Included in this category are all types of terminations, splices, cablefittings, wire markers, terminal blocks, pin and sleeve connectors, control and coax connectors, and cable supports.
Electrical systems essentially are networks of conductors that distribute power to various locations, interconnect control and instrumentation equipment, provide the physical means by which communications and signals are transmitted, and are the pathways by which data is transferred from the workstation PC to other computers, peripherals. or the mainframe. Without a steady, reliable conductor system, the use of electricity on a large scale would be impossible. That is why the splicing, termination, support, and identification of conductors are so vital.
600V lugs and terminations
Lugs and other devices used to terminate wire vary greatly according to conductor size and system voltage level. In 600V systems, terminating, taping, and splicing of cable require simpler techniques than those for medium voltage systems. Mechanically bolted connections, such as a split bolt connector, serve a variety of needs. The mechanical devices, however, are being challenged by crimping types. The specific pattern of the crimped indentations, tools used, etc., tends to vary.
Larger conductor lugs have thick flanges that are predrilled for one or more bolts. Connectors used for building and control wire sizes are fork- or ring-type, generally with an insulated sleeve. Twist-on wire connectors are widely employed for joining or splicing two or more wires. Crimped insulated inline splices and many similar types of connecting devices are suitable for use in cramped enclosures and boxes, or in cases where appearance of the wires and their training is important.
Control systems require extensive interconnection of circuitry, and terminal blocks are widely used in these applications. They act as convenient tie points while providing convenient locations for accessing the wiring for troubleshooting. Terminal blocks come in many modular sizes, with some capable of being DEN rail mounted. Wire identification strips are standard, with covers and other accessories available. Specialized terminal blocks are for thermocouple circuits and power feeders.
terminations and splices
Terminators in medium voltage systems are constructed with materials specifically designed to minimize voltage stress concentrations and subsequent cable failure. Potheads have long been used for making a transition from single- or multiconductor insulated cable to bare or covered overhead poleline conductors, or to busbars of distribution equipment. Proper penciling of the insulation and taping is required. A potting compound seals the finished termination from the elements.
Variations of this technique have been developed using specialized insulation kits. Preassembled terminators permit properly prepared cable to be terminated by slipping various components in place, reducing (but not eliminating) the skill needed to complete the installation. Another variation involves the crimping of a lug onto the cable end, and then applying heat-shrink components to provide the proper stress distribution for the insulation.
Power plugs are available for all voltages, from medium voltage ones used with power shovel feeder cable to plugs for welding receptacles, to multiconductor ones used in low voltage control and instrumentation circuits. They all are pin-and-sleeve type. Configurations vary according to circuits requirements.
Wiring identification and support
Identification of wires, especially in complex control and data circuits, is essential. Many types of wire markers are available for this purpose, from wraparound preprinted letter and number tapes to computer-generated numbering systems.
Plastic ties are used for support, and basket-weave elastomer fitting, and plastic spirals are used for strain relief.