Patent Application
20230145762
This disclosure relates generally to a tamper resistant plug and, more particularly, to a tamper resistant plug for a hermetically sealed tank associated with medium-voltage switchgear, where the plug includes a polygon shaped interface surface with only rounded edges.
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 feeders 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. Some power distribution networks may employ a number of underground single-phase lateral circuits that feed residential and commercial customers. Often times these circuits are configured in a loop and fed from power sources at both ends, where an open circuit location in the loop isolates the two power sources.
Power distribution networks of the type referred to above typically include a number of switching devices, breakers, reclosers, current interrupters, etc. that control the flow of power throughout the network. Standalone pad mounted and underground switchgear including electrical disconnect switches, fuses and/or circuit breakers used to control, protect and isolate electrical equipment are often employed to de-energize equipment to allow work to be done and to clear faults. Switchgear often include load-interrupter switches, resettable, vacuum fault interrupters and other equipment that are enclosed in a hermetically sealed and gas-insulated steel tank to provide electrical isolation. The tank is generally filled with a blend of CO2 and 3M™ Novec™ 4710 insulating gas (CO2-Novec) through a fill port, and the fill port is subsequently sealed with a plug, where the plug is designed to be opened with a special tool. However, the plug in existing switchgear tanks can generally be opened with a flat head screwdriver or other commonly available tool. Even though these tanks are hermetically sealed at the factory, they can leak over time, which would lead the owner of the switchgear to remove the plug using these tools and refill the tank, possibly with the wrong insulating gas, such as SF6.
Hermetically sealed gas-insulated equipment (GIE) can be defined under regulations as being pre-charged with covered insulating gas, sealed at the factory and designed by the manufacturer to not be fillable by the GIE owner or a third-party designee. In order to meet this definition of hermetically sealed GIE, the plug for these tanks needs to be redesigned such that it is not able to be removed by the equipment owner or a third-party designee and filled with insulating gas.
The following discussion discloses and describes a tamper resistant plug that has particular application for sealing a fill port in a hermetically sealed and gas-insulated tank associated with medium-voltage switchgear. The plug includes a body portion and a top annular rim defining a central recess and having an internal surface facing the recess, where the internal surface has a polygon shape with only rounded edges. In one embodiment, the polygon shape is a trilobe.
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 a tamper resistant plug is merely exemplary in nature, and is in no way intended to limit the disclosure or its applications or uses. For example, the tamper resistant plug has particular application for sealing a fill port of a hermetically sealed and gas-insulated tank in medium-voltage switchgear. However, as will appreciated by those skilled in the art, the plug may have application for sealing other enclosures.
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. 63/278,215, filed on Nov. 11, 2021, the disclosure of which is hereby expressly incorporated herein by reference for all purposes.
| Number | Date | Country | |
|---|---|---|---|
| 63278215 | Nov 2021 | US |
