Patent Document

BACKGROUND 
       [0001]    The present invention relates to switchgear interrupters and, more specifically, to voltage sensing at an interrupter. 
         [0002]    An interrupter for a switchgear system can include a vacuum interrupter for fault interruption. A vacuum interrupter can be viewed or thought of as a ceramic bottle with two mechanical contacts sealed inside a vacuum. Fault interruptions are performed in the vacuum by the interrupter. 
       SUMMARY OF THE INVENTION 
       [0003]    Before and after an interruption is performed it is useful to sense the voltage at the interrupter. Some dielectric switchgear systems provide voltage sensing on one side of an interrupter—either the source side or the load side—but not both. Detecting voltages on both the load side and the source side of an interrupter in a switchgear system when the interrupter is in an open position can be beneficial for some applications such as network reconfiguration and distribution automation. Some embodiments of this invention provide a solid dielectric interrupter with two voltage sensing systems imbedded together inside one module for a single phase application. 
         [0004]    In one embodiment, the invention provides an interrupter system for a switchgear. The interrupter system includes a source-side conductor, a load side conductor, and an interrupter. A source-side voltage detector is positioned proximate to the source-side conductor and a load-side voltage detector is positioned proximate to the load-side conductor. An insulating overmold encases both conductors, both voltage detectors, and the interrupter. A controller is coupled to both of the detectors and is configured to detect a source-side voltage and a load-side voltage. 
         [0005]    In some embodiments, the voltage detectors include cylindrical voltage screens positioned around each conductor in a coaxial arrangement. The controller senses a capacitance between the voltage screen and the corresponding conductor and determines a voltage based on the sensed capacitance. 
         [0006]    In some embodiments, the exterior surface of the overmold is covered with a grounded conductive coating such a metallic paint. 
         [0007]    Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a perspective view of an interrupter system according to one embodiment. 
           [0009]      FIG. 2  is a perspective view of the interrupter system of  FIG. 1  encased in an overmold. 
           [0010]      FIG. 3  is a perspective view of an interrupter system according to a second embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. 
         [0012]      FIG. 1  shows the interrupter system  100  according to one construction. A vacuum interrupter  101  is positioned between a top-side conductor  103  and a bottom-side conductor  105 . In this example, the top-side conductor  103  is a source side conductor while the bottom side conductor  105  is a load-side conductor. However, in other embodiments, this orientation may be reversed. A source-side voltage detector is positioned proximate to the top-side conductor. The source-side voltage detector includes a first cylindrical voltage screen  107  positioned around the top-side conductor  103  in a coaxial arrangement at a distance of approximately 17 mm from the surface of the top-side conductor  103 . A reinforcement ring  109  assists in positioning the first voltage screen  107  when an overmold is applied to the interrupter system (as described in detail below) and also provides an electrical connection to the first voltage screen  107 . Both the first voltage screen  107  and the reinforcement ring  109  are made of a conductive metal such as, for example, aluminum and may be welded together. 
         [0013]    During operation, a current is applied through the top-side conductor  103 , the interrupter  101 , and the bottom-side conductor  105 . The first voltage screen  107  and the top-side conductor  103  form a capacitor. The capacitance between the first voltage screen  107  and the top-side conductor  103  depends upon the voltage applied to the top-side conductor  103 . Therefore, the voltage of the top-side conductor  103  is determined by sensing the capacitance between the top-side conductor  103  and the first voltage screen  107 . The calculation of the voltage of the top-side conductor  103  can be performed by a variety of systems such as a controller located proximate to the interrupter system, a remote computer system, or an ASIC. 
         [0014]    Similarly, a load-side voltage detector includes a second cylindrical voltage screen  111  positioned around the bottom-side conductor  105 . The capacitance between the second voltage screen  111  and the bottom-side conductor  105  is used to determine a voltage of the bottom-side conductor  105 . Because voltage sensing systems are arranged proximate to both the top-side conductor  103  and the bottom-side conductor, the system is able to measure a voltage on either side of the interrupter  101  even when the interrupter  101  is in the open position. 
         [0015]    The interrupter system illustrated in  FIG. 1  also includes a current transformer  113  placed around the bottom-side conductor  105 . Cables and wiring from the current transformer  113  and the second voltage screen  111  are housed in a protection pipe  115 . 
         [0016]    The interrupter system  100  illustrated in  FIG. 1  is housed within a single overmold as illustrated in  FIG. 2 . The encased system also includes a top-side bushing  119  and a bottom-side bushing  121 . The bushings  119 ,  121  are molded as part of the same overmold  117  and are used to connect power cables to the top-side conductor  103  and the bottom-side conductor  105  of the interrupter system  100 . In other embodiments, the bushings  119 ,  121  are formed as separate pieces that are attached to the overmolded interrupter system  100 . 
         [0017]    As illustrated in  FIG. 2 , the protective pipe  115  that houses the cables and other wiring from the second voltage screen  111  is encased within the overmold  117 . A cable  123  is coupled to the first voltage screen  107  through the reinforcement ring  109  after the overmold  117  is applied. 
         [0018]    The overmold  117  consists of an insulating material that is applied by a molding process. The exterior of the overmold  117  is covered with a conductive paint on all surfaces except the top-side bushing  119  and the bottom-side bushing  121 . The conductive paint is grounded when the interrupter system  100  is in operation. Grounding the conductive paint on the exterior surface of the overmold  117  provides a fixed grounding reference for the voltage screens  107 ,  111  and prevents the voltage readings from floating. 
         [0019]    In other constructions, the overmold  117  is covered in another conductive or semiconducitve material that may not cover as much surface area of the overmold  117 . For example, in the construction illustrated in  FIG. 3 , a top-side conductive sleeve  125  is fixed on the outside of the overmold  117  adjacent to the first voltage screen  107 . Similarly, a bottom-side conductive sleeve  127  is fixed on the outside of the overmold  117  adjacent to the second voltage screen  111 . Each voltage sleeve  125 ,  127  is electrically coupled to ground to provide a fixed reference voltage for the corresponding voltage screen  107 ,  111 . 
         [0020]      FIG. 3  also further illustrates the connections of cable  123  on the exterior of the overmold  117 . The cable  123  is connected to the top screen  107  through an upper strain relief connector  129 . The upper strain relief connector  129  has a 90-degree downward angle mounted on the exterior of the overmold  117 . The cable  123  extends from the upper strain relief connector  129  to a lower strain relief connector  131  mounted on a switch gear housing  133  near the bottom of the interrupter system  100 . The upper and lower strain relief connectors  129 ,  131  maintain tension in the cable  123  while keeping the cable  123  appropriately connected. The upper and lower strain relief connectors  129 ,  131  also prevent water or moisture from entering the interrupter system  100  and the switchgear housing  133 . 
         [0021]    Thus, the invention provides, among other things, an interrupter system encased in a single insulating overmold capable of measuring voltages on both the source side and the load side whether the interrupter is opened or closed. Various features and advantages of the invention are set forth in the following claims.

Technology Category: 5