Abstract:
An interruption and disconnecting device for high or medium voltage applications including a disconnection chamber and an interruption pole having a casing that delimits a free volume accommodating an interruption chamber. The interruption chamber contains a moving contact and a fixed contact. The interruption pole and the disconnection chamber contain dielectrically insulating fluids. The interruption chamber is sealed with respect to a remaining part of the interruption pole.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an interruption and disconnecting device for high- and/or medium-voltage applications, which contains dielectric insulation means and has a particular structure, so as to allow the reduction of the environmental impact of said insulation means. 
     2. Description of the Related Art 
     It is known that the interruption and disconnecting devices of the art generally comprise at least one interruption chamber and a disconnection chamber which are connected to insulating bushings. These elements are arranged inside a structure which is sealed with respect to the surrounding environment and is filled with a fluid insulating medium. With reference to FIG. 1, a block diagram is presented which illustrates an example of a typical structure of a known interruption and disconnecting device used in a high-voltage substation. 
     A conductor of a main power line, indicated by the arrow  2 , is connected to a main distribution bar  3  by means of the interruption and disconnecting device  1 . Said interruption and disconnecting device  1  comprises an insulating bushing  4  for connection to the line  2 . a disconnection chamber  5 , an interruption chamber  6 , electric current measuring devices  7  and  8  arranged at the ends of the interruption chamber  6 , and an insulating bushing  9  for connection to the bar  3  by means of a conductor  10 . There are also two devices  11  and  12  used to earth the system. 
     The disconnection chamber  5  can be arranged both upstream and downstream of the interruption chamber  6 . 
     The device  1  is completely filled with an insulating medium in order to prevent electrical discharges between the various parts that are at high potential differences. 
     A known embodiment of an interruption and disconnecting device according to the block diagram of FIG. 1 is presented with reference to FIG.  2 . The insulating bushings  4  and  9  are arranged respectively in input and in output with respect to the interruption and disconnecting device  1 . The insulating bushing  4  contains the conductor  2  of the main power line, while the insulating bushing  9  contains the conductor  10  connected to the main distribution bar (not shown in FIG.  2 ). 
     The insulating bushing  4  is connected to the disconnection chamber  5  by means of a coupling  13 . The disconnection chamber  5  contains a fixed contact  14  and a moving contact  15  for performing disconnection. An earthing device  11  is also connected to the chamber  5  and connects, if required, the main conductor  2  to the outer casing,  16  of the device  1 , which is at ground potential by means of the supports  17 ,  18  and  19 . Actuation elements  20  for moving the moving contact  15  are also placed inside the disconnection chamber  5 . The disconnection chamber  5  is furthermore separated from the insulating bushing  4  and from the disconnection chamber  6  by means of the insulating partitions  21  and  22 . 
     The interruption chamber  6  contains a moving contact  23  and a fixed contact  24 . The moving contact  23  is actuated by movement elements  25 . Further, the earthing device  12  is connected to the interruption chamber  6  and places the conductor  26  in output from the disconnection chamber at ground potential. The moving contact  23  is connected to the conductor  10  in output from the interruption and disconnecting device  1 . The interruption chamber  6  is separated from the insulating bushing  9  by means of the insulating partition  28 . The insulating bushings  4  and  9 , the interruption chamber  6  and the disconnection chamber  5  are completely filled with an insulating fluid, generally sulfur hexafluoride (SF 6 ), having a pressure which is higher than the atmospheric one. In order to maintain said internal pressure, required in order to achieve reduced insulation distances and therefore reduce the dimensions of the structure. the device  1  is completely sealed with respect to the outside environment. 
     Alternative configurations with respect to the one described in FIGS. 1 and 2 are possible. In particular, it is possible to use multiple disconnection chambers and multiple insulating bushings if it is necessary to connect multiple distribution bars to the main power line. 
     In the interruption and disconnecting devices of the art, the insulation fluid that is generally used is sulfur hexafluoride (SF 6 ). Other known fluids are fluorocarbons (FC), perfluorocarbons (PFC), perfluoropolyethers (PFPE) or mixtures thereof. 
     The use of these insulation means, particularly SF 6 , which has the highest dielectric insulation capacity, allows to considerably reduce the insulation distances and therefore to considerably reduce the dimensions of each single device, and therefore of the substation in which it is used, with respect to the use of insulating means, such as mineral oils. This fact leads to a considerable reduction in installation and operating costs. 
     It is known from the technical literature that known fluoridized gaseous insulating means, in particular SF 6 , may cause problems in terms of environmental impact; furthermore they are considerably expensive. 
     Reducing the content of these insulating means by using alternative dielectric fluids, such as for example mixtures of SF 6  and nitrogen (N 2 ), pure nitrogen or noble gases leads to an increase in the required insulation distances, since said alternative fluids have, for an equal pressure, a much lower dielectric strength and arch quenching power than, for example, SF 6  used in its pure state. Simple replacement of SF 6  with other alternative insulation fluids without performing any structural modification to the interruption and disconnecting device would cause malfunctions. 
     On the other hand, if the pressure of said alternative insulating fluids is increased so as to ensure satisfactory dielectric strength and arc quenching power, it is necessary to resort to complicated structures which are economically scarcely competitive and scarcely reliable. 
     BRIEF SUMMARY OF THE INVENTION 
     The aim of the present invention is to provide an interruption and disconnecting device for high- and/or medium-voltage applications, whose structure has a reduced complexity and is capable of optimizing the use of the insulation means used, so as to considerably reduce their environmental impact. 
     Within the scope of this aim, an object of the present invention is to provide an interruption and disconnecting device for high- and/or medium-voltage applications. which has a modular structure which allows to partition the volume of the insulating fluids used inside the interruption pole. 
     Another object of the present invention is to provide an interruption and disconnecting device for high- and/or medium-voltage applications, in which it is possible to use different insulation means inside the interruption pole. 
     Another object of the present invention is to provide an interruption and disconnecting device for high- and/or medium-voltage applications, which allows easy maintenance and/or replacement of the electric actuation elements, particularly of the parts that are most exposed to wear, such as the fixed contact and the moving contact of the interruption chamber. 
     Another. but not last, object of the present invention is to provide an interruption and disconnecting device for high- and/or medium-voltage applications. which is highly reliable and relatively easy to manufacture and at competitive costs. 
     This aim. these and other objects, which will become more apparent hereinafter, are achieved by an interruption and disconnecting device for high- and/or medium-voltage applications, comprising a disconnection chamber and an interruption pole having a free volume accommodating an interruption chamber which contains a moving contact and a fixed contact, said interruption pole and said disconnection chamber containing dielectrically insulating fluids. The device according to the invention is characterized in that said interruption chamber is sealed. 
     In this way. the device according to the invention has a modular structure which allows to optimize the use of dielectric fluids and to reduce the environmental impact; in fact, the dielectric fluids which have a high environmental impact are used only in the sealed interruption chamber where a high arc quenching power is required. 
     Another advantage of the device according to the invention, consists in the fact that the interruption chamber can be extracted from the main body of the electric interruption pole. This allows easy maintenance and/or replacement of the parts most subject to wear during the interruption and disconnection actuations by virtue of the possibility to extract the sealed interruption chamber from the body of the electric pole. Furthermore, the device according to the invention is constituted by a relatively small number of parts and ensures high reliability and easy execution. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Further characteristics and advantages of the invention will become more apparent from the description of some preferred but not exclusive embodiments of an interruption and disconnecting device according to the invention, illustrated by way of non-limitative example in the accompanying drawings, wherein: 
     FIG. 1 is a block diagram of an example of a known interruption and. disconnecting device for high-voltage applications: 
     FIG. 2 is a schematic example of embodiment of an interruption and disconnecting device for high-voltage applications; 
     FIG. 3 is a preferred but not exclusive embodiment of an interruption and disconnecting, device according to the present invention; and 
     FIG. 4 illustrates schematically an alternative embodiment of an interruption and disconnecting device according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As illustrated in FIG.  3 . the interruption and disconnecting device according to the invention comprises an input insulating bushing  51  which is electrically connected to a main power line  50 . A transformer  53  is generally placed at the base of the insulating bushing  51  in order to measure the current in input to the device. The insulating bushing  51  is connected to an intermediate chamber  55  and is insulated from it by means of the partition  56 . 
     The intermediate chamber  55  and the insulating bushing  51  are filled with a dielectric fluid having a very low environmental impact or even non-impact at all. for example a gaseous mixture of sulfur exafluoride and nitrogen (SF 6 +N 2 ), or pure nitrogen gas (N 2 ), or air. 
     The intermediate chamber  55  is connected to an interruption pole  54  and is insulated from it by means of the partition  57 ; in its turn, the interruption pole  54  is structurally connected to a disconnection chamber  67  by means of the partition  73 . The interruption pole  54  has a free volume, delimited by its casing  200  and the partitions  73  and  57 , which accomodates an interruption chamber  63 . 
     Said interruption chamber  63  contains interruption mechanisms which comprise at least a fixed contact  64  and at least a moving contact  59 . The moving contact  59  is rigidly coupled to a guiding rod  61  which is moved by an actuation system  62 . for example of the linking rod-crank type; the fixed contact  64  is connected to the disconnection chamber  67  by means of a sealed connection  66 . 
     As illustrated. the actuation system  62 , the guiding rod  61  of the moving contact. the moving contact  59  and the fixed contact  64  are arranged inside the casino, of the interruption chamber  63 ; said casing of the chamber  63  can be made of insulating material, for example fiberglass-reinforced plastic. at least in the part that surrounds the moving contact  59 , the fixed contact  64  and the rod  62 . Field shields  68  and  69  are positioned around the casing of the interruption chamber  63 ; alternatively, the casing of the interruption chamber  63  can be used in its end part as field shield, without having to use the field shield  69  and the closure flange  72 . 
     The interruption chamber  63  is hermetically closed, in one end portion, by a flange  72  and is connected, at the opposite end, to the casing of the interruption pole  54  by means of the sealing flange  65 ; the casing, of the interruption pole  54  i can be made, for example. of conducting plastic. 
     In this way. the interruption chamber  63  is advantageously sealed with respect to the remaining parts of the interruption pole  54 . As a consequence, the interruption chamber  63  can be filled with a highly dielectric fluoridized fluid, preferably sulfur exafluoride (SF 6 ), by means of the valve  71 , while the interruption pole  54  is filled by means of the valve  74 , in the part of the free volume that is not occupied by the chamber  63 , with a different dielectric fluid, such as for example a gaseous mixture of sulfur exafluoride and nitrogen (SF 6 +N 2 ), or pure nitrogen gas (N 2 ), or air. Alternatively, the interruption chamber  63  can be filled with a dielectric fluoridized fluid chosen among the group constituted by perfluoropolyethers (PFPE), or perfluorocarbons (PFC), or fluorocarbons (FC). 
     This solution is particularly advantageous in that it allows to segregate the. insulation means which have a high arc quenching power, but a high environmental impact as well, only where it is strictly necessary, that is to say, inside the casing of the interruption chamber  63  at the moving contact and at the fixed contact. In this manner the volume of potentially polluting means used in the device is minimized. 
     Furthermore, their segregation inside the sealed chamber  63  allows adequate control and prevents their dispersion into the atmosphere. In fact, the intermediate chamber  55  comprises a first portion of a piston-operated protection system  58  which interrupts the electrical connection to the main power line if a pressure loss of the dielectric fluid used in the interruption pole  54  occurs. A second portion of the piston-operated protection system  58  is positioned inside the interruption pole  54  and is connected to the moving contact  59  of the interruption chamber  63  by means of a sealed connection  60 . According to an alternative embodiment, the conductor  50  of the insulating bushing  51  can be directly connected to the interruption chamber  63 . 
     A further advantage resides in the fact that, by acting on the connections  60  and  66  and on the flange  65 , the interruption chamber  63  can be extracted from the interruption pole  54  by acting in the direction of the arrow  70 . 
     This solution is advantageous in that it allows to fully replace the chamber  63  if the parts subjected to the most intense wear, that is to say, the moving contact  59  and the fixed contact  64 , are damaged. considerably facilitating maintenance of the device. 
     The disconnection chamber  67  contains a moving contact  75  which, by means of a movement system  76 , for example of the rack type, can be connected to a first fixed contact  77  or to a second fixed contact  78 . The first fixed contact  77  connects the moving contact  75  to the output insulating bushing  80 , while the second fixed contact  78  connects the moving contact  75  to the outer casing  79 , of the disconnector chamber  67 , which is at ground potential. The actuation system  76  is actuated by an actuator  81 , for example an electric motor. The insulating bushing  80  is separated from the disconnection chamber  67  by means of a partition  82 ; a transformer  83  is generally placed at the base of the through conductor  80  and measures the current in output from the device. 
     The disconnection chamber  67  and the insulating bushing  80  are filled with a dielectric fluid having a very low environmental impact, or even non-impact at all, such as for example a gaseous mixture of sulfur exafluoride and nitrogen (SF 6 +N 2 ), or pure nitrogen gas (N 2 ), or air. 
     The interruption and disconnecting device according to the invention is particularly suitable for use in high- and/or medium-voltage substations for distributing and transmitting electric power. Accordingly, the present invention also relates to a high- and/or medium-voltage substation for distributing and transmitting electric power, characterised in that it comprises an interruption and disconnecting device according to the invention. 
     With reference to FIG. 4, an alternative embodiment of the device according to the invention is schematically illustrated by indicating only the path of the current. In particular, the embodiment of FIG. 4 foresees the use of an interruption pole  89 , a sealed interruption chamber  90  and three insulating bushings  91 ,  92  and  93 . 
     The interruption chamber  90  is preferably filled with sulfur exafluoride SF 6 , while the remaining volume of the interruption and disconnecting device is filled with insulating means having a very low environmental impact, or even non-impact at all, such as for example a mixture of sulfur exafluoride and nitrogen (SF 6 +N 2 ), or pure nitrogen gas (N 2 ), or air. As regards the constructive details, reference can be made for example to FIG.  3 . This embodiment is advantageous in that it allows to connect the device to multiple secondary. distribution bars for example in a substation. 
     In practices it has been found that the device according to the invention fully achieves the intended aim, since, thanks to the modularity of its structure, it is possible to minimize the pollution potential of the interruption and disconnecting device by segregating the insulating means which have a high environmental impact only at the parts that require a higher arc quenching power. 
     The device thus conceived is susceptible of modifications and variations, all of which are within the scope of the inventive concept; for example, it is possible to use multiple interruption chambers. In any case, however, the advantages encountered in the above described embodiments of the invention are maintained. 
     All the details may furthermore be replaced with technically equivalent elements. In practice, the considered circuit configurations, so long as they are compatible with the specific use, as well as the single components, may be any according to requirements and the state of the art.