Abstract:
A line protection system described herein provides reliable electro-mechanical connections between system components, reduces mechanical stresses on a disconnector, assures more effective disconnection of a failed arrestor, and is lower in cost than existing systems. The line protection system includes a surge arrestor, a disconnector coupled to the surge arrestor, and a line lead coupled to the disconnector. The line lead generally is a high strength cable and/or the line protection system generally does not include a shunt bypass assembly. Upon exposure to a high voltage condition, the disconnector actuates and separates the line lead from the system.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application No. 61/311,458, titled “Line Protection Systems” filed on Mar. 8, 2010, the entire disclosure of which is hereby fully incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to an assembly of a disconnector, a surge arrestor, and an insulator for connecting a power distribution or transmission line to ground. More particularly, the present invention involves distribution or transmission line protection systems having two disconnectors in series, a high strength stainless steel line lead, and/or conductive connectors that reduce mechanical stresses on the system and/or allow reliable electro-mechanical connections. 
     BACKGROUND OF THE INVENTION 
     Power distribution or transmission lines are typically suspended from towers by insulators, which serve to electrically insulate line voltage from ground, and additionally prevent electrical power current from flowing from the distribution or transmission line to the supporting tower. Transient overvoltage conditions caused by current flows may lead to insulator flashover, resulting in a system outage and potential damage to the insulator and conductors. 
     To reduce or eliminate insulator flashover, a surge arrestor is typically used in parallel with an insulator. Surge arrestors are typically connected to power distribution or transmission lines to carry electrical surge currents to ground, and thus, prevent damage to the lines, as well as the equipment connected thereto. Surge arrestors generally offer high resistance to normal voltage across distribution or transmission lines, and provide very low resistance to surge currents produced by sudden high voltage conditions, such as those caused by a lightning strike, and thereby reduce the risk of insulator flashover during surge events. After the surge currents cease, the voltage drops and the surge arrestor returns to a high resistance condition. However, in certain cases when the surge arrestor fails, the high resistance condition is not resumed, and the surge arrestor continues to provide an electrical path from the distribution or transmission line to the ground. As a result of arrestor failure, the distribution or transmission line will lockout. 
     Disconnectors (or disconnecting devices) are commonly used in combination with the surge arrestors to separate failed surge arrestors from the circuit. The surge arrester/disconnector assembly is connected in parallel with the insulator. In certain arrangements, the surge arrestor is connected to the distribution or transmission line by a copper or aluminum line lead, a disconnector, and a number of moving, wearable connections between the components which include shunt bypass assemblies that provide solid, partial discharge free electrical contact around the associated moveable, wearable connections. The disconnectors provide a visual indication of surge arrestor failure upon actuation of the disconnectors. The disconnectors have an explosive charge to physically separate the terminals of the disconnector when actuated. Operation of the disconnector effectively removes the failed arrester from the circuit. Once the fault has been cleared, the power system circuit can be reenergized without the failed arrester in the circuit. In some cases, upon actuation of the disconnector, the line lead, which is still connected to ground, swings uncontrollably unless weights, such as chains, are attached so that the line lead falls to a safe location to prevent unintentional short circuits from accidentally coming in contact with a conductor. However, the weights on the line lead provide added mechanical stresses on the disconnector, as well as added costs due to added components. 
     Therefore, a need exist in the art for an improved line protection system that provides more reliable electro-mechanical connections between system components, reduces mechanical stresses on the disconnector, assures more effective disconnection of a failed arrestor, and is lower in cost than existing systems. 
     SUMMARY OF THE INVENTION 
     The present invention provides a line protection system that is safer, more reliable, and lower in cost than existing systems. 
     In one aspect of the invention, a line protection system can include a surge arrestor, a line lead, and two disconnectors. One of the disconnectors can be coupled to the surge arrestor and a first end of the line lead, while the other disconnector can be coupled to a second end of the line lead. When the system is exposed to a high voltage condition, the surge arrestor can fail, and thereby cause the line lead to separate at both of the disconnectors. The line lead can then fall to the ground. 
     In another aspect, a line protection system can include a surge arrestor, a disconnector, and a line lead. The disconnector can be coupled to the surge arrestor and the line lead. The line lead can include a high strength cable. The line protection system does not include a shunt bypass assembly. 
     In yet another aspect, a line protection system can include a surge arrestor, a disconnector coupled to the surge arrestor by a conductive connector, and a line lead coupled to the disconnector by another conductive connector. The conductive connector can be a ball swage and shackle connector, a threaded swage connector, or a pad swage connector. The line protection system can be without a shunt bypass assembly. 
     These and other aspects, objects, features, and embodiments of the present invention will become apparent to those having ordinary skill in the art upon consideration of the following detailed description of illustrative embodiments exemplifying the best mode for carrying out the invention as presently perceived. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the exemplary embodiments of the present invention and the advantages thereof, reference is now made to the following description in conjunction with the accompanying drawings, which are described below. 
         FIG. 1A  is a perspective view of a line protection system for power distribution, according to an exemplary embodiment. 
         FIG. 1B  is a perspective view of the line protection system of  FIG. 1A , after system failure, according to an exemplary embodiment. 
         FIG. 2  is a perspective view of a ball swage and shackle connector, coupled to a cable and a mounting bracket, according to an exemplary embodiment. 
         FIG. 3  is a side view of another ball swage and shackle connector, coupled to a cable and a disconnector, according to an exemplary embodiment. 
         FIG. 4A  is a perspective view of a threaded swage connector, coupled to a cable and a line tap, according to an exemplary embodiment. 
         FIG. 4B  is a perspective view of the threaded swage connector of  FIG. 4A , coupled to a cable and a surge arrestor, according to another exemplary embodiment. 
         FIG. 5  is a front view of a pad swage connector, coupled to a cable and a pad, according to an exemplary embodiment. 
         FIG. 6  is a side view of a dual disconnector-arrestor system, according to another exemplary embodiment. 
         FIG. 7  is a front view of a dual disconnector system, according to an exemplary embodiment. 
         FIG. 8  is a side view of a line protection system for transmission applications, according to an exemplary embodiment. 
         FIG. 9  is a side view of a line protection system for transmission applications, according to another exemplary embodiment. 
     
    
    
     The drawings illustrate only exemplary embodiments of the invention and are therefore not to be considered limiting of its scope, as the invention may admit to other equally effective embodiments. The elements and features shown in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of exemplary embodiments of the present invention. Additionally, certain dimensions may be exaggerated to help visually convey such principles. In the drawings, reference numerals designate like or corresponding, but not necessarily identical, elements. 
     DETAILED DESCRIPTION OF THE INVENTION 
     A line protection system described herein generally includes a surge arrestor, at least one disconnector, at least one conductive connector, and at least one line lead. In some embodiments, two disconnectors may be used in conjunction with a high strength stainless steel line lead. Generally, the line protection systems of the present invention create more reliable electro-mechanical connections between system components, thereby providing greater longevity than existing line protection systems in the market. The benefits of the line protection system of the present invention are to reduce the mechanical stresses on the disconnector, and eliminate the number of troublesome moving, wearable connections having shunt bypass assemblies that are common in existing designs. 
     The invention may be better understood by reading the following description of non-limiting, exemplary embodiments with reference to the attached drawings wherein like parts of each of the figures are identified by the same reference characters. 
       FIG. 1A  is a perspective view of a line protection system for power distribution application  100 , according to an exemplary embodiment.  FIG. 1B  is a perspective view of a line protection system for power distribution application  100  after system failure, according to an exemplary embodiment. The line protection system for power distribution application  100  includes a surge arrestor  102 , disconnectors  104 ,  106 , insulators  108 , and a line lead  110 . The surge arrestor  102  can be any surge arrestor suitable for use with a transmission or distribution line. The surge arrestor  102  is coupled to a utility structure  112  by an insulating hanger  112   a . In certain embodiments, the utility structure  112  is a pole or a tower. A bottom end  102   a  of the surge arrestor  102  is coupled to a ground lead  114  that is connected to ground. A top end  102   b  of the surge arrestor  102  is coupled to the disconnector  104  by a cable  116  and a conductive connector  118 . The disconnector  104  is coupled to the line lead  110  by a conductive connector  120 , which is also coupled to the disconnector  106  by a conductive connector  122 . The disconnector  106  is coupled to a line clamp  124  by a conductive connector  126  and a cable  128 , and the line clamp  124  is connected to a distribution line  130 . The distribution line  130  is coupled to an insulator  108  that is coupled to the structure  112 . In certain embodiments, the insulator  108  is a pin insulator. Referring to  FIG. 1B , when a high voltage condition occurs, such as a lightning strike, the disconnectors  104 ,  106  are actuated and separate. As a result, the line lead  110  is separated from the system for power distribution  100  and coils upon itself, and falls to the surface  132  below. 
     The disconnectors  104 ,  106  can be any disconnecting device suitable for use with a surge arrestor. Suitable disconnectors include disconnectors having cartridge detonators or potassium chlorate detonators. 
     The line lead  110  is preferably made from a material, such as a high strength stainless steel cable, that is able to coil into a circle upon disconnection from the disconnectors  104 ,  106 . Suitable cables for line leads include high strength cable assemblies having a tensile strength of greater than about 2500 pounds per square inch. The line lead  110  can be of any length. In certain exemplary embodiments, the length of the line lead  110  is from about six feet to about ten feet. In other exemplary embodiments, the length of the line lead  110  is about twenty feet. In certain alternative embodiments, the line lead  110  is constructed of stranded copper or aluminum. 
     The connectors  118 ,  120 ,  122 , and  126  can be any suitable conductive connector for coupling a cable to a disconnector. Examples of suitable connectors include, but are not limited to, ball swage and shackle connectors, threaded swage connectors, and pad swage connectors. The connectors  118 ,  120 ,  122 , and  126  may be constructed from any conductive material, such as stainless steel, brass, copper, and aluminum. The inclusion of the connectors  118 ,  120 ,  122 , and  126  allows for the application of an axial load across the disconnectors  104 ,  106 , and helps prevent premature failures that result from sheer loads from conventional methods. Suitable connectors are described in further detail with respect to  FIG. 2-5 . 
       FIG. 2  is a perspective view of a conductive ball swage and shackle connector  200  coupled to a cable  202  and a mounting bracket  204 , according to an exemplary embodiment. The connector  200  includes a ball swage portion  206  and a shackle portion  208 . The ball swage portion  206  includes a clearance set sleeve  210  that the cable  202  is inserted into. The sleeve  210  is compressed into strands of the cable  202  to create a mechanical bond that secures the connector  200  to the cable  202 . In certain exemplary embodiments, the sleeve  210  is crimped to the cable  202 . The ball swage portion  206  also includes spherical-shaped portion  212  coupled to the sleeve  210 . The shackle portion  208  is generally U-shaped or horseshoe-shaped with a base  208   a  and two parallel extensions  208   b  extending orthogonally therefrom. The spherical-shaped portion  212  of the ball swage portion  206  is positioned at the base  208   a  of the shackle portion  208 , and the sleeve  210  extends through an opening (not shown) in the base  208   a  in a direction away from the extensions  208   b . In certain exemplary embodiments, the spherical-shaped portion  212  is rotatable within the opening in the base  208   a  for a movable connection, thus allowing for untwisting of the cable  202  as needed and stress release. The mounting bracket  204  is positioned between the extensions  208   b , and each of the extensions  208   b  includes an opening (not shown) at an end thereof for receiving a securing mechanism  216  for securing the extensions  208   b  to the mounting bracket  204 . 
       FIG. 3  is a side view of a conductive ball swage and shackle connector  300  coupled to a cable  302  and a disconnector  304 , according to an exemplary embodiment. The connector  300  includes a ball swage portion  306  and a shackle portion  308 . The ball swage portion  306  includes a clearance set sleeve  310  that the cable  302  is inserted into. The sleeve  310  is similar to the sleeve  210 , and secures the connector  300  to the cable  302 . The ball swage portion  306  also includes spherical-shaped portion  312  coupled to the sleeve  310 . The shackle portion  308  is generally U-shaped or horseshoe-shaped with a base  308   a  and two parallel extensions  308   b  extending orthogonally therefrom. In certain embodiments, ends  308   c  of the extensions  308   b  angle towards each other, and are in contact with one another. The spherical-shaped portion  312  of the ball swage portion  306  is positioned at the base  308   a  of the shackle portion  308 , and the sleeve  310  extends through an opening (not shown) in the base  308   a  in a direction away from the extensions  308   b . In certain exemplary embodiments, the spherical-shaped portion  312  is rotatable within the opening in the base  308   a  for a movable connection, thus allowing for untwisting of the cable  302  as needed and stress release. Each of the ends  308   c  includes an opening (not shown) for receiving a securing mechanism, such as bolt  316  for securing the ends  308   c  to the disconnector  304 . 
       FIG. 4A  is a perspective view of a conductive threaded swage connector  400  coupled to a cable  402  and a line tap  404  for connecting to a transmission line (not shown), according to an exemplary embodiment. The connector  400  includes a cylindrical portion  406  and a clearance set sleeve  410 . The sleeve  410  is similar to the sleeve  210 , and secures the connector  400  to the cable  402 . The cylindrical portion  406  includes a cavity (not shown) having female threads (not shown) therein. The female threads mate with corresponding male threads (not shown) on the line tap  404  to secure the line tap  404  to the connector  400 . 
       FIG. 4B  is a perspective view of the conductive threaded swage connector  400  coupled to the cable  402  and a surge arrestor  414 , according to an exemplary embodiment. The cylindrical portion  406  of the connector  400  includes female threads therein for mating with corresponding male threads (not shown) on the surge arrestor  414 , and thus securing the connector  400  to the surge arrestor  414 . 
       FIG. 5  is a front view of a conductive pad swage connector  500  coupled to a cable  502  and a pad  504 , according to an exemplary embodiment. The connector  500  includes a terminal spade  506  and a clearance set sleeve  510 . The sleeve  510  is similar to the sleeve  210 , and secures the connector  500  to the cable  502 . The terminal spade  506  is generally flat, and includes an opening (not shown) in which a securing mechanism  516  is position for securing the terminal spade  506  to the pad  504 . 
       FIG. 6  is a side view of a dual disconnector-arrestor system  600 , according to an exemplary embodiment. The dual disconnector-arrestor system  600  includes a surge arrestor  602 , disconnectors  604 ,  606 , and a line lead  608 . One end  602   a  of the surge arrestor  602  is coupled to the disconnector  604  by a conductive L-shaped conductive plate  614 . The disconnector  604  is coupled to the line lead  608  by the conductive ball swage and shackle connector  300  ( FIG. 3 ). The line lead  608  is also coupled to the disconnector  606  by the conductive threaded swage connector  400  ( FIGS. 4A-4B ). The disconnector  606  is coupled directly to a line clamp  622 , and the line clamp  622  can further be connected to a distribution or transmission line (not shown). Upon actuation and separation of the disconnectors  604 ,  606 , the line lead  608  coils upon itself and separates entirely from the system  600 . 
       FIG. 7  is a front view of a dual disconnector system  700 , according to an exemplary embodiment. The dual disconnector system  700  includes two disconnectors  704 ,  706 , and a high strength stainless steel line lead  708 . The disconnector  704  is coupled to a cable  714  by the pad swage connector  500  ( FIG. 5 ). The disconnector  704  is also coupled to the line lead  708  by the threaded swage connector  400  ( FIG. 400 ). The disconnector  706  is coupled to an opposite end of the line lead  708  by another threaded swage connector  400  ( FIG. 400 ). The disconnector  706  is further coupled to a cable  726  by the ball swage and shackle connector  200  ( FIG. 2 ). 
       FIG. 8  is a side view of a line protection system for transmission applications  800 , according to an exemplary embodiment. The line protection system for transmission applications  800  includes a surge arrestor  802 , a disconnector  804 , a transmission line conductor  806 , an insulator  808 , and a line lead  810 . The surge arrestor  802  can be any surge arrestor suitable for transmission line protection. The line lead  810  is a high strength cable. The insulator  808  is suspended from a crossarm  812   a  extending from a transmission tower  812 . The transmission line conductor  806  is coupled to a bottom end  808   a  of the insulator  808 . A bottom end  802   a  of the surge arrestor  802  is coupled to the insulator  808  by a rigid mechanical support  814  having a hinge point  814   a . A top end  802   b  of the surge arrestor  802  is coupled to the disconnector  804  by the line lead  810 . The disconnector  804  is coupled to a top end  808   b  of the insulator  808 , and thereby the surge arrestor  802  is parallel to the insulator  808 . When a high voltage condition occurs, such as a lightning strike, the disconnector  804  is actuated and separates. As a result, the surge arrestor  802  is electrically separated from the system for transmission applications  800 . 
       FIG. 9  is a side view of a line protection system for transmission applications  900 , according to another exemplary embodiment. The line protection system for transmission applications  900  includes a surge arrestor  902 , disconnectors  904   a ,  904   b , a transmission line conductor  906 , an insulator  908 , and a line lead  910 . The surge arrestor  902  can be any surge arrestor suitable for transmission line protection. The line lead  910  is a high strength cable. The insulator  908  is suspended from a crossarm  912   a  extending from a transmission tower  912 . The transmission line conductor  906  is coupled to a bottom end  908   a  of the insulator  908 . The transmission line conductor  906  is coupled to a top end  902   b  of the surge arrestor  902  by a high strength cable  914 . A bottom end  902   a  of the surge arrestor  902  is coupled to the disconnector  904   a  by a cable  916 . The disconnector  904   a  is coupled to the disconnector  904   b  by the line lead  910 . The disconnector  904   b  is coupled to the transmission tower  912  by a cable  920 . When a high voltage condition occurs, such as a lightning strike, the disconnectors  904   a ,  904   b  are actuated and separate. As a result, the line lead  910  is separated (not shown) from the system for transmission applications  900  and coils upon itself, and falls to the surface below. 
     Therefore, the present invention is well adapted to attain the ends and advantages mentioned as well as those that are inherent therein. The particular embodiments disclosed above are illustrative only, as the present invention may be modified and practiced in different but equivalent manners apparent to those having ordinary skill in the art having the benefit of the teachings herein. Having described some exemplary embodiments of the present invention, it is believed that the use of alternate conductive connector configurations is within the purview of those having ordinary skill in the art. In addition, the connector configurations may be used in other power applications, such as in distribution power delivery and power transmission applications. While numerous changes may be made by those having ordinary skill in the art, such changes are encompassed within the spirit of this invention as defined by the appended claims. It is therefore evident that the particular illustrative embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the present invention as defined by the claims below. The terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee.