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Overhead insulated cables are rarely used, usually for short distances (less than a kilometer). Insulated cables can be directly fastened to structures without insulating supports. An overhead line with bare conductors insulated by air is typically less costly than a cable with insulated conductors. A more common approach is "covered" line wire.
A three phase electric circuit terminated with a pothead Crossarms with two three phase electric circuits terminated with potheads. A pothead is a type of insulated electrical terminal used for transitioning between overhead line and underground high-voltage cable or for connecting overhead wiring to equipment like transformers. [1]
Overhead lines, like most electrified systems, require a greater capital expenditure when building the system than an equivalent non-electric system. While a unelectrified railway line requires only the grade, ballast, ties and rails, an overhead system also requires a complex system of support structures, lines, insulators, power-control ...
In North America, overhead distribution systems may be three phase, four wire, with a neutral conductor. Rural distribution system may have long runs of one phase conductor and a neutral. [17] In other countries or in extreme rural areas the neutral wire is connected to the ground to use that as a return (single-wire earth return).
For uninsulated cables (typically used in outdoor overhead installations), the tensile strength of the cable (as affected by temperature) is normally the limiting material property. The Neher–McGrath method is the electrical industry standard for calculating cable ampacity, most often employed via lookup in tables of precomputed results for ...
Phasor diagram showing 240 V delta and center-tapped phase (a–c) creating two 120 V pairs. Consider the low-voltage side of a 120/240 V high leg delta connected transformer, where the b phase is the high leg. The line-to-line voltage magnitudes are all the same: = = =.
The following home services are supported by discrete wiring systems: Information and communications Entertainment Energy management Security and safety Digital home health Aged and assisted living Intelligent lighting and power In new home construction, wiring for all electrical services can be installed before the walls are finished.
That creates a system whereby a city can best avoid lawsuits by adopting a single standard set of building code laws. This has led to the NEC becoming the de facto standard set of electrical requirements. [6] A licensed electrician will have spent years of apprenticeship studying and practicing the NEC requirements prior to obtaining their license.