Patent Publication Number: US-2023141161-A1

Title: Vacuum interrupter anti-bounce dampener

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of priority from the U.S. Provisional Application No. 63/278,217, filed on Nov. 11, 2021, the disclosure of which is hereby expressly incorporated herein by reference for all purposes. 
    
    
     BACKGROUND 
     Field 
     This disclosure relates generally to an anti-bounce dampener assembly for dampening the closing impact force between vacuum interrupter contacts and, more particularly, to an anti-bounce dampener assembly for dampening the closing impact force between vacuum interrupter contacts, where the dampener assembly includes a moving guide tube and a dampening spring. 
     Discussion of the Related Art 
     An electrical power distribution network, often referred to as an electrical grid, typically includes power generation plants each having power generators, such as gas turbines, nuclear reactors, coal-fired generators, hydro-electric dams, etc. The power plants provide power at a variety of medium voltages that are then stepped up by transformers to a high voltage AC signal to be connected to high voltage transmission lines that deliver electrical power to substations typically located within a community, where the voltage is stepped down to a medium voltage for distribution. The substations provide the medium voltage power to three phase feeders including three single phase feeder lines that carry the same current but are 120° apart in phase. three phase and single phase lateral lines are tapped off of the feeder that provide the medium voltage to various distribution transformers, where the voltage is stepped down to a low voltage and is provided to loads, such as homes, businesses, etc. Power distribution networks of the type referred to above typically include switching devices, breakers, reclosers, interrupters, etc. that control the flow of power throughout the network. 
     Periodically, faults occur in the distribution network as a result of various things, such as animals touching the lines, lightning strikes, tree branches falling on the lines, vehicle collisions with utility poles, etc. Faults may create a short-circuit that increases the stress on the network, which may cause the current flow to significantly increase, for example, many times above the normal current, along the fault path. This amount of current causes the electrical lines to significantly heat up and possibly melt, and also could cause mechanical damage to various components in the network. These faults are often transient or intermittent faults as opposed to a persistent or bolted fault, where the thing that caused the fault is removed a short time after the fault occurs, for example, a lightning strike. In such cases, the distribution network will almost immediately begin operating normally after a brief disconnection from the source of power. 
     A vacuum interrupter is a switch that employs opposing contacts, one fixed and one movable, positioned within a vacuum enclosure. When the vacuum interrupter is opened by moving the movable contact away from the fixed contact to prevent current flow through the interrupter a plasma arc is created between the contacts that is quickly extinguished by the vacuum, where metal vapor is emitted from the contacts. The separated contacts in vacuum provide dielectric strength that exceeds power system voltage and prevents current flow. The vacuum interrupter housing supports the contact structures and is an insulator, typically ceramic, to provide dielectric strength. 
     Fault interrupters, for example, single phase self-powered reclosers that employ vacuum interrupters and magnetic actuators, are provided on utility poles and in underground circuits along a power line and have a switch to allow or prevent power flow downstream of the recloser. These reclosers typically detect the current and/or voltage on the line to monitor current flow and have controls that indicate problems with the network circuit, such as detecting a high current fault event. If such a high fault current is detected the recloser is opened in response thereto, and then after a short delay closed to determine whether the fault is a transient fault. If high fault current flows when the recloser is closed after opening, it is immediately re-opened. If the fault current is detected a second time, or multiple times, during subsequent opening and closing operations indicating a persistent fault, then the recloser remains open, where the time between detection tests may increase after each test. 
     The magnetic actuator used in these types of reclosers typically have an armature or plunger that is moved by an electrical winding wound on a stator to open and close the vacuum interrupter contacts, where the plunger and the stator provide a magnetic path for the magnetic flux produced by the winding, and where the plunger is rigidly fixed to the movable contact by a drive rod. In one design, when the actuator is controlled to close the vacuum interrupter, the winding is energized by current flow in one direction, which causes the plunger to move and seat against a latching plate. The current is then turned off to de-energize the coil and permanent magnets hold the plunger against the latching plate and against a compression force of an opening spring. When the actuator is controlled to open the vacuum interrupter, the winding is energized by current flow in the opposite direction, which breaks the latching force of the permanent magnets and allows the opening spring to open the vacuum interrupter. A compliance spring is provided in addition to the opening spring to provide an additional opening force at the beginning of the opening process so as to break the weld on the interrupter contacts. 
     When the movable contact impacts the fixed contact at high speed during closing of the vacuum interrupter it will often bounce off of the fixed contact for a brief time period, for example two milliseconds, creating a gap therebetween. This contact bounce between the contacts of the vacuum interrupter can cause arcing and welding between the movable and fixed contacts, which results in higher forces required to open the vacuum interrupter, and in extreme cases may prevent opening of the vacuum interrupter contacts completely. Efforts to reduce contact bounce by dampening of the moving contact of the vacuum interrupter is limited by the stiffness of the compliance spring employed in the actuator. 
     SUMMARY 
     The following discussion discloses and describes an anti-bounce dampener assembly for dampening the closing impact force between vacuum interrupter contacts in a vacuum interrupter assembly. The vacuum interrupter assembly includes an outer housing, a contact adapter positioned within an opening in the housing and a vacuum interrupter positioned within the housing, where the vacuum interrupter includes an insulator having a first end and a second end, a first end cap sealed to the first end of the insulator and a second end cap sealed to the second end of the insulator. The vacuum interrupter assembly also includes a fixed contact stem positioned within the vacuum interrupter and including a first shaft coupled to the first end cap and a first contact and a movable contact stem positioned within the vacuum interrupter and including a second shaft connected to the second end cap by a flexible bellows and a second contact. The dampener assembly includes a dampening spring positioned within the contact adapter, a guide tube extending through the contact adapter and the dampening spring, where the guide tube is coupled to the fixed contact stem, and a bolt extending through the guide tube and being rigidly secured to the fixed contact stem. An impact force caused when the second contact impacts the first contact when the vacuum interrupter is closed causes the fixed contact stem, the guide tube, the bolt and the vacuum interrupter to move against the bias of the dampening spring and dampen the impact force. A flexible strap is electrically coupled to the fixed contact stem and the contact adapter, and flexes when the fixed contact stem moves so as to maintain electrical coupling between the fixed contact stem and the contact adapter. 
     Additional features of the disclosure will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is an isometric view of a switch assembly connected to a pole mounted insulator and including a single phase self-powered magnetically actuated switching device; 
         FIG.  2    is a cross-sectional type view of a vacuum interrupter assembly separated from the switching device that includes an anti-bounce dampener assembly for dampening vacuum interrupter contacts; and 
         FIG.  3    is a broken-away view of the vacuum interrupter assembly shown in  FIG.  2   . 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     The following discussion of the embodiments of the disclosure directed to an anti-bounce dampener assembly for dampening the closing impact force between vacuum interrupter contacts is merely exemplary in nature, and is in no way intended to limit the disclosure or its applications or uses. 
       FIG.  1    is an isometric view of a pole mounted switch assembly  10  including a single phase self-powered magnetically actuated switching device  12  intended to represent any switching device suitable for the purposes discussed herein. The switching device  12  is coupled to an upper contact assembly  14  at one end and a mounting hinge  16  at an opposite end. The contact assembly  14  is secured to one end of an insulator  18  having skirts  20  and the mounting hinge  16  is secured to an opposite end of the insulator  18 , where the insulator  18  is mounted to a bracket  24  that may be attached to a utility pole (not shown). The mounting hinge  16  includes a channel catch  28  that accepts a trunnion rod  30  coupled to the device  12  and that is electrically coupled to a unit bottom contact (not shown). The contact assembly  14  includes a top mounting tab  32 , an extension tab  34  and a spring  36  positioned between the tabs  32  and  34 . The contact assembly  14  also includes a support tab  38  bolted to the extension tab  34  by a bolt  40  and a pair of mounting horns  42  coupled to and extending from the support tab  38  opposite to the extension tab  34 . A guiding pull ring member  44  is coupled to a top of the device  12  and allows a worker to easily install and remove the device  12  from the utility pole by pulling on the ring member  44  to disconnect the device  12  from the contact assembly  14 , rotating the device  12  outward on the trunnion rod  30  and then lifting the device  12  out of the catch  28 . 
     The switching device  12  includes a vacuum interrupter assembly  50  having an outer insulation housing  52  that encloses a vacuum interrupter (see  FIGS.  2  and  3   ) of the type referred to above, where the vacuum interrupter assembly  50  is representative of any vacuum interrupter assembly known in the art for medium voltage uses that is suitable for the purposes discussed herein. More particularly, the vacuum interrupter defines a vacuum chamber that encloses a fixed contact that is electrically coupled to a unit top contact  54  and a movable contact that is electrically coupled to the unit bottom contact, where the fixed and movable contacts are in contact with each other within the vacuum chamber when the vacuum interrupter is closed. When the vacuum interrupter is opened by moving the movable contact away from the fixed contact the arc that is created between the contacts is extinguished by the vacuum at a zero current crossing. The switching device  12  also includes an enclosure  56  that encloses a magnetic actuator or other device that opens and closes the vacuum interrupter, various electronics, controllers, energy harvesting devices, sensors, communications devices, etc. consistent with the discussion herein. 
       FIG.  2    is a cross-sectional type view and  FIG.  3    is a broken-away view of the vacuum interrupter assembly  50 . The vacuum interrupter assembly  50  includes an outer insulation housing  62  enclosing a vacuum interrupter  64  having a top metallic end cap  68 , a bottom metallic end cap  70  and a cylindrical ceramic insulator  72  extending between and being sealed to the end caps  68  and  70  to define a vacuum chamber  74 . A top contact adapter  66  is formed to an opening  80  in the housing  62 . A metallic bellows  76  is electrically coupled to the end cap  70  and is positioned within the chamber  74 . A fixed contact stem  78  is brazed and electrically coupled to the end cap  68  and extends through the end cap  68  into the chamber  74 , where the stem  78  includes a shaft portion  84  and a cup portion  86 . Likewise, a movable contact stem  90  electrically connected to, for example, a drive rod (not shown) coupled to an actuator (not shown) is electrically coupled and sealed to the bellows  76  and extends through the bellows  76  into the chamber  74 , where the stem  90  includes a shaft portion  92  and a cup portion  94 , and where the bellows  76  maintains the vacuum within the chamber  74  when the stem  90  moves. An arcing contact  98  is electrically secured to the cup portion  86  and an arcing contact  100  is electrically secured to the cup portion  94  so that a gap  102  is defined therebetween when the vacuum interrupter  64  is open, as shown. A viscous high dielectric insulation medium  118  is provided around the vacuum interrupter  64  to provide dielectric strength. When the vacuum interrupter  64  is closed, the contacts  98  and  100  are held in contact with each other under spring bias (not shown) and when the vacuum interrupter  64  is opened, the stem  90  moves the contact  100  away from the contact  98 , thus creating a plasma arc that is interrupted at the next zero current crossing due to the current interrupting capability of the vacuum. 
     The vacuum interrupter assembly  50  also includes an anti-bounce dampener assembly  120  for dampening and reducing the contact bounce between the contacts  98  and  100  when the vacuum interrupter  64  is closed. The dampener assembly  120  includes a moving metal guide tube  122  positioned within a bore  124  extending through the contact adapter  66 . The dampener assembly  120  also includes a flexible conductive strap  126  having one end positioned between the guide tube  122  and the shaft portion  84  of the stem  78  and an opposite end positioned between the housing  62  and the adapter  66  so as to provide a current path between the stem  78  and the adapter  66 . A preloaded dampener spring  130  is positioned within a bore  132  in the adapter  66  and is pressed against the end of the strap  126  in contact with the stem  78 . A mounting bolt  134  extends through the guide tube  122 , the spring  130  and the strap  126  and is threaded into the shaft portion  84  of the stem  78  to secure the assembly  120  together. A sealing cup  136  prevents the insulation medium  118  from getting into the dampener assembly  120 . 
     When the vacuum interrupter  64  closes and the contact  100  impacts the contact  98 , the stem  78  is forced upward against the bias of the spring  130 , which causes the guide tube  122  and the mounting bolt  134  to move in the adapter  66 . Since the stem  78  is rigidly fixed to the end cap  68 , the entire vacuum interrupter  64  also moves upward against the bias of the spring  130 , where this movement of the vacuum interrupter  64  is then stabilized by the spring  130 . Particularly, the dampening spring&#39;s pre-load force has adequate margin over the highest compliance spring force in order to provide a stable fixed position prior to and after impact deflection. Thus, the movement of the mass of the vacuum interrupter  64  and associated components when the contact  100  impacts the contact  98  reduces or dampens the bounce of the contact  100  off of the contact  98 . Additionally, when the vacuum interrupter  64  moves, a shear force is created in the insulation medium  118 , which also operates to dampen the impact between the contacts  98  and  100 . 
     The foregoing discussion discloses and describes merely exemplary embodiments of the present disclosure. One skilled in the art will readily recognize from such discussion and from the accompanying drawings and claims that various changes, modifications and variations can be made therein without departing from the spirit and scope of the disclosure as defined in the following claims.