Patent Publication Number: US-6215684-B1

Title: Feed-through for high and medium voltage station

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a feedthrough for a high-voltage or medium-voltage substation, including a voltage divider, a metal bar extending in a longitudinal direction above the voltage divider, and a metal coupling for mechanically and electrically connecting one end of the bar to the voltage divider. 
     A feedthrough of this kind is in particular erected on the ground under a high-voltage or medium-voltage line to pick up the current flowing in the line and, after dividing it, to feed it to protection or measuring equipment. In new generation feedthroughs the voltage divider is in the form of two cylindrical glass blocks separated by a metal electrode and the bar is erected on the top of the divider and rests on it. The mechanical and electrical connection between the bar and the voltage divider must be provided by a metal coupling and the object of the invention is to propose a solution for the manufacture of a coupling of this kind which uses few component parts and whose assembly is simple and reliable. 
     SUMMARY OF THE INVENTION 
     To this end, the invention consists in a feedthrough for a high-voltage or medium-voltage substation, including a voltage divider, a metal bar extending in a longitudinal direction above the voltage divider and a metal coupling for mechanically and electrically connecting one end of the bar to the voltage divider, the feedthrough being characterized in that the coupling comprises: 
     a flange with a boss fixed to the top of the voltage divider, the boss having a substantially frustoconical bore extending in the longitudinal direction inside which projects a substantially cylindrical central pin; and 
     a substantially frustoconical part constituting one end of the bar, this end being split in the longitudinal direction and having a cylindrical central bore, the part and the boss being shaped to be inserted one in the other. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     The invention will be better understood on reading the following description of an embodiment of the invention shown in the drawings. 
     FIG. 1 is a highly schematic axial section view of a feedthrough of the invention. 
     FIG. 2 is a more detailed axial section of the metal coupling between the bar and the voltage divider. 
     FIG. 3 is a more detailed axial section showing the fixing of the bar to the top of the feedthrough. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In FIG. 1, the feedthrough is shown as a support disposed on the ground and extending in a longitudinal and vertical axial direction D. It includes an electrically conductive metal bar  1 , for example an aluminum bar, which extends vertically inside a tubular insulative jacket  2 . The jacket can be of porcelain, for example. The jacket rests on a metal enclosure  3  resting on the ground. The ends of the jacket are equipped with fittings  4  and  5 , the fitting  5  anchoring the jacket to the enclosure. The fitting  4  anchors an electrical line (not shown) to the top of the feedthrough. 
     The bar  1  is electrically connected to the fitting  4  and to a voltage divider  6  inside the enclosure  3  on an earthed metal support  7 . The voltage divider  6  is made up of two cylindrical glass blocks stacked one on the other and separated by an electrode, not shown. 
     The bar  1  enters the interior of the enclosure  3  and its bottom end rests on the top of the voltage divider  6 . A metal coupling  8  connects the bar and the voltage divider electrically and mechanically. 
     As shown in FIG. 2, the metal coupling  8  comprises a metal flange  9  which is fixed to the top face of the voltage divider. The flange has a central boss  10  in which there is a substantially frustoconical bore  11  extending in the longitudinal direction, together with a substantially cylindrical central pin  12  extending in the axial direction D. The frustoconical bore  11  forms a kind of annular groove whose bottom is narrower than its mouth, the groove thus surrounds the central pin  12  which projects towards the bar in the direction D. 
     The coupling also has a substantially frustoconical part  13  which constitutes the end of the bar  1  in contact with the voltage divider. The part  13  is split in the direction D and is adapted to be inserted into the bore  11  in the flange. It has its own substantially cylindrical central bore  14  which extends in the axial direction D and in which the pin  12  engages. 
     The part  13  and the flange  9  are designed to be inserted one in the other with some resistance to insertion so as to assure a good electrical contact and an interference fit perpendicular to the direction D. In particular, the branches  15  of the frustoconical part must bear resiliently on the wall of the bore  11  when the part  13  is engaged in the boss  10  and there must be electrical contact between the pin  12  and the wall of the bore  14 . 
     Clearly, the part  13  and the bar  1  are cast or otherwise made in one part, as is the flange  9  with its boss  10 . 
     As shown in FIG. 3, the bottom end of the bar  1  is pressed against the voltage divider in the direction D by a set of spring washers  16  (or a spiral spring) mounted around a central pin  17  at the top end of the bar  1  to engage in a cylindrical bore  18  in the fitting  4 , for example. 
     The coupling in accordance with the invention therefore does not require the use of an insulative support to hold the bar inside the jacket  2 , the mechanical strength of the bar  1  being provided on the one hand by the coupling  8  and on the other hand by the pin  17 .