in the following termed connection modules, which are arranged in a number of lines, normally three, which lines are oriented in the same direction as the overhead power transmission lines entering and leaving the switchgear. Each connection module is normally supported individually on a stand, i.e. each breaker, each disconnector, each earthing device, each surge diverter and each current meter has its own stand. The large number of components required in an air-insulated high- voltage switchgear station, and the demand for safe electrical distance between each unit mean that conventional switchgear occupies a considerable ground area. The extension in the direction of the overhead power lines of a switchgear for a voltage level of 245-500 kV, defining the length of the switchgear station, is approximately 100-150 meter. A 420 kV switchgear station would be typically about 120 m. Alternatively a plurality of electrical components may be combined in an apparatus part arranged on a common stand. Such connection modules can reduce the area occupied by the switchgear. A switchgear of such a type is described in Swedish patent application No. 96 02336-1 and various examples are described therein of how connection modules can be designed, where a common stand carries several com- ponents. The stands are placed at erection sites with base plates to anchor the stands. When connection modules for a switchgear are to be assembled in conventional manner the apparatus parts are transported to the respective erection sites, after which the parts are assembled on site by means of a mobile crane, for instance. Only when the apparatus parts are in place and have been assembled can the control cabling be installed and connected, usually directly to terminal blocks in the control devices. Maintenance work such as inspection of contacts or repairs according to conventional technology is also performed on the erection site using mobile cranes or the like. Parts of the switchgear in the vicinity must be taken out of operation and rendered dead throughout the time needed for the work. Such shut-downs can entail considerable costs and it would therefore be desirable to be able to reduce or eliminate shut-downs caused by such maintenance work. In the light of this, the object of the present invention is to provide a system for assembly and maintenance of connection modules in high-voltage switchgear in which the problems of forced shut-downs associated with conventional technology in the area are solved. According to the invention this is achieved by a system of the type described in the preamble to claim 1 which has been given the special features defined in the characteri- zing part of the claim, by a method of the type described in the preamble to claim 9 which includes the special mea- sures defined in the characterizing part of this claim, and by a component included in the system, i.e. a service vehicle as described in the preamble to claim 15 which comprises the special features defined in the characteri- zing part of this claim. The system and method are thus based on all that work in connection with assembly and service being performed at a place other than within the switchgear area, and that the assembled or repaired connection module is transported out to its erection site. This means that such work is eliminated on site and no shut-down in operation need occur. Transport of the connection modules could in fact be per- formed using a conventional fork lift truck. However, the transport places rather special demands on the transport vehicle when it is to drive a connection module out to its site, with respect to stability, anchoring of the load and accessibility in the limited space and under the special circumstances prevailing. It is therefore important that one component in the system consists of the special service vehicle defined in the claim. Such a custom-built service vehicle enables connection modules to be transported in an optimal and effective manner. According to a preferred embodiment of the system according to the invention the service bay is situated indoors, which offers additional advantages since the work can then be performed protected from wind and weather as well as facilitating the installation of fixed aids such as overhead cranes and the like. In another preferred embodiment the service bay is equipped with such aids and other service equipment, enabling the work to be performed effectively. The service bay according to this embodiment also includes a stock of spare parts and/or complete connection modules in reserve. When a connection module is to be repaired or serviced it can merely be transported out of the way and replaced by a similar module ready for use from stock. According to a further preferred embodiment of the system, a number of earthing points are arranged within the area of the switchgear, and the service vehicle can be connected optionally to any of these earthing points. During transport of a connection module in upright position, therefore, its stand part will be earthed while its apparatus part is separated from earth by the insulators. It can therefore be transported close to live modules, and even touch these, without risk of electric flashover. The above and other advantageous embodiments of the system according to the invention are defined in the sub-claims to claim 1. Corresponding advantageous embodiments of the method according to the invention are defined in the sub-claims to claim 9. According to a preferred embodiment the service vehicle has a frame which is open in one direction so that it can straddle the stand of a connection module, thereby enabling fast and simple loading of the module and stable transport . In a preferred variant of this embodiment the opening can be closed so that, when the stand of the module has been straddled, the vehicle has a closed frame thereby increasing its stability considerably. According to another preferred embodiment the service vehicle is provided with support members, vertically movable in relation to the frame, to facilitate lifting the connection module from its base plate when it is to be transported. The support member suitably comprises a pair of beams that are raised and lowered together. It is advantageous for the service vehicle to be designed with, on the one hand, a broad wheel base but, on the other hand, a narrow waist part. Stability during transport is then achieved, as well as flexibility to move between the modules in the switchgear station. To further increase its ability to turn around between the modules it is advantageous if the wheels can be steered individually. The above and other advantageous embodiments of the ser- vice vehicle according to the invention are defined in the sub-claims to claim 15. The invention will be explained in more detail in the following description of preferred embodiments, with referen- ce to the accompanying drawings in which Figures 1-3 show side views of various types of switchgear where the invention is applicable, Figure 4 is a schematic illustration of the principle for the layout of a system according to the invention Figure 5 shows a side view of a service vehicle with load according to one embodiment of the invention, Figure 6 is a section along the line VI-VI in Figure 5, Figure 7 shows a detail of the service vehicle according to Figure 5, Figure 8 illustrates the transport of a module according to a preferred embodiment of the invention. Figure 1 illustrates the layout of conventional switchge- ar, showing how the components in a row of apparatus are arranged. In a typical switchgear of this type three identical rows of apparatus are placed parallel with each other. The overhead power transmission lines 301 are supported by three pylons 302, 303, 304, one at each end of the row of apparatus and one in the middle. From left to right in the figure, the switchgear comprises the following units: a first group of three pillar stands 305, 306, 307, each carrying a busbar 308, 309, 310, which busbars are directed perpendicular to the plane of the figu- re, a first disconnector 311, a first breaker 312, a first current transformer 313, a second disconnector 314, a third disconnector 315, a second breaker 316, a second current transformer 317, a fourth disconnector 318, a fifth disconnector 319, a third breaker 320, a third cur- rent transformer 321, a sixth disconnector 322 and a second group of three pillar stands 326, 327, 328, each carrying a busbar 323, 324, 325. In this conventional arrangement the row of apparatus for 420 kV is approximately 120 meter m length. In Figure 2, showing a more compact arrangement of a switchgear from the same angle as Figure 1, the overhead power lines 101 are supported in the same way as above, by one pylon 102, 104 respectively, at each end of the row of ap- paratus and one pylon 103 in the middle. Here, too, stands 105-107 and 113-115 carrying busbars 108-110 and 116-118, respectively are arranged outermost at each end of the row of apparatus. Between these a first stand 111, a second stand 119 and a third stand 112 are arranged, each carrying a plurality of components including breakers and disconnectors. Such a multi-component stand is de- scribed in more detail in SE 9600123-5. Between the first multi-component stand 11 and the second multi-component stand 119 and between the second multi-component stand 119 and the third multi-component stand 112 is a space with a height of the dead zone above ground level that is higher than at the other parts of the line. Figure 3 shows yet another example of a switchgear where the invention is applicable. The row of apparatus here consists of only three units, i.e. three multi-component stands 202, 203, 204 similar to the equivalent stands in the layout according to Figure 2. The overhead power lines 200, 201 and busbars 205-210 are supported by a stand frame 211 located between the rows of apparatus with com- ponents. The Figure illustrates only one line and one such stand frame. The switchgear comprises two such stand frames 211 with a line at the side and outside each stand frame and a line located between them. To perform assembly of and service on one of the stands with its connection parts, i.e. a connection module, a system is used according to the invention as shown schematically in Figure 4. The connection modules are arranged within a switchgear area 1 and are arranged in rows in X and Y direction. Each connection module is secured in the ground at a base plate 2 constituting the erection site of the module. In the figure only a few of the connection modules 3 in the switchgear are shown schematically, whereas only the erection sites 2 have been marked for the others . If any of the connection modules in the switchgear needs repair or inspection, e.g. the module with base plate 2 as erection site, a service vehicle 4 is driven in to the switchgear area, up to the relevant connection module, the module then being loaded onto the service vehicle 4 in a manner to be described later. The Figure shows the service vehicle 4 which is constructed as a trailer drawn by a traction vehicle 5, on its way from the base plate 2a with its connection module 3a as load, heading for a ser- vice bay 6. The connection module 3a is transported in an erect position. The base plates 2 for erection of the connection modules are positioned relative each other so that the service ve- hide 4 has room to drive between them, at least along certain corridors, e.g. along the route A marked in the Figure for the service vehicle 4. The connection module 3a being transported and the connection modules 3 already in place are so adjusted to each other as to allow free passage for the connection module 3a being transported. The service vehicle 4 is earthed and, via the trailer, also the stand of the connection module being transported. Since its apparatus part is joined to the stand via insulators, the apparatus part can, without problem, move quite close to adjacent connection modules 3 and even touching some of them can be accepted. The connection module 3a is transported to a service bay 6 outside the area. The module can be repaired in the ser- vice bay and then transported back to its place in the switchgear station. However, it is even more suitable to simply exchange the connection module 3a for an identical module kept in stock as a complete unit at the service bay. The connection module 3a to be repaired is unloaded, after which the spare connection module 3b is loaded onto the trailer for transport out to the erection site 2a. The service bay 6 may be situated outdoors, but it is assumed to be more advantageous for it to be situated indo- ors or at least under cover. A stock of complete connection modules should be kept in reserve at the service bay, at least one of each type of connection module included in the switchgear station. Alternatively, or in addition, a stock of spare parts may also be kept in the service bay. Also provided at the service bay are overhead crane and other types of lifting gear and the tools and material necessary for repair and maintenance of the connection modules . The spare connection module 3b is arranged in a stand-by position in the service bay 6, erected on and anchored to a loose foot-plate 7 on the floor/ground of the service bay. It is so arranged that the service vehicle can reverse up to it and straddle the stand of the module for loading onto the trailer, as described below when descri- bing the service vehicle. Assembly of connection modules 3 can also be performed at the service bay 6 which is therefore equipped with base plate and contacts for disconnectors corresponding to tho- se at each connection module site in the switchgear station. When the connection modules have been assembled they are adjusted to the contact units. The resistance of the current path is checked and the factory-fitted control cables connected with plug-in contacts to a testing device so that the apparatus included can be tested as to function. Most of the measures required for installing a connection module at its site 2a in the switchgear station can thus be performed already in the service bay, thereby reducing the work out in the switchgear station to a mini- mum. After assembly, exchange, repair or service, the connection module is transported out to its erection site 2a. When the service vehicle 4 reaches the erection site or base plate 2 where the reserve connection module 3b is to be placed, it will fit without any adjustment since the base plate 2a and the contacts here correspond to those against which the connection module 3b has already been tested at the service bay 6. The control cables from the station may already be in place and terminate in plug-in connectors so all that has to be done is plug them directly into the control cable connection of the connection module 3b. Figure 5 illustrates the transport vehicle in the form of a trailer 4 loaded with a connection module 3a. The connection module 3a is a combined module comprising disconnectors 31, 32, breaker elements 33, 34 a central support insulator 35 and inclined operating insulators 36, 37 on each side of the latter, a control device 38 and a stand part 39. Other components, not shown, are also included in such a connection module. The design of the connection module per se does not constitute any central aspect of the present invention and reference is therefore only made to said SE-9600123-5 mentioned previously, for a more detailed description of such and similar combined connection modules. The connection module being transported may naturally be of conventional type containing only one apparatus . Figure 6, showing a view along the line VI-VI in Figure 5, illustrates a bird's-eye view of the service trailer 4. It comprises a frame 41 provided with wheels and comprising two parallel beams 52 placed relatively close together and running in the direction of movement of the trailer. At each end of the pair of beams 52 the frame widens considerably through a construction of inclined and transverse beams 53, 54, 58, 59 to provide a wide base for the pairs of wheels 42, 43, 44, 45 at each end. The two front wheels 44, 45 can be steered and are operated with the aid of a link mechanism connected to the pull rod 56. The tie bar can be angled, as shown by the position 56a indicated in broken lines, so that the front wheels turn. The rear wheels 42, 43 are normally locked in a straight position by the control sticks 57. Their two steering rods 61 can be connected together by a link 62. When the control sticks 57 are released from their locked position the rear wheels can be steered by means of these control sticks 57. Since all four wheels can be steered, extreme- ly narrow turns can be performed in narrow passages. This is also facilitated by the narrow waist at the middle of the trailer. All four wheels being controllable also facilitates fine adjustment of the trailer's position when fitting it against both the support beams 47 of the appa- ratus stand (during loading) and against the anchoring aperture of the base plate (during unloading) . The front end of the frame is provided with a cross bar 54 extending across the maximum width of the whole frame, whereas its rear end consists of two short cross bars 58, 59, aligned with each other and leaving an opening between them in the area between the parallel longitudinal beams 52. This opening can be closed by a cross bar 60 which is displaceable in the direction of the cross bars 58, 59. The Figure shows the cross bar 60 in closed position while its open positioned is marked with broken lines. The distance between the two longitudinal beams 52 is slightly greater than the width of the stand of a connection module. A connection module is loaded onto the trailer 4 by reversing the trailer in towards the stand of the module with the cross bar 60 open and so that the two longitudinal beams 52 straddle the stand. The trailer is reversed un- til the stand of the connection module 3a is mid-way between the wheel axles of the trailer, the support beams 47 being arranged to be higher up than the support members 46. The cross bar 60 can then be moved to its closed position so that the frame is closed and thus stable. The support member 46 is then raised to contact the support beams 47 of the stand, after which the four attachment points 46a are adjusted individually to the correct height level and the support beams 47 are screwed into the support member 46. When this has been done the stand 3a is detached from its base plate 2a out in the switchgear sta- tion or from the foot-plate 7 used for assembly at the service bay 6, after which the support member 46 is raised further to lift the entire connection module from its base plate. The connection module is thus ready for transport. The support member 46 is arranged to be able to lift the connection module in a plane which is displaced vertically in a strictly horizontal position. This is important since the connection module is extremely heavy and its centre of gravity is located high up, approximately 4 m. The connection module is sufficiently firmly anchored in the support member 46 and the support member in the frame 41, to be able to absorb the considerable bending moments in longitudinal and transverse direction which appear during transport as a result of the elevated centre of gravity of the connection module. Figure 7 illustrates how the support member 46 is raised and lowered. The support member 46 comprises two parallel mechanisms, each consisting of an upper beam 63 and a lo- wer beam 64 parallel thereto. The upper beam 63 in each mechanism constitutes the support surface for the support beams 47 of the stand. The two beams 63, 64 are joined to a front hinge 65 and a rear articulation means 66. The articulation means 65 and 66 are each articulately connec- ted to beam 63 and beam 64 and suspended in an articulated manner in the frame of the trailer. The front articulated means 65 is connected to a hydraulic cylinder 67 by means of which it can be turned about its articulation connected to the frame. The articulation means then forces the two beams 63, 64 to move closer or further away from each ot- her in a parallel movement, and the rear articulation means to follow this movement. The load-carrying surface of the support member 46 is thus lowered or raised. The two parallel mechanisms are raised and lowered synchronously. The hydraulic cylinder 67 is driven by a motor, or it may be pumped manually. Instead of the hydraulic cylinder 67 a worm gear may be used, which is operated manually or by a motor. Figure 8 illustrates schematically a connection module 3a during transport. The trailer 4 is connected to an earthing point 71 within the switchgear area by a flexible cable 70 that can be rolled up. The trailer and the stand part 72 of the module 3a are therefore earthed. The apparatus part of the module is insulated from earth by the support insulator 73 and may be brought close to surrounding live areas from adjacent modules which are in operation. The cable 70 is approximately 25 m long and when the full length of the cable has been utilized a second cable 76, shown rolled up, can be connected to the next earthing point 75 in the direction of travel. The first cable 70 is then disconnected from the earthing point 71 and the cable 70 rolled up on the trailer. At least one earthing point must always be connected. A number of such earthing points are thus arranged within the switchgear area, the distance between them being adjusted to the length of the cables 70, 76 so that the cables 70, 76 can be connected alternately to the earthing points. Although the connection modules described above are trans- ported in upright position, which is preferable for a number of reasons, transport of the modules in lying position or oriented in some other way is also feasible and within the scope of the invention.

Claims: C L A I M S 1. A system for assembly and maintenance of connection modules (3) in high-voltage switchgear (1) said switchgear comprising a plurality of such connection modules (3) with a plurality of such modules in both the X-direction and the Y-direction of the switchgear layout, characterized in that the system comprises a service vehicle (4), a service bay (6) and a base frame (2) for connection modules situa- ted in the vicinity of the switchgear (1), which service vehicle (4) is arranged to transport a connection module (3a), the service vehicle (4), connection modules (3) and the erection site of said base frame (2) being so adapted to each other that said service vehicle (4) can move wit- hin the switchgear area (1) while the switchgear is in operation. 2. A system as claimed in claim 1, wherein said service bay (6) is situated under cover, preferably indoors. 3. A system as claimed in claim 1 or claim 2, wherein said service bay (6) includes service equipment, assembly equipment, spare part stocks and/or complete reserve connection modules (3b) . 4. A system as claimed in claim 3, wherein at least one of said reserve connection modules (3b) is assembled in upright position on a foot plate (7) on the ground/floor so that the service vehicle (4) can be applied against the module in order to lift it. 5. A system as claimed in any of claims 1-4, wherein the service vehicle (4) and connection modules (3) in the switchgear and the positions for the base frames (2) are so adapted to each other that said mobility of the service vehicle (4) is possible along predetermined corridors (A) in the switchgear area. 6. A system as claimed in any of claims 1-5, wherein a number of earthing points are arranged within the area around the switchgear and wherein the service vehicle (4) is provided with conducting members connectable to the earthing points. 7. A system as claimed in any of claims 1-6, wherein the service vehicle (4) is arranged to transport a connection module (3a) in an erect position. 8. A system as claimed in claim 7, wherein the stand of the connection module (3a) being transported is earthed during transport and its connection part is insulated from earth by its insulators. 9. A method for assembly and maintenance of connection modules in high-voltage switchgear, said switchgear comprising a plurality of connection modules with a plurality of such modules in both the X-direction and the Y- direction of the switchgear layout, characterized in that assembly, repair or servicing of a connection module is performed in a service bay located outside the switchgear area and that this connection module is transported to or from its site by a service vehicle while the switchgear is in operation. 10. A method as claimed in claim 9, wherein assembly, repair and service of the connection modules is performed indoors . 11. A method as claimed in claim 9 or claim 10, wherein spare parts and/or complete reserve connection modules are available at said service bay. 12. A method as claimed m any of claims 9-11, wherein the service vehicle is moved along predetermined corridors in the switchgear area. 13. A method as claimed in any of claims 9-12, wherein the service vehicle is connected to any of a plurality of earthing points arranged within the area around the switchgear. 14. A method as claimed in any of claims 9-13, wherein the connection module is transported in an erect position. 15. A system component comprising a service vehicle (4) for use when performing the method as claimed n any of claims 9-14, characterized in that it is custom-built to be able to transport a complete connection module (3a) within a switchgear area (1) . 16. A service vehicle (4) as claimed in claim 15, comprising a support frame (41), which frame (41) is provided at least in one direction with a horizontally directed opening of sufficient width to permit it to straddle the stand of a connection module (3a). 17. A service vehicle as claimed in claim 16, wherein said opening s provided with a closing member (60) . 18. A service vehicle as claimed m claim 17, wherein said closing member (60) comprises a transverse bar (60) displaceable m its longitudinal direction. 19. A service vehicle as claimed in any of claims 15-18, provided w th a support member (46) for the connec- tion module, which support member (46) is vertically movable . 20. A service vehicle as claimed in claim 19, wherein said support member comprises two parallel beam elements (63), which are jointly movable in vertical direction. 21. A service vehicle as claimed in claim 20, wherein each beam element (63) constitutes one element in a parallelogram mechanism (63-66). 22. A service vehicle as claimed in any of claims 15-21, comprising a support frame carried by at least four wheels (42-45), said support frame (41) having a waist part with a width less than half the distance between two wheels . 23. A service vehicle as claimed in any of claims 15-22, provided with wheels (42-45) that can be individually controlled.

Inventors: LINDER TORBJOERN, SKOELD LEIF, LINDER, TORBJOERN, SKOELD, LEIF
Applicants: ASEA BROWN BOVERI, LINDER TORBJOERN, SKOELD LEIF, ASEA BROWN BOVERI AB, LINDER, TORBJOERN, SKOELD, LEIF
Application year: 1997
Main classification: H02B3
IPC codes: H02B1, H02B3, H03B5