Patent Application
20230141161
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.
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.
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.
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.
The switching device 12 includes a vacuum interrupter assembly 50 having an outer insulation housing 52 that encloses a vacuum interrupter (see
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'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.
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.
| Number | Date | Country | |
|---|---|---|---|
| 63278217 | Nov 2021 | US |
