Patent Application
20210075212
The present disclosure relates generally to a fault protection system for providing protection from fault current for components and devices on a lateral line in a power distribution network and, more particularly, to a fault protection system for providing protection from fault current for components and devices on a lateral line proximate a distribution transformer.
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 90° apart in phase. A number of lateral lines are tapped off of one of the single-phase feeder lines 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.
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 current on the network to be several times above the normal current along the fault path. This amount of current could cause the electrical lines to significantly heat up and possibly melt, and also could cause mechanical damage to various components in the substation and in the network.
A power distribution network of the type referred to above typically employ one or more fuses positioned along each lateral line, for example, proximate to a tap location where the lateral line is connected to the feeder and on a distribution line tapped off of the lateral line. A fuse is an independent electrical device that is not in communication with other components or devices in the network, where the fuse creates an open circuit if an element within the fuse heats up above a predetermined temperature as a result of high fault current so as to prevent short-circuit faults on the lateral line from affecting other parts of the network, and thus, the fuse is a single shot device.
Better fault control could be provided if the fuse was replaced with a smart switching device, such as a single-phase recloser, that is able to measure voltage and current, communicate with other devices, open a switch in response to fault current and provide other recloser operations. Thus, personnel would not need to be dispatched to replace the fuse if it is operated. Smart switching devices for this purpose are known in the art, but are expensive, thus making it economically unfeasible to replace the many fuses in the network with such devices. For example, known smart switching devices of this type require their own power supply, such as a current transformer or a voltage transformer sometimes in combination with a battery pack, that is necessary to power the electronics and sensors that measure the current and voltage. However, these power sources are a major part of the expense of the smart device.
The following discussion discloses and describes a fault protection system for providing protection from fault current for components and devices on a lateral line proximate a distribution transformer in a power distribution network. The system includes a single-phase recloser having a vacuum interrupter or other switching device that is controlled by a controller. In one embodiment, the recloser has an insulating body that is molded in combination with an insulating body of a bushing that is connected to the distribution transformer. In this embodiment, the controller is powered by a current transformer within the recloser, although other techniques can be provided for powering the recloser because of its proximity to a frame of the transformer, such as using capacitive current. In another embodiment, the recloser is mounted to a utility pole separate from the distribution transformer, where the controller is powered by the low voltage side of the distribution transformer and the current transformer is eliminated. An isolated power supply is provided between the transformer and the controller to provide voltage isolation.
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 fault protection system for providing protection from fault current for components and devices on a lateral line proximate a distribution transformer in a power distribution network, where the protection system includes a single-phase recloser molded to a bushing coupled to the transformer or a single-phase recloser having a controller that is powered by the transformer is merely exemplary in nature, and is in no way intended to limit the invention or its applications or uses.
The switching device 12 includes an upper insulating housing 40 and a lower insulating housing 42. A vacuum interrupter 44 is provided in the upper housing 40 and is coupled to an actuator 46, such as a solenoid, in the lower housing 42 by a coupler 50. The actuator 46 is controlled by a controller 52 also located in the lower housing 42 to cause the actuator 46 to open and close the vacuum interrupter 44 to prevent or allow current flow to the transformer 14 for fault protection in a manner well understood by those skilled art. The switching device 12 also includes sensors 54 for measuring the current, where the controller 52 processes the measurement signals and controls the position of the vacuum interrupter 44, and a transceiver 56 for transmitting data and messages to a control facility (not shown) and/or to other switch devices, reclosers and components. When the vacuum interrupter 44 is closed current is provided on line 60 to a current transformer 62 that harvests power therefrom and provides power to the controller 52 on line 64. The operation of the switching device 12 as described so far is well understood by those skilled in the art.
The transformer 14 includes a bushing 70 having an internal conductor 72 and an outer insulation body 74, where the bushing 70 can be made of any suitable material, such as porcelain, and where the internal conductor 72 is electrically coupled to the high voltage coil (not shown) in the transformer 14. The bushing 70 is a known part of a distribution transformer, but in this embodiment it is also used to secure the switching device 12 to the transformer 14, where the length of the bushing 70 may need to be extended beyond known designs. Particularly, a top end 74 of the bushing 70 is molded into the lower housing 42 and a bottom end 76 is secured to the can 16. Therefore, the bushing 70 and the switching device 12 can be manufactured as a single unit and then attached to the transformer 14. In another embodiment, instead of the switching device 12 being mounted to the top end 74 of the bushing 70, the switch device 12 can be completely molded inside of the bushing 70, thus saving further cost and reducing space constraints. In the known designs, the switching device 12 would not be used and would be replaced by a fuse that would be connected to the bushing 70 by an electrical line.
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.
| Number | Date | Country | |
|---|---|---|---|
| 62896602 | Sep 2019 | US |
