Patent Publication Number: US-2015070868-A1

Title: Shielding element for use in medium voltage switchgears, and method for manufacture the same

Description:
RELATED APPLICATIONS 
     This application claims priority as a continuation application under 35 U.S.C. §120 to PCT/EP2013/001413, which was filed as an International Application on May 14, 2013 designating the U.S., and which claims priority to European Application 12003826.0 filed in Europe on May 15, 2012. The entire contents of these applications are hereby incorporated by reference in their entireties. 
    
    
     FIELD 
     The present disclosure relates to a shielding element for use in medium voltage switchgears with vacuum interrupters having at least two contacts, which are movable along a switching path between closed and open contact positions. The shielding element is positioned around the contact position region in the vacuum interrupter. The present disclosure also relates to a method of making such a shielding element. 
     BACKGROUND INFORMATION 
     Vacuum interrupters can be equipped with inner shielding elements, surrounding the contact position in the closed and opened positions. 
     By using a profiled shielding for vacuum interrupters, it is possible to absorb more metal vapour for vacuum interrupters during switching, and thereby increase the interrupting capability, as disclosed in DE 19503347 A1. 
     In known configurations, if the profiled shielding is used, then the profile is tangential to the axis of shielding and needs to be made by machining, as disclosed in DE 19503347 A1. The profile is tangential to the shielding; therefore, the production method can only use machining, and the wall thickness for the shielding has to be thick, in order to have enough bulk material to get a profiled shielding after machining. 
     SUMMARY 
     An exemplary embodiment of the present disclosure provides a shielding element for a medium voltage switchgear with at least one vacuum interrupter having at least two contacts. The contacts are movable along a switching path between closed and open contact positions. The shielding element is positioned around a region of the contact position in the vacuum interrupter. The shielding element includes an inner surface having a topographic structure which is aligned parallel to the switching path of the contacts. 
     An exemplary embodiment of the present disclosure provides a method for manufacturing a shielding element for a medium voltage switchgear with at least one vacuum interrupter having at least two contacts. The contacts are movable along a switching path between closed and open contact positions. The exemplary embodiment includes positioning the shielding element around a region of the contact position in the vacuum interrupter, and forming an inner surface of the shielding element to have a topographic structure which is aligned parallel to the switching path of the contacts. In addition, the exemplary method includes forming the shielding element from at least one segment, which are manufactured as contoured cylindrical elements, and applying the topographic structure by deep drawing in a direction along a cylinder-long-axis of the shielding element. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Additional refinements, advantages and features of the present disclosure are described in more detail below with reference to exemplary embodiments illustrated in the drawings, in which: 
         FIG. 1  shows a perspective view of a shielding element according to an exemplary embodiment of the present disclosure; 
         FIG. 2  shows a cross-section of a groove of the shielding element according to an exemplary embodiment of the present disclosure; 
         FIG. 3  shows a cross-section of a groove of the shielding element according to an exemplary embodiment of the present disclosure; 
         FIG. 4  shows a cross-section of a groove of the shielding element according to an exemplary embodiment of the present disclosure; and 
         FIG. 5  shows a perspective view of the shielding element arranged in a vacuum interrupter, according to an exemplary embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Exemplary embodiments of the present disclosure, in comparison to known techniques, reduce the use of material in the construction of the shielding element, and at the same time, optimize the energy absorbance behavior of the shielding element. 
     In accordance with an exemplary embodiment, the inner surface of the shielding element has a topographic structure which is aligned parallel to the switching path of the contacts. 
     In accordance with an exemplary embodiment, the topographic structure of the inner surface of the shielding element is an alignment of parallel grooves. This arrangement causes an advantageous “folding” of the surface in the sense of an extension of the surface for absorption of energy. 
     In accordance with an exemplary embodiment, the cross section of the alignment of the grooves is in a Z-structure with sharp edges. 
     In accordance with an exemplary embodiment, the cross section of the alignment of the grooves is a wave-structure with round edges. 
     In accordance with an exemplary embodiment, the cross section of the alignment of the grooves is a U-structure with sharp edges. 
     All these topographic structures can be easily manufactured by deep drawing, because of the orientation of the structures. 
     According to an exemplary embodiment, in case of a sectionized shielding arrangement, at least the regions nearest to the contact positions can be structured in the above-described configurations. 
     In addition to the topographic structuring of the shielding element, each contact is mounted on a stem, and at least partial regions near to the contact piece can be additionally applied with topographic surface structures, in order to absorb energy from light arc occurrence. 
     In accordance with an exemplary embodiment, the backside of the electrodes, and/or the shielding plate, and/or the inner side of the end cover can be additionally applied with the above-described topography structure, in order to absorb the energy and vapor from arc. 
     An exemplary embodiment of the present disclosure provides a method for manufacturing such a shielding element. The method includes making the shielding to include at least one or more segments, which can be manufactured as contoured cylindrical elements as described above. The topographic structure is applied by deep drawing in the direction along the cylinder-long-axis of the shielding. 
     In the present disclosure, the profile is in the axial direction of shielding; therefore, the profile could be made by using deep drawing or protrusion during the production process, thin wall shielding could be also used; therefore with cost effective production for profiled shielding. 
     In accordance with the techniques of the present disclosure, the condensation surface of the metal vapor is increased, resulting in the following differences from known configurations: 1) the profile is in the axial direction to the shielding axis in parallel with the switching path axis, and 2) the production method by the present disclosure can utilize deep drawing and a protrusion process. This is contrary to known configurations, in which the profile can only be made by machining. Additional differences from known configurations include 3) by using this method the manufacture of shielding for “normal” vacuum interrupter without increase of costs for the vacuum interrupter and more secure for the performance of vacuum interrupters, and 4) this could be also for different materials, Cu, Cu/Cr, and Cu alloys. 
     An example of the profile of the present disclosure is shown in  FIG. 1 . It is to be understood that other kinds of profiles as in above mentioned patent application could be also used, such as those which can be oriented in the same way, parallel to the switching path axis of the contacts, so that the profile can be introduced into the inner shielding surface by deep drawing 
       FIG. 1  shows a perspective view of a shielding element  1  according to an exemplary embodiment of the present disclosure. In the exemplary embodiment of  FIG. 1 , the shielding element  1  can have the form of a contoured cylinder. In contrast to known configurations, the topographic structure  2  of the shielding element  1  is implemented as parallel aligned grooves. The orientation of the topographic structure  2  (e.g., the grooves) is consequently parallel to the contact movement axis (i.e., parallel to the switching path of the contacts of the vacuum interrupter). 
     Furthermore, as shown in  FIG. 1 , the shielding element  1  may contain dimples  3 , in order to facilitate positioning the shielding element  1 , including particular sections of the shielding element  1  based on the dimples  3 , inside the vacuum interrupter. 
       FIG. 2 ,  FIG. 3 , and  FIG. 4  respectively show cross sections of a groove of the shielding element  1 , according to exemplary embodiments of the present disclosure.  FIG. 2  shows a structure with a rectangular cross section  22  of the grooves with a flat outer line  23 .  FIG. 3  shows a waved structure with a rounded inner structure  24  of the grooves, and a rounded edge  25  on top.  FIG. 4  shows a sharp edged structure of the cross section of the grooves with a rectangular v-shaped structure  28 , sharp edges  29  on top and sharp edged baselines  27  of the grooves. 
     In accordance with an exemplary embodiment, the back side of the shielding element is not flat, as in  FIG. 2  or  3 , but is shaped with a structure  26  in the same way as on top. 
       FIG. 5  shows a perspective view of the shielding element  1  arranged in a vacuum interrupter, wherein the region of the stems  10  and  20  near the contact pieces and/or the shielding plate  50 ,  60  and/or the backside of the contact pieces and/or the inner side of the end covers  70  can be structured at least partly, in order, to result in the same function of high absorbance of energy. 
     It will be appreciated by those skilled in the art that the present disclosure can be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The presently disclosed embodiments are therefore considered in all respects to be illustrative and not restricted. The scope of the disclosure is indicated by the appended claims rather than the foregoing description and all changes that come within the meaning and range and equivalence thereof are intended to be embraced therein. 
     POSITION NUMBERS 
     
         
           1  shielding element 
           2  topographic structure 
           3  dimples 
           10  stem 
           20  stem 
           22  rectangular cross section 
           23  flat outer line 
           24  rounded inner structures 
           25  round edge on top 
           26  structure 
           27  sharp edged baselines 
           28  rectangular V-shaped structure 
           29  sharp edges on top 
           30  contact piece 
           40  contact piece 
           50  shielding plate 
           60  shielding plate 
           70  end cover