Abstract:
A cable connector, connector apparatus and method for introducing fluid to a cable. The cable connector, connector apparatus and method configured to form an electrically resistive barrier between components internal to the connector and the environment surrounding the connector after the introduction of the fluid. In one embodiment, a connector comprises a chamber adapted to affix a cable internal to the chamber, wherein the chamber is in fluidic communication with an injection port. The connector further comprises a valve operable to restrict fluid from entering the injection port from the chamber when a fluid source discontinues the introduction of fluid into the injection port. In another embodiment, a method of the present invention involves the application of an insulating material into an injection port of a connector following the application of a dielectric fluid, thereby forming an electrically resistive barrier between components internal to the connector and the external environment.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This non-provisional application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Application No. 60/251,974, filed on Dec. 6, 2000, and titled “Method and Apparatus for Blocking Pathways Between a Power Cable and the Environment,” the subject matter of which is specifically incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a remediation process for the insulation of power cables and, more particularly, to injection of dielectric enhancement component into the power cable. 
     BACKGROUND OF THE INVENTION 
     A remediation process for the insulation of high-voltage electrical power cables requires the injection of a remediation fluid into the cables. It is known in the art that remediation fluids which are most effective have viscosities less than 50 centistokes at 25° C. as these fluids must be able to flow through very small interstitial spaces over very long cable lengths and must be of small enough molecular size to diffuse into the cable insulation. In many instances, this injection process takes place while the cable is energized. When the remediation process is performed on energized cables, a class of special cable end terminations is typically used. These terminations are known as injection elbows. Injection elbows are similar to industry standard elbow-type connectors except that special ports have been designed into them to allow for the attachment of an injection plug to the elbows. 
     After injection of the remediation fluid is complete, the injection plug is withdrawn from the injection port and is replaced with a sealing plug. Between the time that the injection plug is removed, and the sealing plug is installed, the injection port is open, and the energized conductor of the cable is exposed. Because of the remediation fluid&#39;s low viscosity it is likely to empty out of the open injection port. Although there is no direct electrical connection between the conductor and the grounded exterior of the cable elbow, there is the danger of an indirect electrical connection being established between the conductor and the grounded exterior of the elbow. 
     One such indirect pathway may be formed by contaminants that have become entrained in the remediation fluid. Contaminated fluid can be drawn from the injection port as the injection plug is withdrawn or may simply flow out under the force of gravity, thereby creating partial discharging or even a complete conductive pathway to the ground plane. 
     A second indirect pathway is created by source molecules such as those found in low viscosity remediation fluid, water or other contaminants which may be present in the conductor. Source molecules, also referred to as particles, can ionize or form an aerosol, which may become charged in the high-voltage field. These ionized or charged particles may then accelerate towards the ground plane creating a dynamic and conductive aerial pathway. 
     These two known conductive pathways, as well as any other conductive pathway established between the conductor and the ground plane, can degrade or destroy the injection elbow. Therefore, a need exists to create a barrier to block the conductive pathway between the conductive portion of the cable and the ground plane to increase the life expectancy of the injection elbow. 
     SUMMARY OF THE INVENTION 
     One embodiment of the present invention is directed towards a method and apparatus for creating a barrier after the injection of remediation fluid to block the conductive pathway between the conductive portion of an energized cable and the ground plane. An injection elbow with an injection port is used to introduce remediation fluid into the energized cables. The remediation fluid is introduced into the injection port by way of an injection plug inserted into the injection port. Upon completion of the introduction of the remediation fluid, an insulation material is injected through an injection tube of the injection plug and into the injection port. This insulation material may be any of a variety of dielectric, high-viscosity fluids. The insulation material effectively blocks the conductive pathway between the conductive portion of the cable and the ground plane so as to allow removal of the injection plug without creation of a conductive pathway to allow for the insertion of a permanent plug to block the injection port and protect the injection elbow from degradation. 
     In another embodiment of the present invention, the injection elbow includes a flap valve located between the injection port and a fluid chamber inside the injection elbow. As fluid is introduced through the injection port, the flap valve is opened either by the fluid pressure, or by an extension on the injection plug, allowing the fluid to fill a chamber in the injection elbow. When the chamber in the fluid elbow is full and introduction of the fluid has ceased, the pressure from inside the chamber forces the flap valve to shut, thus creating a barrier between the conductor and the ground plate. The injection plug can now be removed without exposing the energized conductor which may create a degradation of the injection elbow. 
     In still another embodiment of the present invention, a physical barrier is incorporated in the injection plug to block the escape of remediation fluid upon discontinuing filling of the chamber of the injection elbow. This embodiment permits leaving behind the injection plug in the injection port thus eliminating a need for a permanent plug. The physical barrier of this embodiment includes a ball valve; however, a variety of gate valves or check valves, actuated manually, electronically, hydraulically, or pneumatically may be used. 
     In yet another embodiment of the present invention, the injection plug includes a breakable tip having a catch at its end. Upon insertion of the injection tube into the injection port, the breakable tip becomes lodged in the injection port. After discontinuing the introduction of remediation fluid into the chamber, the injection plug is removed causing the breakable tip of the injection tube to remain lodged in the injection port creating a permanent barrier in the injection port, therefore, blocking the conductive pathway between the conductive portion of the cable and the ground plane. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein: 
     FIGS. 1A and 1B illustrate a cross-sectional side view of an injection elbow formed in accordance with one embodiment of the present invention, showing an injection plug, and a sealing plug; 
     FIG. 2 illustrates a cross-sectional side view of an injection elbow formed in accordance with one embodiment of the present invention, showing a flap valve at the junction of the injection port and the chamber; 
     FIG. 3 illustrates a cross-sectional side view of an injection plug formed in accordance with one embodiment of the present invention, showing a ball valve and a ball valve override apparatus; 
     FIG. 4 illustrates a cross-sectional side view of an injection plug with a ball valve formed in accordance with one embodiment of the present invention; and 
     FIG. 5 represents a cross-sectional side view of an injection plug formed in accordance with one embodiment of the present invention, showing an injection tube having a breakable tip and a catch. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIGS. 1A and 1B illustrate an injection elbow  10  formed in accordance with one embodiment of the present invention. Such an injection elbow  10  is adapted to introduce dielectric enhancement fluid into a section of power cable  2 , such as a high-voltage electric cable. Typical power cables  2  include a conductive core  4  surrounded by an insulation layer  6 . The conductive core  4  includes a plurality of electrically conductive strands  13 . Although a plurality of conductive strands  13  is preferred, a cable  2  having a single conductive strand is also within the scope of the present invention. Further, although the injection elbow  10  is illustrated as a load-break connector, other types of connectors, such as tee-body or splice-type connectors which occur at cable junctions, are also within the scope of the present invention. 
     The elbow  10  includes a fluid chamber  12  and an injection port  14 . The injection port  14  permits the introduction of the dielectric enhancement fluid into the cable while the cable is energized. Dielectric enhancement fluid is injected through the injection port  14  and into the fluid chamber  12  by a canal  15 , thus allowing fluid to enter the cable insulation through the interstitial spaces between the cable strands. 
     Still referring to FIG. 1, fluid enters the injection port  14  by way of an injection plug  20 . The injection plug  20  includes a conduit  24  and a stem portion  22 . In operation, the stem portion  22  is inserted into the injection port  14  to allow for the introduction of the dielectric enhancement fluid into the fluid chamber  12 . A permanent plug  16  is sized and shaped for insertion into the injection port  14 , thereby sealing the chamber  12  from the environment external to the injection elbow  10 . In operation, the permanent plug  16  is inserted into the injection port  14  after the removal of the injection plug  20 . 
     As noted above, it is desirable to minimize the risk of a pathway being formed between the conductive portions  4  and  6 , of the cable  2  and the external environment. In that regard, before the injection plug  20  is removed from within the injection elbow  10 , an insulation material  15  is injected into the injection port  14 . The insulation material  15  forms a barrier to block any pathway between the conductor and ground, including minimizing the risk of the formation of a conductive pathway through the injection port  14 . Thereafter, the injection plug  20  is removed from the injection port  14 , and the plug  16  is reinserted into the injection port  14  of the injection elbow  10 . 
     Thus, one embodiment of a method for blocking a potential pathway between the conductive core  4  of a cable  2  and a ground plane after removal of the injection plug  20  includes inserting the injection tube  22  of the injection plug  20  into the injection port  14  of the injection elbow  10 ; introducing a dielectric enhancement fluid into the injection port  14  from the injection plug  20  and into the fluid chamber  12  where it surrounds the conductive core  4  and strands  13 ; injecting an insulation material  15  through the injection plug  20  and into the injection port  14 , whereby the insulation material  15  forms a barrier to block the potential pathway out through the injection port  14 ; and removing the injection plug  20  and replacing it with the plug  16 . 
     The insulation material  15  is suitably a high dielectric strength, high viscosity material. Because of the material&#39;s high viscosity, it remains in place to form a physical barrier between any conductive portion of a cable and the ground plane until the plug  16  can be installed. The insulating fluid  15  can be in the form of a foam, solid, gel, or high viscosity liquid. In one embodiment, the dielectric strength may be greater than 100 volts/mil and the viscosity may be greater than 50 centistokes (cs) at 25C. In this embodiment, the dielectric strength and viscosity should be in a range that allows the insulation material  15  to contain liquid properties. One specific example of an insulating material is Dow Corning 200® fluid. Although the present embodiment uses fluid with a viscosity of 2000 centistoke, any of a variety of high dielectric strength, high viscosity materials may be used. 
     FIG. 2 illustrates another embodiment of an injection elbow  110  constructed in accordance with the present invention. The injection elbow  110  is identical in materials and operation to the first embodiment described above with the exception that the injection elbow  110  includes a flap valve  130 . In one embodiment, the flap valve  130  is suitably located at the intersection of the injection port  114  and the fluid chamber  112 . The flap valve  130  may be integrally connected to the injection elbow  110  by a live hinge, or may be fastened to the injection elbow  110  by a mechanical hinge  131 . In one embodiment, the flap valve  130  is normally biased into a closed position. Although the illustrative embodiment of FIG. 2 includes a flap valve  130  that is located near the intersection of the injection port  114  and the fluid chamber  112 , the flap valve  130  may be positioned in any location of the injection port  114  and fluid chamber  112  so long as the flap valve  130  is configured to restrict any fluidic communication from the fluid chamber  112  to the injection port  114 . For instance, the flap valve  130  may be constructed from a substantially flat member attached to the inner wall of the injection port  114  by the use of a hinge. 
     As dielectric enhancement fluid is introduced into the injection port  114 , the flap valve  130  is forced open by the fluid pressure of the incoming dielectric enhancement fluid, or it is physically opened by an extended length injection fitting, thereby allowing the fluid to enter or exit the chamber  112 . When introduction of the fluid has concluded, the flap valve  130  returns to the closed position, thereby creating a physical barrier between the conductive core  104  and the ground plane. 
     Referring now to FIG. 3, another embodiment of an injection plug  220  constructed in accordance with the present invention will now be described in greater detail. The injection plug  220  is identical in materials and operation to the injection plug  220  described for the first embodiment with the exception that the injection plug  220  is constructed and configured to remain attached to the injection elbow  10 , and includes a plunger assembly  239  and a valve actuator assembly  234 . The injection plug  220  is configured to remain attached to the injection elbow  10  after the introduction of dielectric enhancement fluid. As such, it should be apparent that dielectric enhancement fluid is introduced to the injection plug  220  by a removable supply source  280 . In operation, the injection plug  220  is accessed in a well known fashion and the supply source  280  is removably coupled to the injection plug  220 . After the transfer of dielectric enhancement fluid has been completed, the supply source  280  is decoupled from the injection plug  220 . Although a fixed injection plug  220  is suitable for purposes of the current embodiment of the present invention, it should be apparent that other types of injection plugs, such as temporary injection plugs, are also within the scope of the present invention. 
     The plunger assembly  239  includes a plunger  231  and a spring bias ball valve  232 . The plunger  231  is suitably a rod shaped member slidably disposed within the conduit  224  of the stem portion  222 . As disposed within the stem portion  222 , the plunger extends between the valve actuator assembly  234  and the ball valve  232 . 
     The ball valve  232  includes a spring  236  and a ball  238 . The spring  236  biases the ball  238  to a closed and sealed position, wherein the ball  238  is seated within a chamfered portion  233  located in the conduit  224 . As assembled, the ball valve  232  is biased into a closed position against the chamfered portion  233  of the conduit  224 . 
     As dielectric enhancement fluid is introduced into the injection plug  220 , the fluid pressure causes the ball  238  to overcome the spring force and compress the spring  236 , thereby causing the ball valve  232  to open and allow dielectric enhancement fluid to enter the injection port  14  of the injection elbow ( 10  of FIG.  1 ). When the flow of dielectric enhancement fluid ceases, the spring  236  biases the ball  238  of the ball valve  232  to the closed position, thereby blocking the escape of dielectric enhancement fluid and any potential pathway that may be created. 
     The valve actuator assembly  234  is rotatably disposed within the injection plug  220  and allows the ball valve  232  to be manually opened to permit the removal of gas or fluid from the injection elbow  10 . The valve actuator assembly  234  includes a paddle mechanism  240  with an upper paddle  242  and a lower paddle  244 . The upper paddle  242  is connected to the lower paddle  244  by a shaft  246 . The upper paddle  242  is suitably orientated at a 90° angle relative to the lower paddle  244  and is located such that the lower paddle  244  rests against the plunger  231 , which is positioned next to the ball  238  of the ball valve  232 . As the upper paddle  242  is rotated, the lower paddle  244  is urged against the plunger  231  and the ball  238  of the ball valve  232 . As the lower paddle  244  is urged against the ball  238 , the ball compresses the spring  236  to open the ball valve  232 , thereby allowing fluidic communication from the injection elbow ( 10  of FIG. 1) into the conduit  224 . 
     In operation, dielectric enhancement fluid is injected through the conduit  224  of the injection plug  220  and into the injection elbow  10 . The spring  236  of the ball valve  232  is compressed by utilizing the fluid pressure of the dielectric enhancement fluid, thereby urging the ball  238  against the spring  236 . After introduction of the dielectric enhancement fluid into the injection elbow  10  is completed, the ball valve  232  is displaced into the closed position by the spring  236 . Finally, the upper paddle  242  is employed anytime the need arises for flow to move in the reverse direction of the valve&#39;s bias. The paddle can be operated such that the lower paddle  244  is urged against the ball  238  to open the ball valve  232  and allow for the removal of any air gas or fluids therein as required. At the end of the injection, the connecting tubing  280  is optionally removed, and the injection plug is optionally left in place forming a permanent barrier between the conductor and the ground plane. 
     Referring to FIG. 4, an injection plug  320  formed in accordance with another embodiment of the present invention will now be described in greater detail. The injection plug  320  illustrated in FIG. 4 is configured in a manner similar to the embodiment depicted in FIG.  3 . For instance, the injection plug  320  includes an elongated nozzle  350 , ball valve assembly  332 , and a conduit  324 . As depicted in FIG. 4, the conduit  324  is configured to allow fluidic communication between a supply source  380  and an opening  381  positioned near the end of the nozzle  350 . The injection plug  320  of the present embodiment also includes a spring bias ball valve assembly  332 . In one embodiment, the nozzle  350  is selectively fastened to one end of the injection plug  320 . As shown in FIG. 4, the nozzle  350  may be attached to the injection plug  320  by the use of a connector  351  such as a latch, threaded connection, or the like. In yet another embodiment, the injection plug  320  comprises a rod  352  that is formed and configured to be slidedly inserted into the nozzle  350  when the nozzle  350  is attached to the injection plunger  320 . 
     The ball valve assembly  332  includes a spring  336  and a ball  338 . The spring  336  normally biases the ball  338  against a chamfered portion  333  formed within the nozzle  350 , thereby displacing the ball valve assembly  332  into a closed position. In operation, when the injection nozzle is fully threaded, the rod  352  extends through the nozzle  350  and displaces the ball from its seat allowing fluid, gasses or air to move in either direction. Upon completion of the injection process, the nozzle  350  can be detached from the plug  320 , thereby withdrawing the inner rod  352  from the nozzle  350 . The removal of the inner rod  352  from the nozzle  350  allows the spring  336  to move the ball  338  toward the chamfered portion  333 , thereby preventing fluidic communication from the opening  381  into the nozzle  350 . 
     In one embodiment, the nozzle  350  is threadably connected to the body of the injection plug  320  to permit the ball valve assembly  332  to be manually actuated between an open and a closed position by the attachment and detachment of the nozzle  350 . In the open position, the nozzle  350  is rotated inward for further engagement with the injection plug  320 . With the nozzle  350  in the open position, the ball  338  is urged against the rod  352  thereby compressing the spring  336  and opening the ball valve  332 . The embodiments of FIGS. 3 and 4 depict two devices suitable for creating a physical barrier between the conductive core  4  and the ground plane. However, it should be apparent that a variety of gate valves or check valves, actuated manually, electronically, hydraulically, or pneumatically are also within the scope of the described embodiments of the present invention. 
     Referring now to FIG. 5, another embodiment of an injection plug  420  formed in accordance with the present invention will now be described in greater detail. The injection plug  420  of FIG. 5 is constructed in a manner similar to the injection plug  220  depicted in FIG.  1 A. For instance, the injection plug  420  comprises a stem portion  422 , a conduit  424  internal to the injection plug  420 , and a supply source  480 . In addition, the injection plug  420  depicted in FIG. 5 also comprises a cap  462 , wherein the cap  462  is positioned at the end of the stem portion  422  and affixed to the stem  422  by a friction type fastener or the like. As described below, the cap  462  is operable to create a barrier in the injection port of an elbow when the injection plug is removed from the injection port. The cap may be made of any flexible material such as rubber or the like. Also shown in FIG. 5, the stem portion  422  also comprises at least one aperture positioned on at least one side of the stem portion  422  for allowing fluidic communication between the conduit  424  and the environment external to the plug  420 . 
     Referring now to FIGS. 1A and 5, the operation of the embodiment shown in FIG. 5 will now be described. In one embodiment, the aperture  464  is positioned near the stem portion  422 , such that when the stem portion  422  of the plug  420  is inserted into an injection port  14  of an injection elbow  10 , the aperture  464  provides for fluidic communication between the conduit  424  of the plug  420  and the chamber  12  of the elbow  10 . Once the stem portion  422  is fully inserted into the injection port  14 , a fluid may be injected into the injection port  14  via the conduit  424 . Once the injection is complete, the injection plug  420  is withdrawn partially from the injection port  14 . In the removal of the injection plug  420 , the cap  464  rests against the surface of the fluid chamber  12  and becomes lodged in the injection port  14 , thereby preventing fluidic communication between the fluid chamber  12  and the injection port  14 . 
     In another embodiment, the cap  462  is affixed to the end  460  of the stem portion  422  by a threaded connection. In the operation of this embodiment, when the injection plug  420  is withdrawn from the injection port  14 , the cap  462  either pulls off or is unthreaded so that the cap  462  remains in the injection port  14  of the elbow  10 . Like the above-described embodiment, cap  462  is configured with a flexible material, such that, when the injection plug  420  is removed from the injection port  14 , the cap  462  is lodged in the injection port  14 , thereby preventing fluidic communication between the fluid chamber  12  and the environment external to the elbow  10 . 
     While the preferred embodiment of the invention has been illustrated and described, it will be appreciated that various changes can be made therein without departing from the scope of the present invention.