Abstract:
An insulative body adapted to be deformed into contact with a plurality of loadbreak elbow connectors secured to a transformer or other electrical apparatus during repair or replacement, providing safe and secure access for a linesman. The body enshrouds a volume surrounding a plurality of loadbreak elbow connectors with a form-fitting structure adapted to deform into contact with the plurality of loadbreak elbow connectors when an external force is used to place the cover. Collar portions defining retaining structure are adapted to retain the cover in place until an external force is applied to remove the cover.

Description:
FIELD OF THE INVENTION 
     The invention relates to protective barrier structures for electrical connectors particularly in the transmission of electrical power through pad-mounted electrical equipment. More particularly, the invention relates to devices and associated operating procedures for assuring the safety of working personnel when performing repairs upon energized pad-mounted electrical equipment by reducing the risk of accidental arcing and resultant flash-related injuries to personnel and damage to equipment. 
     BACKGROUND OF THE INVENTION 
     An electrical distribution system typically includes distribution lines or feeders that extend out from a substation transformer. The substation transformer is typically connected to a generator via electrical transmission lines. Along the path of a feeder, one or more distribution transformers may be provided to further step down the distribution voltage for a commercial or residential customer. The distribution voltage range may be from 5 through 46 kV, for example. Various connectors are used throughout the distribution system. In particular, the primary side of a distribution transformer typically includes a transformer bushing to which a bushing insert is connected. In turn, an elbow connector, for example, may be removably coupled to the bushing insert. The distribution feeder is also fixed to the other end of the elbow connector. Of course, other types of connectors are also used in a typical electrical power distribution system. For example, the connectors may be considered as including other types of removable connectors, as well as fixed splices and terminations. Large commercial users may also have a need for such high voltage connectors. 
     The prior art includes the use of insulative blankets to protect lineman from active elbow connectors. Clips have been used to temporarily secure the blankets in place. The blankets tend to be large and bulky and typically prevent the lineman from visual access to other portions of the electrical equipment. The blanket may be easily dislodged if the clips are knocked off or otherwise inadvertently removed, resulting in loss of protection for the linemen. 
     There remains a need for safety devices and associated operating procedures to enable linemen to work inside energized pad-mounted electrical equipment with a substantially reduced risk of creating a flash situation. 
     SUMMARY OF THE INVENTION 
     The present invention addresses the above concern for worker safety by providing a specially tailored flash-preventing safety shield that can be readily inserted in place prior to work at the access side of energized electrical equipment. The safety shield takes the form of a preformed electrically insulated cover including locating and securing structure that slides over one or more loadbreak electrical connectors, such as elbows. The securing structure serves to locate the shield in an orientation that protects against flashes and also serves to retain the shield in place, preferably including a friction fit in some areas. In one preferred embodiment, the shield may take a generally inverted L-shape with four depressions to one edge of the shield and with the remaining portion of the shield being of sufficient size to cover the adjacent portions of the elbow connectors at which a flash is most likely to occur. The shield also may include raised portions that provide added protection so that the lineman&#39;s tools cannot contact surfaces of most commonly used elbow connectors. In one embodiment, the shield is formed from a resilient material having a thickness sufficient to provide adequate insulative protection for the voltage levels encountered in typical transformers. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the accompanying drawings which form part of the specification and wherein like numerals and letters refer to like parts wherever they occur. 
         FIG. 1  is a perspective illustration of a transformer and plurality of elbow connectors secured thereto. 
         FIG. 2  is a cross-sectional view taken through an elbow connector of the prior art. 
         FIG. 3  is a perspective illustration of an embodiment of a loadbreak elbow connector cover in accordance with the present invention 
         FIG. 4  is a side view of the elbow connector cover of  FIG. 3  attached to an elbow connector 
         FIG. 5  is a top view of the elbow connector cover of  FIG. 3   
         FIG. 6  is another side view of the elbow connector cover of  FIG. 3 . 
         FIG. 7  is another side view of the elbow connector cover of  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. Like numbers refer to like elements throughout, and prime notation is used to indicate similar elements in alternate embodiments. 
     In a residential application, the interior of a transformer includes one side where the transformer windings are encased in oil and a second “access side” where the line connections are made for connecting the wires from the transformer to the several (e.g., 3 to 8) houses being served by the transformer. The transformer side and the access side are separated by a “transformer face” that extends vertically. When a lineman opens a transformer for access, he typically sees three secondary bushings at 120V/240V and two or more primary bushings at a voltage in the range of 7,000V to 25,000, usually about 13,000V. Each of the secondary bushings supports a standard connector at which the wires are connected for running to the houses. 
     When it becomes necessary to service the transformer (for example, to remove and replace a wire connected to one of the connector bars) it is important that proper safety precautions are used. First, the lineman should wear rubber gloves. Second, the lineman should secure insulative blankets over the connector bars that are not being accessed. At this point, according to prior art practices, the worker is ready to access connector bar bolts and/or elbows for replacement or repair. The worker has to be very careful not to allow conductive tools to contact the transformer face. For example, when a wrench contacts the transformer face, a “flash” situation results. A flash produces a bright light that can damage the worker&#39;s eyes, can damage the tools in use, can damage the bushing and can otherwise damage the transformer to the point where it may have to be removed from use. 
       FIG. 1  illustrates a plurality of elbow connectors  20  electrically coupled to transformer  22 . In this example, transformer  22  includes four terminals with three elbow connectors  20  being shown. Transformer  22  can assume a variety of sizes and shapes and the present invention is not limited to any particular transformer  22  design. One embodiment of electrical elbow connector  20  is initially described. As will be appreciated by those skilled in the art, the elbow connector  20  is but one example of an electrical connector, such as for high voltage power distribution applications, comprising a connector body having first and second intersecting passageways therethrough. That is, the present invention may advantageously be applicable to other connector types (T-shaped, etc.), as well. 
     Referring to  FIG. 2 , an electrical elbow connector  20  is initially described. As will be appreciated by those skilled in the art, elbow connector  20  is but one example of an electrical connector, such as for high voltage power distribution applications, comprising a connector body  24  having first and second intersecting passageways  26 ,  28  therethrough. Elbow connector  20  includes a conductive bushing stud  30  conductively coupled via probe tip  32 , probe  34  and conductor  36  to conductor  38  within insulated cable  40 . Connector body  24  defines an insulating layer that covers the electrically conductive components of elbow  20 . Elbow connector  20  also includes ground wire  42 , capacitive voltage cap  44  and pulling eye  46 . Body  24  comprise one or more electrically insulative layers as described below. 
       FIG. 3  is a perspective illustration of an elbow cover  50  in accordance with the present invention. Elbow cover  50  includes a plurality of sections as  50   a ,  50   b ,  50   c ,  50   d . Elbow cover  50  defines an external side  52  and an internal side  54  and a pair of elbow-engaging collar portions  60 ,  62 . A central portion  64  is provided between collar portions  60 ,  62 . Depending on the particular application, central portion  64  may engage elbow  20  or may be offset from contact with elbow  20 . 
       FIG. 3  shows the elbow cover  50  prior to be secured over a plurality of elbow connectors  20 . In comparison,  FIG. 4  is a side view and shows the elbow cover  50  in positive position after being secured over elbow connectors  20 . As shown, elbow-engaging collar portions  60 ,  62  engage corresponding portions of elbow connectors  20 . 
     Referring to  FIG. 5 , upper collar portions  60  include a pair of inner collar portions, designated  60   a  and  60   b  and a pair of outer collar portions, designated  60   c  and  60   d . Outer collar portions  60   c  and  60   d  are sized to engage a greater extent of elbow connectors  20 . 
     Referring to  FIGS. 6 and 7 , lower collar portions  62  include a pair of inner collar portions, designated  62   a  and  62   b  and a pair of outer collar portions, designated  62   c  and  62   d . Outer collar portions  62   c  and  62   d  are sized to engage a greater extent of elbow connectors  20 . Outer collar portions  62   c  and  62   d  define skirts and are slightly splayed to serve as ramps or cam surfaces that spread apart the resilient cover  50  to accommodate the plurality of elbow connectors  20 . 
     In operation, the inner surfaces of the cover  50  are designed to contact the plurality of elbow connectors  20  as the lineman pushes cover  50  into place. The resiliency and memory of the material forming cover  50  permits the cover to tightly overlie the elbow connectors  20  during repair operations, resulting in a less bulky cover that is positively positioned. The reduced bulk and improved fit of elbow cover  50  gives the lineman an increased work zone. 
     In use of a preferred embodiment of the present invention, elbow-engaging collar portions  60 ,  62  are sized to engage a plurality of elbow connectors  20 . In a preferred embodiment, collar portions  60 ,  62  are sufficiently flexible so as to deform against the elbow connectors  20  and be retained against elbow connectors  20  in a form-fitting manner. Collar portions  60 ,  62 , in the preferred embodiment of the present invention are defined by generally semi-circular cross sections. Similarly, collar portions  60 ,  62  are deformed during a removal process when an external force is used to remove the cover  50  from the plurality of elbow connectors  20 . 
     The material chosen for elbow cover  50  should have low electrical conductivity, low surface porosity (in particular, the surface should be highly hydrophobic) and high physical robustness (including both strength and abrasion resistance). High molecular density polymers are believed to be advantageous. For example, elbow cover  50  may include polyvinyliden fluoride (PDVF), polytetrafluoroethylene (PTFE), fluorinated ethylene-propylene (FEP) and other known materials. A variety of manufacturing techniques such as molding and vacuum forming may be utilized for elbow cover  50 . One preferred method is to vacuum form elbow cover  50  from sheet stock. 
     Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.