Patent Publication Number: US-9412543-B2

Title: ARC energy absorber

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a U.S. National Stage Application under 35 U.S.C. §371 of International Application No. PCT/EP2012/073676 filed on Nov. 27, 2012, and claims benefit to European Patent Application No. EP 11190985.9 filed on Nov. 28, 2011. The International Application was published in English on Jun. 6, 2013, as WO 2013/079464 A1 under PCT Article 21(2). 
     FIELD 
     The invention relates to a device for cooling exhaust gases caused by an electrical arc in high or medium voltage switch gear, which device comprises a housing with an inlet and an outlet for passage of the gases. 
     BACKGROUND 
     With high and medium voltage switch gear an accidental internal arc could occur. Such an arc is of high power and causes gases of high temperatures and a sudden increase in pressure in the housing for the switch gear. To relieve the pressure, a typical switch gear is usually provided with a blowout panel, which folds open by the high pressure of the arc. 
     If no other means are provided, then the hot gases would be blown out of the switch gear housing. In order to avoid damages to other objects and persons around the switch gear housing, sometimes an arc absorber is arranged in front of the blowout panel. Such an arc absorber contains ceramic elements with a plurality of parallel channels, through which the hot gases flow. Due to the large contact surface in the ceramic elements, heat of the gases is transferred into the ceramic elements, reducing the heat of the gases. Such a device for cooling exhaust gases is for example known from EP 1450458. 
     To have a sufficient cooling capacity with such ceramic elements a substantial length is required along which the gases are guided. 
     US 2009141432 describes a device for cooling hot gases caused by an accidental electric arc, which device has a number of plate like elements stacked together and spaced apart. The hot gases are guided through the channels between the elements. 
     The elements are provided with a layer of phase change material, like a metallic salt. When the metallic salt is heated by the hot gases, it will change phase from a solid state to a gas state. This phase change of the metallic salt will extract heat from the hot gases resulting in cooled gas. 
     Such a device is difficult to manufacture and it is difficult to ensure a good contact between the phase change material and the hot gases. 
     SUMMARY 
     An aspect of the invention provides a device for cooling one or more exhaust gases caused by an electrical arc in a high or medium voltage switch gear, the device comprising: a housing comprising an inlet and an outlet configured to allow passage of the exhaust gases; and a hydrous mineral comprising water, wherein the hydrous mineral is arranged in the housing, and wherein the hydrous mineral is suitable for cooling the exhaust gases with the water comprised in the hydrous mineral. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be described in even greater detail below based on the exemplary figures. The invention is not limited to the exemplary embodiments. All features described and/or illustrated herein can be used alone or combined in different combinations in embodiments of the invention. The features and advantages of various embodiments of the present invention will become apparent by reading the following detailed description with reference to the attached drawings which illustrate the following: 
         FIG. 1  shows a perspective view of a first embodiment of a device according to the invention; and 
         FIG. 2  shows a perspective view of a second embodiment of a device according to the invention. 
         FIG. 3  shows a schematic view of a third embodiment of a device according to the invention. 
     
    
    
     DETAILED DESCRIPTION 
     In a device according to the invention a hydrous mineral is arranged in the housing for cooling the gases with the water contained in the hydrous mineral. 
     Hydrous minerals are minerals containing water in their structure. The water is maintained in the mineral in the true structure of H 2 O. By heating the hydrous mineral, the water is forced out of the mineral and is freed to cool the gases of the accidental electric arc. 
     By using hydrous minerals a substantial amount of water can be maintained in the device, which is only released when necessary. The water has a substantial heat capacity, such that with a relative small housing comprising the hydrous mineral, a substantial heat capacity is provided for cooling the hot gases. 
     In a preferred embodiment of the device according to the invention the hydrous mineral is gypsum. 
     Gypsum is a typical low cost hydrous mineral, which can easily be used for a device according to the invention. The chemical formula of gypsum tells that two water molecules are bound to each molecule of calcium sulfate (CaSO 4 .2H 2 O). Because it contains water as a specific number of water molecules, gypsum is classified as a hydrous mineral, or hydrate. The water in the gypsum is not simply absorbed, but is chemically bonded into the atomic structure of the calcium-sulfate lattice. Thus, the water is not bonded as separate oxygen and hydrogen ions, but as integral water molecules that retain their characteristic composition and structure. 
     So, when the gypsum is heated to generally a temperature of above 150 degrees Celsius, the water molecules are forced out of the calcium-sulfate lattice. This freed water is then used for cooling the hot gases. 
     In a preferred embodiment of the device according to the invention at least one element having a plurality of channels, through which the exhaust gases are fed, is arranged in the housing and wherein the element comprises the hydrous mineral. 
     Such an element with a plurality of channels has the advantage of a large contact surface in a relative small element. Furthermore, these elements according to the invention could easily be used in housings according to the prior art as a replacement for the ceramic elements. 
     Preferably the at least one element is a rectangular cuboid and the plurality of channels are parallel and extend from one side of the cuboid to the opposite side. A rectangular cuboid is easy to stack together to provide a composed element with a desired heat capacity. 
     The element could be monolithic. The elements could for example be extruded from gypsum, similar to the manufacture of the ceramic elements. 
     In yet another preferred embodiment of the device according to the invention the housing is filled with hydrous mineral pellets. Pellets are easily made and a housing can simply be filled with the pellets by pouring the elements in the housing. Also, by filling the housing with pellets, it is ensured that a plurality of channels is obtained, through which the hot gases can flow. Furthermore, the pellets provide for a large contact surface. 
     The invention also relates to a switch gear housing for housing high or medium voltage electronic components, the housing comprising an outlet opening and a device for cooling exhaust gases according to the invention arranged in the outlet opening. 
     A preferred embodiment of the switch gear housing according to the invention, comprises a duct system arranged in the housing debouching in the outlet opening, wherein the device for cooling exhaust gases is arranged in the duct system. 
     The duct system ensures that the gases produced by an internal arc are guided to the outlet opening and thus through the device according to the invention. 
     In a further embodiment of the switch gear housing according to the invention the outlet opening is closed off by a blowout panel. 
     In  FIG. 1  a device  1  according to the invention is shown. The device  1  has a monolithic housing  2  with a plurality of parallel channels  3  running from a first side  4  to the opposite side  5 . The device  1  also includes gas cooling element  6  arranged in the monolithic housing  2 . The device  1  is preferably made of gypsum for example by extrusion. When hot gases G are guided through the channels  3 , heat is exchanged with the gypsum, such that water is freed, which will cool the hot gases. 
       FIG. 2  shows a second embodiment  20  of a device according to the invention. This device  20  has a housing  21  with a grating  22  in the front side and a grating  23  on the opposite back side. The housing  21  is furthermore filled with pellets  24  of a hydrous mineral, preferably gypsum. 
     Hot gas G enters the front grating  22  and swirls between the pellets  24 , such that heat is exchanged with the pellets  24  and water is freed to cool the hot gases G. 
       FIG. 3  shows a third embodiment  30  of a device according to the invention. This device  30  has a switch gear housing  31  for housing high or medium voltage electronic components, the switch gear housing  31  comprising an outlet opening  32  and a cooling device  40  for cooling exhaust gases according to the invention arranged in the outlet opening  32 . This device  30  also has a duct system  33  debouching in the outlet opening  32 , which is closed off by a blowout panel  34 . The cooling device  40  for cooling exhaust gases is arranged in the duct system. 
     While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. It will be understood that changes and modifications may be made by those of ordinary skill within the scope of the following claims. In particular, the present invention covers further embodiments with any combination of features from different embodiments described above and below. Additionally, statements made herein characterizing the invention refer to an embodiment of the invention and not necessarily all embodiments. 
     The terms used in the claims should be construed to have the broadest reasonable interpretation consistent with the foregoing description. For example, the use of the article “a” or “the” in introducing an element should not be interpreted as being exclusive of a plurality of elements. Likewise, the recitation of “or” should be interpreted as being inclusive, such that the recitation of “A or B” is not exclusive of “A and B,” unless it is clear from the context or the foregoing description that only one of A and B is intended. Further, the recitation of “at least one of A, B, and C” should be interpreted as one or more of a group of elements consisting of A, B, and C, and should not be interpreted as requiring at least one of each of the listed elements A, B, and C, regardless of whether A, B, and C are related as categories or otherwise. Moreover, the recitation of “A, B, and/or C” or “at least one of A, B, or C” should be interpreted as including any singular entity from the listed elements, e.g., A, any subset from the listed elements, e.g., A and B, or the entire list of elements A, B, and C.