Patent Application
20060148292
The present invention relates generally to the field of loadbreak switching. More particularly, this invention relates to enhancements in separable insulated connectors for reducing the probability of flashover during loadbreak switching.
Separable insulated connectors provide the interconnection between energy sources and energy distribution systems. Typically, energy distribution is made possible through a large power distribution system, which results in power distribution to homes, businesses, and industrial settings throughout a particular region. In most cases, the distribution of power begins at a power generation facility, such as a power plant. As the power leaves the power plant, it enters a transmission substation to be converted up to extremely high voltages for long-distance transmission, typically in the range of 150 kV to 750 kV. Then, power is transmitted over high-voltage transmission lines and is later converted down to distribution voltages that will allow the power to be distributed over short distances more economically. The power is then reduced from the 7,200 volts typically delivered over a distribution bus to the 240 volts necessary for ordinary residential or commercial electrical service.
Separable insulated connectors typically consist of a male connector and a female connector. The mating of the male and female connectors are necessary to close the electrical circuit for distribution of power to customers. The female connector is typically a shielding cap or an elbow connector that mates with a male connector. The male connector is generally a loadbreak bushing that typically has a first end adapted for receiving a female connector (e.g., an elbow connector or shielding cap) and a second end adapted for connecting to a conductive stud. The first end of the male connector is an elongated cylindrical member with a flange on the rim of the member. The flange typically provides an interference fit between the bushing and the mating elbow connector. The flange secures the bushing to a groove in the inner wall of the mating elbow connector. The interference fit and the flange-groove mechanism are typical mating methods for a male and female connector.
Positioned within the male and female connectors are female and male contacts, respectively. The male contact is typically an electrode probe. The female contact is typically a contact tube that mates with the electrode probe from the female connector. When the male and female contacts mate, the electrical circuit is closed.
The process of separating these energized, electrical connectors is referred to as loadbreak switching. Since one or both connectors are energized during loadbreak, there exists a possibility of a flashover occurring. A flashover occurs when the electrical arc generated by an energized connector extends to a nearby ground point, which is undesirable. Particularly, for example, when a line-crew operator separates the male and female connectors in a loadbreak operation too slowly, the operator can drag the electrical arc out of the bushing. When the arc is dragged out of the male connector, the arc may flash over and seek a nearby ground point. Such an occurrence is undesirable and should be avoided.
During a switching operation, flashover may be caused at least in part by air pressure and conductive particles that build up within the electrical connectors. In order to equalize the pressure and gas within the connectors, a venting path is created to release the air pressure and gases during loadbreak switching. Typically, the venting path consists of a gap between an internal insulative layer within the bushing and the female contact. As the electrical connectors are separated and, as a result, the gases are released, the gases eject small fragments of conductive material (i.e., mainly copper and carbon) from within the bushing back toward the electrode probe. Since the fragments of copper and carbon are conductive, they can easily form a conductive path, resulting in a flashover induced by the gas dissipation.
Accordingly, it should be advantageous to develop a loadbreak connector that exhibits a reduced probability of flashover. It would be desirable to provide a separable insulated connector or the like of a type disclosed in the present application that includes any one or more of these or other advantageous features. It should be appreciated, however, that the teachings herein may also be applied to achieve devices and methods that do not necessarily achieve any of the foregoing advantages but rather achieve different advantages.
One embodiment pertains to redirecting the gases and conductive particles through a venting path away from the mating male contact. A separable insulated connector, in accordance with one embodiment of the present invention, comprises a connector body with a venting path formed therein for venting gases and particles during a loadbreak operation. The terminal portion of the venting path diverts gases and particles away from the axis of motion of the male contact.
Still other advantages of the present invention will become readily apparent to those skilled in this art from review of the enclosed description, wherein the preferred embodiment of the invention is disclosed, simply by way of the best mode contemplated, of carrying out the invention. As it shall be understood, the invention is capable of other and different embodiments, and its several details are capable of modifications in various respects, all without departing from the invention. Accordingly, the figures and description shall be regarded as illustrative in nature, and not as restrictive.
Referring to
Referring now to
The middle section of insulated housing 3, typically referred to as semi-conductive shield 5, is positioned between the first end and second end and is cylindrically larger than the first and second end. The middle section preferably comprises a semi-conductive material that provides a deadfront safety shield. Positioned within the bore of insulated housing 3 is an internal conductive layer 7 layered close to the inner wall of insulated housing 3. Internal conductive layer 7 preferably extends from near both ends of insulated housing 3 to facilitate optimal electrical shielding. Positioned within internal conductive layer 7 is internal insulative layer 9, which provides insulative protection for conductive layer 7 from a ground plane or electrode probe 21. Contact tube 11 is preferably a cylindrical member, which is capable of passing an electrode probe 21 from elbow connector 29. Contact tube 11 is slidably movable from a first position to a second position. In the first position, contact tube 11 is retracted into insulated housing 3, and in the second position, contact tube 11 extends substantially beyond the rim of the insulated housing 3 for receiving an electrode probe 21 during a fault closure. Contact tube 11 preferably comprises an arc-ablative component, which produces an arc extinguishing gas during loadbreak switching for enhanced switching performance.
The movement of contact tube 11 from the first to the second position is assisted by piston contact 13, which is affixed to contact tube 11. Piston contact 13 typically comprises copper or a copper alloy and has a knurled base with vents, providing an outlet for gases and conductive particles to escape which may be generated during loadbreak switching. Piston contact 13 also provides a reliable, multipoint current interchange to contact holder 19. Contact holder 19 is typically a copper component, positioned adjacent to conductive layer 7 and piston contact 13, for transferring current from piston contact 13 to a conductive stud, although contact holder 19 and conductive layer 7 may be integrally formed as a single unit. Contact tube 11 will typically be in its retracted position during continuous operation of bushing 1. During a fault closure, piston contact 13 slidably moves contact tube 11 to an extended position where it can mate with the electrode probe 21, thus reducing the likelihood of a flashover.
Positioned within contact tube 11 are a plurality of finger contacts 17. Finger contacts 17 are threaded into the base of piston contact 13, for providing a current path between electrode probe 21 and contact holder 19. As elbow connector 29 is mated with a bushing 1, electrode probe 21 passes through contact tube 11, in order to connect with finger contacts 17 for continuous current flow. Finger contacts 17 provide multi-point current transfer to a conductive stud. Additionally, bushing 1 has threaded base 15 for connection to a conductive stud. Threaded base 15 is positioned near the extremity of the second end of insulated housing 3, adjacent to hex broach 25. Hex broach 25 is preferably a six-sided aperture, which assists in the installation of a bushing 1 onto a conductive stud with a torque tool. Hex broach 25 is advantageous because it allows the bushing 1 to be tightened to a desired torque.
A venting path is created, such that the gases and conductive particles exit the hollow area of contact tube 11 and travel between the outer surface of contact tube 11 and internal insulative layer 9 to escape from the first end of insulated housing 3. As shown in
Throughout the specification, numerous advantages of exemplary embodiments have been identified. It will be understood of course that it is possible to employ the teachings herein so as to without necessarily achieving the same advantages. Additionally, although many features have been described in the context of a power distribution system comprising multiple cables and connectors linked together, it will be appreciated that such features could also be implemented in the context of other hardware configurations. Further, although certain methods are described as a series of steps which are performed sequentially, the steps generally need not be performed in any particular order. Additionally, some steps shown may be performed repetitively with particular ones of the steps being performed more frequently than others, when applicable. Alternatively, it may be desirable in some situations to perform steps in a different order than described.
Many other changes and modifications may be made to the present invention departing from the spirit thereof.
