There is a need in several industries for splicing together two or more insulated cables containing solid or stranded wire. One such industry is the power transmission industry, which employs a myriad array of types of cables for different distribution needs. One such cable type used for low voltage distribution lines is secondary cable. As used herein “secondary cable” is intended to include cables configured to operate at about 600 volts or less and to be deployed on a low voltage side of a distribution transformer in an electrical distribution system. The secondary cable comprises one or more conductors encased in some form of insulation. In contrast, as used herein, “primary cable” is intended to include cables configured to operate at or above 8 kV and to be deployed on a high voltage side of a distribution transformer in an electrical distribution system. The secondary cable comprises one or more conductors encased in some form of insulation. Primary cable includes both insulating and semi-conductive layers having the following construction: conductor, semi-conducting material, insulating material, semi-conductive layer, metallic shield.
Splicing secondary cables together or secondary cables to a multi-way joint, such as a crab joint, requires a metallic connector to join two conductors together and an insulation system to prevent energized conductors from shorting to adjacent cables or to ground or from creating stray voltages to surrounding objects. In practice, the insulation system of a secondary splice should be approximately 10 inches in length to cover the connector and provide sufficient overlap of the cable ends. It is further desirable that the insulation system have the following properties: provide insulation over any exposed conductor and connector; provide a water-tight seal between itself and underlying cable insulation such that environmental water cannot reach a spliced cable conductor or a metallic connector; be sufficiently tough to prevent typical external abrasion from damaging the insulating or sealing characteristics of a splice; conduct heat generated in a conductor/connector to the external environment sufficiently to permit a completed splice to operate at or below the temperature of the bulk cable; and, be sufficiently easy to install by a splicer to minimize chances for installation errors.
There are many prior art insulation systems methods currently available. Among these are insulating tape, interference fit push on, heat shrinkable materials, and cold shrinkable materials. The corresponding method for creating a splice using each type of insulating system is described hereinbelow.
After two cables are joined with a connector, electrical tape may be layered over the connector and a portion of the cable insulation. Drawbacks to employing electrical tape and its splicing method include the large amount of time necessary to construct the splice and the necessary high skill level of the splicer to construct an adequate splice.
To perform a splice with an interference fit push-on insulation system, prior to connecting the cables with a connector, a push-on housing is stored onto one of the cables. After a connector is installed, the push-on housing is positioned over the connector and cable ends. Drawbacks to employing this method include a large installation force necessary to store and position the housing. It is also difficult to seal the splice if there are any protrusions such as phase markers or dips in the cable insulation surface from damage.
To perform a splice with heat shrinkable materials, prior to connecting the cables with a connector, an expanded heat shrinkable tube or tubes is stored onto one of the cables. After a connector is installed, the heat shrinkable tube is slid back over the connector and cable ends. With the application of heat, the tube is reduced in size until it shrinks completely in place. To provide adequate sealing to the cable ends, the insulating tube is provided with an adhesive on the inside that is activated by applied heat. Drawbacks to this method include the use of a potentially dangerous torch. High skill levels are required to ensure that the heat shrinkable tube(s) uniformly and adequately shrink and that sufficient heat is used to activate a sealing materials but not too large an amount of heat to damage any materials or the cable insulation.
To perform a splice with cold shrinkable materials, prior to connecting the cables with a connector, an expanded cold shrinkable tube is stored onto one of the cables. After a connector is installed, the cold shrinkable tube is slid back over the connector and cable ends. A support core is removed from one end (or removed from each end in the case of a two-piece support core), thereby permitting the insulating housing to constrict over the connector and cable ends. The support tube(s) may be solid-type cores, spiral cores, or friable cores. Again, a sealing material is needed to provide a proper environmental sealing. Sealing materials are typically of a putty consistency such a butyl. The putty is usually applied to the cable insulation ends prior to pulling the expanded tube into position. As a result of foreseeable workmanship mistakes, it is desirable to pre-install the putty under the removable core. Unfortunately, maintaining the position of the putty during core removal is problematic. Another drawback to employing cold shrinkable materials using existing installation methods includes the need to use long lengths of support cores, which may be time consuming for a splicer to remove or may create an ergonomic issue when trying to unwind such long support cores.
When spiral cores are employed in connection with cold shrinkable materials, as the core(s) is (are) removed, they must be unwound to prevent jamming. It is difficult to keep mastic (i.e., putty) in place if included under a pre-stretched cold shrinkable tube. Further, if mastic is supplied and installed separately, there is a high risk it would inadvertently be left out of the installation. Still further, spiral cores require the shrinkable tube to be expanded sufficiently to allow easy removal of the core. In designs that employ a central, non-removable support core and only short spiral cores on the ends, a workable method of removing heat from the connector is desirable, since there would be an air space left between the non-removed support core and the connector.
When solid cores are employed in connection with cold shrinkable materials, the cold shrinkable tube does not need to be expanded as much as the spiral support core, since the support core is pulled back from one or both ends (i.e., solid cores do not require as much clearance between the cable, connector, and inside diameter of the support core). Further, an auxiliary film needs to be installed between the shrinkable tube and the support core to aid in easy removal. A splicing method that employs solid cores lends itself to the application of pre-installed sealing mastic pre-installed. Unfortunately, the significantly long length of solid cores renders them difficult to remove if there is insufficient space in the splice compartment, even when a mylar release material is employed.
Accordingly, what would be desirable, but has not yet been provided, is a system and method for employing cold shrinkable materials for performing splices on secondary cables that overcome the deficiencies in the prior art described hereinabove.