Patent Publication Number: US-2023145027-A1

Title: Tee arrester with directional venting

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 17/175,056, filed Feb. 12, 2021, which claims the benefit of U.S. Provisional Patent Application No. 62/976,035, filed Feb. 13, 2020, the entire content of which is hereby incorporated by reference. 
    
    
     FIELD 
     The present disclosure relates to overvoltage protection assemblies, and more specifically, to tee-shaped surge arresters. 
     SUMMARY 
     Surge arresters are commonly used to protect underground high voltage electrical systems from power surges. Surge arresters include metal oxide varistor elements to provide a low or high impedance path depending on the voltage of the power system. During normal operation, the metal oxide varistor element has a high impedance, resulting in little current flowing through the surge arrester. However, if a power surge occurs, such as a surge resulting from a lightning strike, the impedance of the metal oxide varistor decreases. Surge current flows through the arrester to protect other components of the power system. However, the surge arrester may fail, creating an undesirable low impedance fault. If the surge arrester fails, then power frequency fault current flows through the arrester to ground. In this case the failed surge arrester is said to have faulted to ground. Surge arrester failures faulting to ground may be dangerous occurrences, as the fault current generates hot gasses, plasma, and electrical arcs, which are expelled from the device. 
     The current disclosure provides for a surge arrester that directs expulsion of MOV disks, gasses, and plasma away from potential human operators. A portion of the surge arrester may be angled such that the MOV disks, gasses, and plasma may be directed towards a wall, container, or the like. 
     In one embodiment, a surge arrester device comprises a first housing portion including a first end and a second end, the first end including a first opening and the second end including a second opening. The device includes a first axis parallel to the first housing portion, the first axis intersecting a first center of the first opening and a second center of the second opening, and a second axis perpendicular to the first housing portion, the second axis intersecting an intermediate section of the first housing portion. The device includes a second housing portion protruding from the intermediate section of the first housing portion, the second housing portion protruding at an angle between the first axis and the second axis, and a metal oxide varistor (MOV) stack within the second housing portion. The MOV stack is released through an opening of the second housing portion if the arrester faults to ground. 
     In some embodiments, the second housing portion includes a first end coupled to the first housing portion and a second end, the second end including the opening of the second housing portion. In some embodiments, the opening of the second housing portion includes a cap coupled to a group. In some embodiments, the surge arrester device is a tee-shaped surge arrester. In some embodiments, the surge arrester device is one selected from a group consisting of a tee arrester, a deadfront arrester, a lightning arrester, a bushing arrester, a 200 A loadbreak arrester, and a 600 A deadbreak arrester. In some embodiments, the surge arrester device includes an elastomeric primary insulation. In some embodiments, the first housing portion further includes a plug interface configured to receive an insulating plug via the first opening, and a bushing interface configured to receive a bushing via the second opening. In some embodiments, the insulating plug is integrated within the first housing portion. In some embodiments, the bushing is a transformer bushing of a transformer. In some embodiments, the transformer is one selected from a group consisting of a feedthrough transformer, a vault transformer, a pad-mounted transformer, a direct-buried transformer, and a submersible transformer. In some embodiments, the second housing portion protrudes at a 20° angle from the second axis. In some embodiments, the fault to ground condition is the result of a fault current within the surge arrester device being greater than a current threshold. 
     Another embodiment provides a high voltage electrical system. The high voltage electrical system comprises a transformer including a front plate, a plurality of connectors, and a plurality of arresters. Each of the plurality of connectors is coupled to an electrical phase of a plurality of electrical phases. Each of the plurality of arresters is coupled to one of the plurality of connectors, and a housing portion of each arrester of the plurality of arresters is angled towards the front plate. 
     In some embodiments, the plurality of electrical phases includes a first electrical phase, a second electrical phase, and a third electrical phase. In some embodiments, the plurality of connectors includes a first connector coupled to the first electrical phase, a second connector coupled to the second electrical phase, and a third connector coupled to the third electrical phase. In some embodiments, the plurality of arresters includes a first arrester coupled to the first connector, a second arrester coupled to the second connector, and a third arrester coupled to the third connector. In some embodiments, each electrical phase of the plurality of electrical phases is separated by a phase angle of approximately 120°. In some embodiments, each of the plurality of arresters includes a metal oxide varistor (MOV) stack, wherein the MOV stack is released through an opening of the housing portion based on a fault to ground condition. In some embodiments, the fault to ground condition is the result of a fault current within the respective surge arrester being greater than a current threshold. In some embodiments, each of the plurality of arresters is one selected from a group consisting of a tee arrester, a deadfront arrester, a lightning arrester, a bushing arrester, a 200 A loadbreak arrester, and a 600 A deadbreak arrester. In some embodiments, the transformer is one selected from a group consisting of a feedthrough transformer, a vault transformer, a pad-mounted transformer, a direct-buried transformer, and a submersible transformer. In some embodiments, an opening of the housing portion includes a cap coupled to a ground. 
     Other aspects of the application will become apparent by consideration of the detailed description and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    illustrates a perspective view of a surge arrester, according to some embodiments. 
         FIG.  2    illustrates a cross-sectional side view of the surge arrester of  FIG.  1   , according to some embodiments. 
         FIG.  3    illustrates a transformer power system, according to some embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     Before any embodiments of the application are explained in detail, it is to be understood that the application, and the devices and method described herein, are not limited in their application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The devices and methods in this application are capable of other embodiments and of being practiced or of being carried out in various ways. 
       FIGS.  1  and  2    illustrate a surge arrester  100  (e.g., a tee arrester, a deadfront arrester, a lightning arrester, a bushing arrester, a 200 A loadbreak arrester, a 600 A deadbreak arrester, or the like) according to some embodiments. The surge arrester  100  includes a housing  102  that includes a first housing portion  104  and a second housing portion  106 . The housing  102  may be composed of an insulating material to protect external equipment and workers from high voltages that may be present within the surge arrester  100 . For example, the housing  102  includes an elastomeric conductive shell  108  and an elastomeric primary insulation  110 . The elastomeric conductive shell  108  may be composed of, for example, a conducting EPDM. The elastomeric primary insulation  110  may be composed of, for example, an insulating EPDM. In some embodiments, all components other than electrical connection points may be insulated such that they are electrically shielded. 
     The first housing portion  104  includes a first opening  112  at a first end of the first housing portion  104  and a second opening  114  at a second end of the first housing portion  104 . The first housing portion  104  includes a plug interface  116  configured to receive an insulating plug, reducing tap plug, reducing tap well, or connecting plug via the first opening  112 . In some embodiments, the insulating plug, reducing tap plug, reducing tap well, or connecting plug is integrated within the arrester housing  104 , such that there is no opening  112  or interface  116  and the plug and housing are molded as one unit. The first housing portion  104  includes a bushing interface  118  configured to receive a bushing via the second opening  114 . The bushing may be, for example, a 600 A standard shaped bushing. The bushing may be configured to couple the surge arrester  100  with an underground power system, such as a 15 kV, 25 kV, 28 kV, or 35 kV underground system. The first housing portion  104  also includes an elastomeric conductive insert  120  and a metallic connector spade  122 . The metallic connector spade  122  couples the plug interface  116  to the bushing interface  118 . Additionally, should an insulating plug be located within the plug interface  116 , the insulating plug may couple to a bushing within the bushing interface  118  via the metallic connector spade  122 . 
     The first housing portion  104  includes a longitudinal (e.g., first) axis  124  parallel to the first housing portion  104 . The longitudinal axis  124  passes through the first housing portion  104 , intersecting the first housing portion  104  at a center of the first opening  112  and at a center of the second opening  114 . The first housing portion  104  further includes a latitudinal (e.g., second) axis  126  perpendicular to the longitudinal axis  124 . The latitudinal axis  126  intersects the first housing portion  104  at an intermediate section of the first housing portion  104 . 
     The second housing portion  106  protrudes from the intermediate section of the first housing portion  104  and includes a metal oxide varistor (MOV) stack  128  and a ground connection assembly  130  coupled to a system ground  132 . The second housing portion  106  protrudes from the first housing portion  104  at an angle between the longitudinal axis  124  and the latitudinal axis  126 . For example, the second housing portion  106  may protrude from the first housing portion  104  at a 20° angle form the latitudinal axis  126 . The first housing portion  104  and the second housing portion  106 , in combination, form a general “T” shape. 
     The ground connection assembly  130  includes a fastener  134  that couples the MOV stack  128  to the system ground  132 . The ground connection assembly  130  may further include a cap configured to disconnect the ground connection assembly  130  from the second housing portion  106  upon a failure of the surge arrester  100 . In some embodiments, the cap includes a hole configured to allow hot gas to escape the housing  102 . 
     The MOV stack  128  is coupled to the ground connection assembly  130  to provide an electrical connection between the system ground  132  and the metallic connector spade  122 . In some embodiments, the MOV stack  128  is composed of several MOV disks joined into a single assembly. The MOV stack  128  has a resistance that changes based on the voltage of the surge arrester  100 . At a normal operating voltage, the MOV stack  128  has a high resistance and restricts current from flowing through the surge arrester  100 . In the case of a power surge (e.g., a lightning strike, a voltage increase, etc.), the resistance of the MOV stack  128  decreases and allows current to flow through the surge arrester  100  to the system ground  132 . For example, when the current becomes greater than a current threshold (i.e., maximum current of the MOV stack  128 ), the surge arrester  100  begins to fail (i.e., fault to ground). When this occurs, the MOV stack  128  releases heat and, as the power surge continues for a period of time, the MOV stack  128  may continue to release dangerous hot gas and build up pressure. In some embodiments, when the dangerous hot gas builds enough internal pressure, the cap or plug of the ground connection assembly  130  may release, allowing the flames, plasma, arcing, hot gas, and MOV stack  128  to escape the housing  102 . 
       FIG.  2    illustrates a three-phase apparatus, such as a switchgear or transformer  200  (e.g., a feedthrough transformer, a vault transformer, a pad-mounted transformer, a direct-buried transformer, a submersible transformer, and the like) according to some embodiments. The transformer  200  includes a front plate  201  situated at the end of a radial underground run. The transformer  200  includes tee connectors  204   a ,  204   b , and  204   c  connected to a first electrical phase  202   a , a second electrical phase  202   b , and a third electrical phase  202   c . The first electrical phase  202   a  may be an A phase, the second electrical phase  202   b  may be a B phase, and the third electrical phase  202   c  may be a C phase. Each phase  202   a ,  202   b ,  202   c  may be separated by a phase angle of approximately 120°. Each phase  202   a ,  202   b ,  202   c  connect to the tee connectors  204   a ,  204   b ,  204   c  via a transformer bushing, such as a 600 A deadbreak integral transformer bushing. 
     The tee connectors  204   a ,  204   b ,  204   c  are connected to tee arresters  206   a ,  206   b ,  206   c  respectfully. The tee arresters  206   a ,  206   b ,  206   c  are each, for example, the surge arrester  100 . The tee arresters  206   a ,  206   b ,  206   c  each have a bottom plate  208   a ,  208   b ,  208   c  connected to the system ground  132  (not shown). Additionally, the tee arresters  206   a ,  206   b ,  206   c  include the second housing portion  106  angled such that the bottom plate  208   a ,  208   b ,  208   c  faces the front plate  201 . In the case the current through the tee arresters  206   a ,  206   b ,  206   c  passes a current threshold such that the MOV stack  128  melts and releases hot gas, the MOV stack  128  expulsion is directed towards the front plate  201 . 
     Thus, the application provides, among other things, a tee-shaped surge arrester. Various features and advantages of the application are set forth in the following claims.