Patent Application
20080160809
The invention relates generally to cable connectors for electric power systems, and more particularly to separable insulated loadbreak connector systems for use with cable distribution systems.
Electrical power is typically transmitted from substations through cables which interconnect other cables and electrical apparatus in a power distribution network. The cables are typically terminated on bushings that may pass through walls of metal encased equipment such as capacitors, transformers or switchgear.
Separable loadbreak connectors allow connection or disconnection of the cables to the electrical apparatus for service, repair, or expansion of an electrical distribution system. Such connectors typically include a contact tube surrounded by elastomeric insulation and a semiconductive ground shield. A contact piston is located in the contact tube, and a female contact having contact fingers is coupled to the piston. An arc interrupter, gas trap and arc-shield are also mounted to the contact tube. The female contact fingers are matably engaged with an energized male contact of a mating bushing, typically an elbow connector, to connect or disconnect the power cables from the apparatus. The piston is movable within the contact tube to hasten the closure of the male and female contacts and thus extinguish any arc created as they are engaged.
Such connectors are operable in “loadmake”, “loadbreak”, and “fault closure” conditions. Fault closure involves the joinder of male and female contact elements, one energized and the other engaged with a load having a fault, such as a short circuit condition. In fault closure conditions, a substantial arcing occurs between the male and female contact elements as they approach one another and until they are joined in mechanical and electrical engagement. Considerably more arc-quenching gas and mechanical assistance are required to extinguish the arc in a fault closure condition than in loadmake and loadbreak conditions, and it is known to use an arc-quenching gas to assist in accelerating the male and female contact elements into engagement, thus minimizing arcing time. A rigid piston stop is typically provided in the contact tube to limit movement of the piston as it is driven forward during fault closure conditions toward the mating contact.
It has been observed, however, that considerable force can be generated when the piston engages the piston stop, and in certain cases the force can be sufficient to dislodge the female finger contacts from the contact tube, leading to a fault close failure and sustained arcing conditions and hazard. Additionally, proper closure of the connector is dependent upon the proper installation and position of the piston stop, both of which are subject to human error in the assembly and/or installation of the connector, and both of which may result in fault closure failure and hazardous conditions. It would be desirable to avoid these and other reliability issues in existing separable interface connectors.
According to an exemplary embodiment, a separable loadbreak connector is provided. The connector comprises a contact tube having an axial passage therethrough, and a contact member slidably mounted within the axial passage and movable therein during a fault closure condition. The contact member is axially movable within the passage with the assistance of an arc quenching gas during the fault closure condition, and a shock absorbent stop element is mounted to the contact tube and limiting movement of the contact member in the fault closure condition.
According to another exemplary embodiment, a separable loadbreak connector for making or breaking an energized connection in a power distribution network is provided. The connector comprises a conductive contact tube having an axial passage therethrough, an elastomeric insulation surrounding the contact tube, a conductive piston disposed within the passage and displaceable therein with the assistance of an arc quenching gas, a female contact member mounted stationary to the piston, and a shock absorbent stop ring element within the axial passage and restricting displacement of the piston.
According to another exemplary embodiment, a separable loadbreak connector to make or break a medium voltage connection with a male contact of a mating connector in a power distribution network is provided. The separable loadbreak connector comprises a conductive contact tube having an axial passage therethrough, an elastomeric insulation surrounding the contact tube, a conductive piston disposed within the passage and displaceable therein with the assistance of an arc quenching gas, a loadbreak female contact member mounted stationary to the piston, an arc interrupter adjacent the female contact member and movable therewith, and a nonconductive nosepiece coupled to the contact tube and including an integrally formed stop ring at one end thereof. The stop ring limits movement of the piston relative to the contact tube in a fault closure condition.
. According to another exemplary embodiment, a separable loadbreak connector comprises passage means for defining an axial contact passage and loadbreak means, located within the axial contact passage, for making or breaking an energized electrical connection in a power distribution network. Positioning means are provided, coupled to the loadbreak means, for axially displacing the loadbreak means within the contact passage. Assistance means are provided, coupled to the positioning means, for displacing the positioning means during a fault closure condition. As arc interrupter means is provided, adjacent the loadbreak means and movable therewith, for quenching an electrical arc during loadmake and loadbreak conditions, and stop means are connected to the passage means for absorbing impact of the positioning means when the positioning means is displaced within the passage by a predetermined amount.
According to another exemplary embodiment, a separable loadbreak connector system to make or break a medium voltage energized connection in a power distribution network is provided. The system comprises a male connector having a male contact, and a female loadbreak connector. The female connector comprises a conductive contact tube having an axial passage therethrough, an elastomeric insulation surrounding the contact tube, a conductive piston disposed within the passage, and a loadbreak female contact member mounted stationary to the piston and configured to receive the male contact when the male and female connectors are mated. The female contact member and the piston is axially displaceable within the contact passage within the contact passage toward the male contact due to accumulated pressure of an arc quenching gas when the male and female connectors are mated to one another in a fault closure condition. An arc interrupter is adjacent the female contact member and movable therewith, and a shock absorbent stop element is configured to absorb impact of the piston during the fault closure condition and substantially prevent displacement of the piston beyond a predetermined distance within the contact tube.
As shown in
While the male connector 102 is illustrated as an elbow connector in
In an exemplary embodiment, and as shown in
The female connector 104 may be a bushing insert composed of a shield assembly 130 having an elongated body including an inner rigid, metallic, electrically conductive sleeve or contact tube 132 having a non-conductive nose piece 134 secured to one end of the contact tube 132, and elastomeric insulating material 136 surrounding and bonded to the outer surface of the contact tube 132 and a portion of the nose piece 134. The female connector 104 may be electrically and mechanically mounted to a bushing well (not shown) disposed on the enclosure of a transformer or other electrical equipment.
A contact assembly including a female contact 138 having deflectable contact fingers 140 is positioned within the contact tube 132, and an arc interrupter 142 is provided proximate the female contact 138.
The male and female connectors 102, 104 are operable or matable during “loadmake”, “loadbreak”, and “fault closure” conditions. Loadmake conditions occur when the one of the contact elements, such as the male contact element 114 is energized and the other of the contact elements, such as the female contact element 138 is engaged with a normal load. An arc of moderate intensity is struck between the contact elements 114, 138 as they approach one another and until joinder under loadmake conditions. Loadbreak conditions occur when the mated male and female contact elements 114, 138 are separated when energized and supplying power to a normal load. Moderate intensity arcing again occurs between the contact elements 114, 138 from the point of separation thereof until they are somewhat removed from one another. Fault closure conditions occur when the male and female contact elements 114, 138 are mated with one of the contacts being energized and the other being engaged with a load having a fault, such as a short circuit condition. Substantial arcing occurs between the contact elements 114, 138 in fault closure conditions as the contact elements approach one another they are joined. In accordance with known connectors, arc-quenching gas is employed to accelerate the female contact 138 in the direction of the male contact element 140 as the connectors 102, 104 are engaged, thus minimizing arcing time and hazardous conditions.
A contact assembly includes a piston 158 and a female contact element 160 having deflectable contact fingers 162 is positioned within the contact tube 152 and an arc interrupter 164 provided proximate the female contact 160. The piston 158, the female contact element 160, and the arc interrupter 164 are movable or displaceable along a longitudinal axis of the connector 150 in the direction of arrow A toward the male contact element 114 (
The connector 200, may be, for example, a bushing insert or connector connected to an electrical apparatus such as a capacitor, a transformer, or switchgear for connection to the power distribution network. In an exemplary embodiment, the connector 200 includes a conductive contact tube 202, a non-conductive nose piece 204 secured to one end of the contact tube 202, and elastomeric insulating material 206, such as EPDM rubber, surrounding and bonded to the outer surface of the contact tube 202 and a portion of the nose piece 204. A semiconductive ground shield 208 extends over a portion of the insulation 206.
In one embodiment, the contact tube 202 may be generally cylindrical and may have a central bore or passage 209 extending axially therethrough. The contact tube 202 has an inner end 210 with a reduced inner diameter, and the end 210 may be threaded for connection to a stud of a bushing well (not shown) of an electrical apparatus in a known manner. An open outer end 212 of the contact tube 202 includes an inwardly directed annular latching shoulder or groove 214 that receives and retains a latching flange 216 of the nosepiece 204.
In one embodiment, the conductive contact tube 202 acts as an equal potential shield around a contact assembly 220 disposed within the passage 209 of the tube 202. The equal potential shield prevents stress of the air within the tube 202 and prevents air gaps from forming around the contact assembly 220, thereby preventing breakdown of air within the tube during normal operation. While a conductive contact tube 202 is believed to be advantageous, it is recognized that in other embodiments a non-conductive contact tube may be employed that defines a passage for contact elements.
The contact assembly 220 may include a conductive piston 222, a female contact 224, a tubular arc snuffer housing 226, and an arc-quenching, gas-generating arc snuffer or interrupter 228. The contact assembly 220 is disposed within the passage 209 of the contact tube 202. The piston 222 is generally cylindrical or tubular in an exemplary embodiment and conforms to the generally cylindrical shape of the internal passage 209.
The piston 222 includes an axial bore and is internally threaded to engage external threads of a bottom portion 228 of the female contact 224 and fixedly mount or secure the female contact 224 to the piston 222 in a stationary manner. The piston 222 may be knurled at around its outer circumferential surface to provide a frictional, biting engagement with the contact tube 202 to ensure electrical contact therebetween to provide resistance to movement until a sufficient arc quenching gas pressure is achieved in a fault closure condition. Once sufficient arc quenching gas pressure is realized, the piston is positionable or slidable within the passage 209 of the contact tube 202 to axially displace the contact assembly 220 in the direction of arrow B to a fault closure position as shown in
The female contact 224 is a generally cylindrical loadbreak contact element in an exemplary embodiment and may include a plurality of axially projecting contact fingers 230 extending therefrom. The contact fingers 230 may be formed by providing a plurality of slots 232 azimuthally spaced around an end of the female contact 224. The contact fingers 230 are deflectable outwardly when engaged to the male contact element 114 (
The arc snuffer 228 in an exemplary embodiment is generally cylindrical and constructed in a known manner. The arc snuffer housing 226 is fabricated from a nonconductive or insulative material, such as plastic, and the arc snuffer housing 226 may be molded around the arc snuffer 228. As those in the art will appreciate, the arc interrupter 228 generates de-ionizing arc quenching gas within the passage 209, the pressure buildup of which overcomes the resistance to movement of the piston 222 and causes the contact assembly 220 to accelerate, in the direction of arrow B, toward the open end 212 of the contact tube 202 to more quickly engage the female contact element 224 with the male contact element 114 (
In an exemplary embodiment, the arc snuffer housing 226 includes internal threads at an inner end 232 thereof that engage external threads of the female contact 224 adjacent the piston 222. In securing the arc snuffer housing 226 to female contact 224, the arc interrupter 228 and female contact 224 move as a unit within the passage 209 of the contact tube 202.
The nose piece 204 is fabricated from a nonconductive material and may be generally tubular or cylindrical in an exemplary embodiment. The nose piece 204 is fitted onto the open end 212 of the contact tube 202, and extends in contact with the inner surface of the contact tube 202. An external rib or flange 216 is fitted within the annular groove 214 of the contact tube 202, thereby securely retaining the nose piece to 204 to the contact tube 202.
A stop element in the form of a stop ring 240 is integrally formed with the nose piece 204 at one end 242 thereof, and may be tapered at the end 242 as shown in
The stop ring 240, together with the remainder of the nose piece 204, may be fabricated from a non-rigid, compressible, or shock absorbing material that absorbs impact forces when the piston 222 strikes the stop ring 240, while limiting or restricting movement of the piston 222 beyond a predetermined or specified position within the contact tube 202. In other words, the stop ring 240 will prevent movement of the piston 222 relative to the contact tube 202 beyond the general location of the stop ring 240. With the shock absorbing stop ring 240, impact forces of the piston 222 are substantially isolated and absorbed within the stop ring 240, unlike known connectors having rigid piston stops that distribute impact forces to the remainder of the assembly, and specifically to the contact tube. By absorbing the piston impact with the stop ring 240, it is much less likely that impact forces will separate the female contact 224 and the contact fingers 230 from the contact tube, thereby avoiding associated fault closure failure.
Alternatively, the piston impact with the stop ring 240 may be absorbed by shearing of the nose piece 204, either wholly or partially, from the contact tube 202, such as at the interface of the noise piece flanges 216 and the annular groove 214 of the contact tube. The shearing of the nose piece material absorbs impact forces and energy when the piston 222 strikes the stop ring 240, and the resilient insulating material 206 may stretch to hold the nose piece 204 and the contact tube 202 together, further absorbing kinetic energy and impact forces as the piston 222 is brought to a stop. Potential tearing of the insulating material 206 may further dissipate impact forces and energy. Weak points or areas of reduced cross sectional area could be provided to facilitate shearing and tearing of the materials of predetermined locations in the assembly.
Still further, the piston impact with the stop ring 240 may be broken, cracked, shattered, collapsed, crushed or otherwise deformed within the contact tube 202 to absorb impact forces and energy.
It is understood that one or more the foregoing shock absorbent features may utilized simultaneously to bring the piston 222 to a halt during fault closure conditions. That is, shock absorption may be achieved with combinations of compressible materials, shearing or tearing of materials, or destruction or deformation of the materials utilized in the stop ring 240 and associated components.
Also, because the stop ring 240 is integrally formed in the nose piece 204, a separately provided stop ring common to known connectors, and the associated risks of incorrect installation or assembly of the piston stop and the connector, is substantially avoided. Because of the integration of the stop ring 240 into the nose piece 204 in a unitary construction, it may be ensured that the stop ring 240 is consistently positioned in a proper location within the contact passage 209 merely by installing the nose piece 204 to the contact tube. In an exemplary embodiment, and as shown in
Additionally, by integrating the stop ring 240 into the nosepiece construction, any chance of forgetting to install the stop ring is avoided, unlike known connectors having separately provided stop rings. With the integral nose piece 204 and stop ring 240, installation of the nose piece 204 guarantees the installation of the stop ring 240, and avoids inspection difficulties, or even impossibilities, to verify the presence of separately provided stop rings that are internal to the connector construction and are obstructed from view. A simpler and more reliable connector construction is therefore provided that is less vulnerable to incorrect assembly, installation, and even omission.
While integral formation of the stop ring 240 and the nose piece 204 is believed to be advantageous, it is recognized that the stop ring 240 may be a non-integral part of the nose piece 204 in other embodiments. For example, the stop ring 240 could be separately fabricated and provided from the nose piece 204, but otherwise coupled to or mounted to the nose piece 204 for reliable positioning of the stop ring 204 when the nose piece 204 is installed. As another example, the stop ring 242 could be otherwise provided and installed to the contact tube independently of the nose piece 204, while still providing shock absorbing piston deceleration in the contact tube.
Further, in alternative embodiments, the stop ring 240 may extend for less than the full circumference of nose piece 204, thereby forming alternative stop elements that engage only a portion of the piston face within the contact passage 209. Additionally, more than one shock absorbent stop element, in ring form or other shape, could be provided to engage different portions of the piston 222 during fault closure conditions. Still further, shock absorbent stop elements may be adapted to engage the female contact 224, or another part of the contact assembly 220, rather than the piston 222 to prevent overextension of the contact assembly 220 from the contact tube 222.
In an exemplary embodiment the connector 200 is a 600 A, 21.1 kV L-G loadbreak bushing for use with medium voltage switchgear or other electrical apparatus in a power distribution network of above 600V. It is appreciated, however, that the connector concepts described herein could be used in other types of connectors and in other types of distribution systems, such as high voltage systems, in which shock absorbent contact assembly stops are desirable.
The connector 200 is operable as follows.
During a loadbreak or switching operation, the male contact connector 102 (
In the joinder of the male connector 102 and the female connector 200 during loadmake, one connector is energized and the other is engaged with a normal load. Upon the attempted closure of male contact element 114 with the female contact 224, an arc is struck prior to actual engagement of the male contact element 114 with the female contact fingers 230 and continues until solid electrical contact is made therebetween. The arc passes from the male contact element 114 to the arc interrupter 228 and passes along the inner circumferential surface thereof, causing the generation of arc-quenching gases. These gases are directed inwardly within the female contact 224. The pressure of these gases applies a force to the arc snuffer housing 226 that in arc fault closure conditions is sufficient to overcome the frictional resistance of the contact piston 222, and the contact assembly 220, including the arc interrupter 228 and the arc snuffer housing 226 are moved from the normal position in
During fault closure, the arc-quenching gas pressure moves the entire contact assembly 220 in the direction of arrow B toward the male contact element 114 to more quickly establish electrical contact between male contact probe 114 and female contact fingers 230. This accelerated electrical connection reduces the fractional time required to make connection and thus reduces the possibility of hazardous conditions during a fault closure situation.
As show in
While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11192965 | Jul 2005 | US |
| Child | 12075209 | US |
