Patent Application
20240120164
This disclosure relates generally to an actuation assembly that is part of and operates to open and close a switching device and, more particularly, to an actuation assembly that is part of and operates to open and close a cut-out mounted switching device.
An electrical power distribution network, often referred to as an electrical grid, typically includes a number of power generation plants each having a number of 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 a number of 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 a number of three phase feeders including three single phase feeder lines that carry the same current, but are 120° apart in phase. A number of 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 a number of loads, such as homes, businesses, etc. Power distribution networks of the type referred to above typically include a number of 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.
Traditionally, a fuse is employed as a primary overload protection device for protecting distribution transformers and other devices that has a certain rating so that the fuse will operate above a transformer inrush current, but below a transformer through fault protection withstand or damage curve. However, fuses often create an arc when they operate, which has obvious dangers and drawbacks. It has become increasingly popular to replace the traditional fuse with a cutout-mounted fault interrupting device that employs a vacuum interrupter and a magnetic actuator to operate the vacuum interrupter. 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 operating the magnetic actuator to move 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 contained and quickly extinguished by the vacuum at the next zero current crossing. When fault current is detected by the device the vacuum interrupter is opened and the device is released or “drops out” from its mounting indicating that it has operated.
The dropout feature of a cut-out mounted vacuum interrupting device requires a magnetic actuator to initiate the dropout operation, which adds significant cost to the device. After a dropout operation the device needs to be reset by closing the vacuum interrupter and charging opening and compliance springs in the magnetic actuator. One known device resets by tripping the device closed just after the dropout operation. Another known device resets by harvesting energy with a high voltage resistor assembly and automatically closing the magnetic actuator when the device replaced into the mounting. Both of these techniques require storing enough electrical energy in a large capacitor to close the vacuum interrupter and reset the device.
The following discussion discloses and describes an actuation assembly that is part of and operates to open and close a switching device. The switching device includes a switch coupled to a first coupling assembly and the actuation assembly through a drive linkage, where the actuation assembly is rotatably coupled to a second coupling assembly. The actuation assembly includes an actuator, opposing plates defining a space therebetween and being coupled to the actuator, and a dropout lever rigidly coupled to the second coupling assembly and positioned between the opposing plates. The dropout lever includes opposing dropout arms defining a space therebetween, a first cam coupled to one of the dropout arms in the space and a second cam coupled to the other dropout arm in the space. A drive rod is coupled to the drive linkage and the actuator that extends between the first and second cams, where the drive rod includes a flange. A release lever is pivotally coupled to the opposing side plates and engages the flange. A latching lever is pivotally coupled to one of the dropout arms opposite to the second coupling assembly at one end. A trip link including a slot is rigidly coupled to the release lever at one end, where an end of the latching lever opposite to the dropout arm is slidable in the slot. A spring link is coupled to the release lever at one end and one end of a spring at an opposite end, where the spring is coupled to one of the plates at an opposite end. Actuation of the actuator to open the switch causes the drive rod with the flange to move, which causes the release lever to rotate under bias of the spring, which pulls on the trip link and causes the latching lever to slide in the slot and causes ends of the dropout arms opposite to the second coupling assembly to be pulled, which disengages the switch from the first coupling assembly and allows the switch to rotate on the second coupling assembly. A compliance stop is secured to the drive rod and the second coupling assembly includes a rotation stop. Drop out and rotation of the switch eventually causes the dropout lever to engage the rotation stop, but allows the switch to continue rotating, which causes the compliance stop to engage the first and second cams, which causes the release lever, the trip link, the latching lever and the dropout arms to return to the switch closed position.
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 actuation assembly that is part of and operates to open and close a switching device 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 50 having an outer insulation housing 52, where the vacuum interrupter 50 is representative of any vacuum interrupter known in the art for medium voltage uses that is suitable for the purposes discussed herein. The vacuum interrupter 50 includes a vacuum chamber that encloses a fixed contact that is electrically coupled to the unit top contact 48 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 50 is closed. When the vacuum interrupter 50 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 actuation assembly 60 that is coupled to the vacuum interrupter 50 by a drive linkage 62 and having a magnetic actuator 64. A compliance spring 68 sitting on a compliance spring stop 58 holds the vacuum interrupter contacts closed during operation.
As will be discussed in detail below, operation or opening of the vacuum interrupter 50 in response to fault current automatically causes the contact 48 to be released from the upper assembly 14 so that the switching device 12 rotates on the rod 28 under the force of gravity to a dropout position. As the switching device 12 is rotating on the rod 28, the vacuum interrupter 50 is automatically closed and ready to be reconnected to the upper assembly 14.
The actuation assembly 60 includes opposing side plates 70 and 72 mounted to a support plate 74 through which a drive rod 76 coupled to the drive linkage 62 extends. A U-shaped dropout lever 80 having opposing arms 82 and 84 is coupled to the trunnion 46 and is pivotable on a pivot pin 86 secured to the side plates 70 and 72. A flange 90 is provided on the drive rod 76 and a pair of dropout lever cams 92 and 94 are coupled to the arms 82 and 84, respectively, and are close to or in contact with the drive rod 76. A release lever 96 is pivotally mounted to the side plates 70 and 72 and engages the flange 90. A pair of latching levers 100 and 102 are pivotally coupled to a rod 104 secured to the arms 82 and 84 opposite to the trunnion 46, where a spring 106 is wound around the rod 104. The latching levers 100 and 102 are in a toggle state when the vacuum interrupter 50 is in the closed position. A trip link 110 including a slot 114 is coupled to the release lever 96 at one end and a rod 116 at an opposite end, where the latching levers 100 and 102 are also coupled to the rod 116 opposite the rod 104. A spring link 120 is coupled to a pin 122 on the release lever 96 outside of the side plate 70 at one end and an end piece 124 of a spring dampener 126 at an opposite end, where the dampener 126 supports a spring 128 positioned between the end piece 124 and a tab 130 secured to the side plate 70.
During operation, the unit top contact 48 is engaged with the upper assembly 14 and the components in the actuation assembly 60 are configured as shown in
When the trunnion assembly 30 is rotating on the pivot rod 28 a trunnion stop 142 on the trunnion assembly 30 will eventually engage a hinge stop 144 on the cutout hinge 26, which stops the trunnion 46 and thus the drop out lever 80 from further rotation. However, because the switching device 12 is secured to the trunnion 46 through the pivot pin 86, the moving mass of the switching device 12 causes it to continue rotating. As the drive rod 76 continues to move relative to the dropout lever 80, the compliance spring stop 58 will eventually be driven into the cams 92 and 94. This causes the drive rod 76 to be driven towards the vacuum interrupter closed position, previously upward, but sideways now because the switching device 12 has dropped out, against the bias of the opening spring 140. When the vacuum interrupter contacts engage each other, the permanent magnets latch the vacuum interrupter 50 in the closed position, where the opening spring 140 and the compliance spring 68 are now in the charged position. Further, the release lever 96 is rotated in a counter-clockwise direction, the latching levers 100 and 102 are returned to the toggle state and the spring 126 is charged. The switching device 12 can then be re-engaged with the upper assembly 14 using the ring 44.
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. 63/415,186, filed on Oct. 11, 2022, the disclosure of which is hereby expressly incorporated herein by reference for all purposes.
| Number | Date | Country | |
|---|---|---|---|
| 63415186 | Oct 2022 | US |
