Abstract:
An adapter for connecting a 600 ampere deadbreak bushing to a pull-on and pull-off deadbreak elbow used for normally non-current carrying applications. The adapter comprises a two part separable assembly having first and second ends. The first end is threaded to mate with a threaded opening in the deadbreak bushing and the second end is threaded to mate with a threaded opening in a lug of the deadbreak elbow. The two part separable assembly is coupled together with the first part of the assembly that is screwed into the deadbreak bushing and has a groove that snaps (latches) into a corresponding latching ring in a molded insert of the deadbreak elbow that surrounds the second part of the assembly screwed into the lug inside of the deadbreak elbow. Other latching mechanisms may be used to mechanically and electrically couple together the first and second parts of the adapter assembly.

Description:
RELATED PATENT APPLICATION 
     This application claims priority to commonly owned U.S. Provisional Patent Application Ser. No. 61/347,216; filed May 21, 2010; entitled “Adapter for Bushing Latch,” by Paul Michael Roscizewski and David Charles Hughes; and is hereby incorporated by reference herein for all purposes. 
    
    
     TECHNICAL FIELD 
     The present invention relates generally to medium voltage connectors for dead front electrical equipment, and more particularly, to an adapter for interfacing a stab-on type arrestor elbow connector to a 600 ampere rated deadbreak bushing connector in the medium voltage electrical equipment. 
     BACKGROUND 
     In a typical power distribution network, substations deliver electrical power to consumers via interconnection cables and electrical apparatuses, e.g., transformers, switches, circuit breakers, fuses, etc. The cables terminate on bushings passing through walls of metal encased equipment, such as capacitors, transformers, switchgear, etc. Increasingly, this equipment is “dead front,” meaning that the equipment is configured such that an operator cannot make contact with any live electrical parts. Dead front systems have proven to be safer than “live front” systems, with comparable reliability and low failure rates. 
     Various safety codes and operating procedures for underground power systems require a visible disconnect between each cable and electrical apparatus to safely perform routine maintenance work, such as line energization checks, grounding, fault location, and hi-pot testing. One approach to meeting this requirement for a dead front electrical apparatus is to provide a “separable connector system” including a first connector assembly connected to the apparatus and a second connector assembly connected to an electric cable. The second connector assembly is selectively positionable with respect to the first connector assembly. An operator can engage and disengage the connector assemblies to achieve electrical connection or disconnection between the apparatus and the cable. 
     Generally, one of the connector assemblies includes a female style connector, and the other one of the connector assemblies includes a corresponding, male style connector. During a typical operation for making an electrical connection, an operator slides a female style connector over its corresponding male style connector. In some cases, each of the connector assemblies can include two connectors. For example, one of the connector assemblies can include ganged, substantially parallel female style connectors, and the other of the connector assemblies can include substantially parallel male style connectors that correspond to and are aligned with the female style connectors. 
     In general, two basic types of separable connector systems have conventionally been provided, namely, deadbreak connector systems and loadbreak connector systems. Deadbreak connector systems require connection or disconnection of cables while the equipment and the cables are de-energized. That is, deadbreak connectors are mated and separated only when there is no voltage present at and load current flowing through the connectors. A bolted connection is made such that the cable connector is screwed into the bushing with a coupling bolt in, e.g., a T-body 600 A deadbreak elbow. Deadbreak connector systems for high voltage equipment are typically rated for currents of 600 amperes. 
     To avoid power interruptions required by deadbreak connector systems, loadbreak connector systems have been developed that allow connection and disconnection to equipment when operating voltage and load current are present. This is done with a special arc interrupting probe tip in the loadbreak elbow. Loadbreak connector systems, however, are typically rated for much lower currents (typically about 200 amperes) than deadbreak connector systems. 
     The loadbreak elbow connector comprises an insulated portion having a recessed inner conical opening, a threaded lug, and a loadbreak probe with an arc follower tip portion. The loadbreak probe is screwed into the threaded lug coaxially within the inner conical opening. The loadbreak probe is made from a conductive material that contacts corresponding finger contacts into a mating loadbreak bushing connector to complete a circuit that includes the loadbreak elbow and the mating loadbreak connector. When mated together, an end of the male type conically shaped bushing connector is disposed substantially within the recessed inner conical opening of the loadbreak elbow. In this recessed inner conical opening, the loadbreak elbow includes a locking ring that is molded into the body of the loadbreak elbow connector that keeps the loadbreak elbow mechanically coterminous with the mating loadbreak male type bushing connector (e.g., loadbreak bushing). To connect and disconnect the loadbreak connectors, a person can manipulate the arrestor elbow onto and off of the male connector (e.g., loadbreak bushing) by using a liveline tool or “hot stick” in an operating eye of the loadbreak elbow to push on or pull off the loadbreak elbow with the loadbreak bushing The different mechanical and electrical mating interfaces of the 600 A deadbreak and 200 A loadbreak connectors are not compatible with one another, however, both use similar insulated mechanical conical portions of the male bushing and female elbow. 
     Transformers used in wind farm applications are generally equipped with 600 A deadbreak bushings. To obtain over voltage protection for the system, elbows having lightning or surge arrestors built-in (“arrestor elbows”) are attached to the transformer bushings. Traditionally, companies have only offered arrestors in 200 A loadbreak elbows, which, as set forth above, cannot be directly coupled to the 600 A deadbreak bushings. To compensate for this, companies have coupled intermediary connector adapters, such as an extender in combination with a loadbreak reducing tap plug (LRTP), between the standard 600 A deadbreak bushings and the 200 A arrestor loadbreak elbows. This approach is not desirable at least because the extra pieces required increase the cost of the installation and increase deadfront spacing requirements for this type of 600 A bushing—LRTP adapter-200 A arrestor elbow configuration. 
     SUMMARY 
     Therefore, what is needed is a less expensive and more compact adapter for interfacing a deadbreak 600 A bushing with a pull-on and pull-off arrestor elbow when used for normally non-current carrying applications, e.g., lightning and surge arrestors. This may be accomplished, according to the teachings of this disclosure, by providing an adapter for connecting a specially designed deadbreak elbow to the 600 ampere deadbreak bushing, configured in a form factor similar to a 200 ampere loadbreak elbow. This adapter comprises a two part separable assembly having first and second ends. The first end is threaded to mate with a threaded opening in the deadbreak bushing and the second end is threaded to mate with a threaded opening in a lug of the deadbreak elbow. The two part separable assembly is coupled together with the first part of the assembly that is screwed into the deadbreak bushing and has a groove that snaps (latches) into a corresponding latching ring in a molded insert of the deadbreak elbow that surrounds the second part of the assembly screwed into the lug inside of the deadbreak elbow. Other latching mechanisms may be used to mechanically and electrically couple together the first and second parts of the adapter assembly, e.g., barb and groove, latch ring, etc. The adapter assembly may also be spring loaded for increased electrical contact pressure (lower connection resistance). 
     According to a specific example embodiment of this disclosure, an adapter for coupling together a deadbreak bushing and a mating push-on/pull-off deadbreak arrestor elbow, comprises: a probe having a threaded end and a contact end opposite the threaded end thereof; and a socket having a threaded end and a contact end opposite the threaded end thereof; wherein: the threaded end of the probe screws into a connector in a deadbreak arrestor elbow, the threaded end of the socket screws into a threaded opening in a deadbreak bushing, and when the deadbreak arrestor elbow is placed onto the deadbreak bushing and forced thereover, the probe and socket contact ends make electrical and mechanical connection therebetween. 
     According to another specific example embodiment of this disclosure, an adapter for coupling together a deadbreak bushing and a mating deadbreak arrestor elbow comprises: a deadbreak probe having a threaded end and a contact end opposite the threaded end thereof; and a socket having a threaded end, a contact end opposite the threaded end thereof and a latching ring groove on an outside circumference of the socket and substantially coterminous with the contact end thereof; wherein: the threaded end of the non-loadbreak probe screws into a connector in a deadbreak arrestor elbow, the threaded end of the socket screws into a threaded opening in a deadbreak bushing, when the deadbreak arrestor elbow is placed onto the deadbreak bushing and forced thereover, the probe and socket contact ends make electrical connection therebetween, and wherein the latching ring groove fits onto a latching ring at an end of a conical opening of the deadbreak arrestor elbow, whereby the deadbreak bushing and the deadbreak arrestor elbow are thereby mechanically held together. 
     According to yet another specific example embodiment of this disclosure, a method of coupling together a deadbreak bushing and a mating deadbreak arrestor elbow comprises the step of: screwing a deadbreak probe into a connector in a deadbreak arrestor elbow; screwing a deadbreak socket into a treaded opening in a deadbreak bushing; and pushing the deadbreak arrestor elbow onto the deadbreak bushing, wherein the deadbreak probe and deadbreak socket make electrical and mechanical connection therebetween. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present invention and the advantages thereof, reference is now made to the following description, in conjunction with the accompanying drawings briefly described as follows. 
         FIG. 1  illustrates a schematic elevational exploded view of a cross section of a 600 A deadbreak bushing, push-on/pull-off deadbreak arrestor elbow and adapter therebetween, according to a specific example embodiment of this disclosure; 
         FIG. 2  illustrates a schematic elevational assembled view of a cross section of a mated 600 A bushing, push-on/pull-off deadbreak arrestor elbow and adapter therebetween as shown in  FIG. 1 , according to the specific example embodiment of this disclosure; 
         FIG. 3  illustrates a schematic elevational exploded view of a cross section of a 600 A deadbreak bushing, push-on/pull-off deadbreak arrestor elbow and adapter therebetween, according to another specific example embodiment of this disclosure; 
         FIG. 4  illustrates a schematic elevational assembled view of a cross section of a mated 600 A bushing, push-on/pull-off deadbreak arrestor elbow and adapter therebetween shown in  FIG. 3 , according to the another specific example embodiment of this disclosure; 
         FIG. 5  illustrates a schematic elevational exploded view of a cross section of a 600 A deadbreak bushing, push-on/pull-off deadbreak arrestor elbow and adapter therebetween, according to yet another specific example embodiment of this disclosure; and 
         FIG. 6  illustrates a schematic elevational assembled view of a cross section of a mated 600 A bushing, push-on/pull-off deadbreak arrestor elbow and adapter therebetween shown in  FIG. 5 , according to the yet another specific example embodiment of this disclosure. 
     
    
    
     While the present disclosure is susceptible to various modifications and alternative forms, specific example embodiments thereof have been shown in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific example embodiments is not intended to limit the disclosure to the particular forms disclosed herein, but on the contrary, this disclosure is to cover all modifications and equivalents as defined by the appended claims. 
     DETAILED DESCRIPTION 
     Referring now to the drawings, details of specific example embodiments of the present invention are schematically illustrated. Like elements in the drawings will be represented by like numbers, and similar elements will be represented by like numbers with a different lower case letter suffix. 
     Referring to  FIG. 1 , depicted is a schematic elevational exploded view of a cross section of a 600 A bushing, push-on/pull-off deadbreak arrestor elbow and adapter therebetween, according to a specific example embodiment of this disclosure. A conventional deadbreak male type connector commonly known in the industry as a “600 A deadbreak bushing” is represented by the numeral  128 . The bushing  128  includes an opening  126  having an internal 5/8-11 thread, which is configured for mechanically connecting to a corresponding threaded bolt of a mating connector (not shown), e.g., T-body or T-head elbow, whereby the bushing  128  and mating T-body connector (not shown) are both mechanically and electrically joined together. To connect and disconnect these types of 600 A deadbreak connectors, the threaded bolt assembly in the T-body elbow (not shown) is rotated until the threaded bolt is unscrewed from the threaded opening in the bushing  128 . Then the T-body elbow (not shown) may be removed from the 600 A deadbreak bushing  128  that is normally mounted on a dead front electrical equipment panel (not shown). 
     A push-on/pull-off deadbreak arrestor elbow is represented by the numeral  102 . This deadbreak arrestor elbow  102  comprises a molded EPDM insulation body  136  enclosing an electrical connector  110  having a threaded hole at an end opposite an attached surge or lightning arrestor  106 , an insulated pulling eye  104  is attached to the outside of the body  136  of the deadbreak arrestor elbow  102  in line with a conical opening  112  in the body  136 . The conically shaped opening  112  of the deadbreak arrestor elbow  102  is adapted to fit over the conically shaped bushing  128 . The bushing latch adapter, according to the teachings of this disclosure, allows for coupling the deadbreak arrestor elbow  102  to the standard 600 A deadbreak bushing  128  without requiring an additional loadbreak reducing tap plug (LRTP)(not shown). The surge or lightning arrestor  106  is connected to ground through a grounding wire  108 . 
     The bushing latch adapter of  FIG. 1  comprises a short non-loadbreak probe  116  and a mating socket  118 . The probe  116  has a threaded end  122  that screws into the connector  110 , and the socket  118  has a threaded end  124  that screws into the opening  126  of the bushing  128 . It is contemplated and within the scope of this disclosure that the socket  118  may or may not be spring loaded, and the probe  116  may be of a barb design for being held better in the socket  118 , or smooth for easily sliding into the socket  118 . 
     The probe  116  may be preassembled with the connector  110  in the deadbreak arrestor elbow  102  at the factory or in the field, and the socket  118  installed in the field on an existing 600 A bushing  128 . The socket  118  may have a latching ring groove  120  on an outside circumference of the end opposite the threaded end  124 , and be adapted to mate with a latching ring  114  molded into a semi-conductive insert  138  located inside of the insulated deadbreak arrestor elbow  102 . The latching ring  114  and the latching ring groove  120  mechanically engage and securely hold together the probe  116  and socket  118 . 
     To connect the bushing  128  and the deadbreak arrestor elbow  102  together, an electrician pushes the deadbreak arrestor elbow  102  onto the bushing  128  with a hot stick or liveline (not shown)(via the operating or pulling eye  104 ) so that the groove  120  engages the latching ring  114 . An interference fit or “latching force” between the groove  120  and the latching ring  114  securely and mechanically mates the bushing  128  and deadbreak arrestor elbow  102  together when the bushing  128  and deadbreak arrestor elbow  102  are electrically connected together. To disconnect the bushing  128  and deadbreak arrestor elbow  102 , the electrician pulls the deadbreak arrestor elbow  102  off of the bushing  128  with the hot stick or liveline (not shown)(via the operating eye  104 ), with sufficient force to overcome the latching force between the groove  120  and latching ring  114 . A person of ordinary skill in the art and having the benefit of the present disclosure will recognize that many other alternative latching mechanisms may be used, and are contemplated herein. 
     Referring to  FIG. 2 , depicted is a schematic elevational assembled view of a cross section of a 600 A bushing, push-on/pull-off deadbreak arrestor elbow and adapter therebetween shown in  FIG. 1 , according to the specific example embodiment of this disclosure. The bushing  128  and elbow  102  are coupled together as shown and remain securely together with the mechanical cooperation of the groove  120  and latching ring  114 . 
     Referring to  FIG. 3 , depicted is a schematic elevational exploded view of a cross section of a 600 A bushing, push-on/pull-off deadbreak arrestor elbow and adapter therebetween, according to another specific example embodiment of this disclosure. The bushing  128  and elbow  102  are the same as those described in  FIG. 1  hereinabove. The bushing latch adapter of  FIG. 3  comprises a short non-loadbreak probe  316 , and a mating socket  318  having a slideable electrical contact  317  and a loading spring  340  therein. The probe  316  has a threaded end  322  that screws into the connector  110 , and the socket  318  has a threaded end  324  that screws into the opening  126  of the bushing  128 . The loading spring  340  is used for biasing the slideable electrical contact  317  toward a contact end of the probe  316  for reducing electrical contact resistance therebetween. 
     The probe  316  may be preassembled with the connector  110  in the deadbreak arrestor elbow  102  at the factory or in the field, and the socket  318  installed in the field on an existing 600 A bushing  128 . The socket  318  may have a latching ring groove  320  on an outside circumference of the end opposite the threaded end  324 , and be adapted to mate with a latching ring  114  molded into a semi-conductive insert  138  located inside of the insulated deadbreak arrestor elbow  102 . The latching ring  114  and the latching ring groove  320  mechanically engage and securely hold together the probe  316  and socket  318 . 
     Referring to  FIG. 4 , depicted is a schematic elevational assembled view of a cross section of a 600 A bushing, push-on/pull-off deadbreak arrestor elbow and adapter therebetween shown in  FIG. 3 , according to the another specific example embodiment of this disclosure. The bushing  128  and elbow  102  are coupled together as shown and remain securely together with the mechanical cooperation of the groove  320  and latching ring  114 . In addition, the loading spring  340  biases the slideable electrical contact  317  toward a contact end of the probe  316  for reducing electrical contact resistance therebetween. 
     Referring to  FIG. 5 , depicted is a schematic elevational exploded view of a cross section of a 600 A bushing, push-on/pull-off deadbreak arrestor elbow and adapter therebetween, according to yet another specific example embodiment of this disclosure. The bushing  128  and elbow  102  are the same as those described in  FIG. 1  hereinabove. The bushing latch adapter of  FIG. 5  comprises a short non-loadbreak probe  516 . The probe  516  has a threaded end  522  that screws into the connector  110 , and the socket  518  has a threaded end  524  that screws into the opening  126  of the bushing  128 . The probe  516  is configured into a barb shape at end  532  that mechanically cooperates with an internal latching ring  530  inside of the opening of the socket  518  to mechanically hold the probe  516  and socket  518  together when the elbow  102  is forced over the bushing  128 . 
     The probe  516  may be preassembled with the connector  110  in the deadbreak arrestor elbow  102  at the factory or in the field, and the socket  518  installed in the field on an existing 600 A bushing  128 . The socket  518  has a latching ring  530  on an inside circumference of the end opposite the threaded end  524 , and is adapted to mate with a barbed portion of the probe  516 . The latching ring  530  and the barbed portion of the probe  516  mechanically engage and securely hold together the probe  516  and socket  518 . A biasing collar  528  may further be used to increase compressive tension between the latching ring  530  and the barbed portion of the probe  516 . 
     Referring to  FIG. 6 , depicted is a schematic elevational assembled view of a cross section of a 600 A bushing, push-on/pull-off deadbreak arrestor elbow and adapter therebetween shown in  FIG. 5 , according to the yet another specific example embodiment of this disclosure. The bushing  128  and elbow  102  are coupled together as shown and remain securely together with the mechanical cooperation of the latching ring  530  and the barbed portion of the probe  516 . 
     Although specific example embodiments of the invention have been described above in detail, the description is merely for purposes of illustration. It should be appreciated, therefore, that many aspects of the invention were described above by way of example only and are not intended as required or essential elements of the invention unless explicitly stated otherwise. Various modifications of, and equivalent steps corresponding to, the disclosed aspects of the exemplary embodiments, in addition to those described above, can be made by a person of ordinary skill in the art, having the benefit of this disclosure, without departing from the spirit and scope of the invention defined in the following claims, the scope of which is to be accorded the broadest interpretation so as to encompass such modifications and equivalent structures.