A power cable is an electrical cable, an assembly of one or more electrical conductors, usually held together with an overall sheath. The assembly is used for transmission of electrical power. Power cables may be installed as permanent wiring within buildings, buried in the ground, run overhead, or exposed. Power cables that are bundled inside thermoplastic sheathing and that are intended to be run inside a building are known as NM-B (nonmetallic sheathed building cable).
Flexible power cables are used for portable devices, mobile tools, and machinery.
The first power distribution system developed by Thomas Edison in 1882 in New York City used copper rods, wrapped in jute and placed in rigid pipes filled with a bituminous compound. Although vulcanized rubber had been patented by Charles Goodyear in 1844, it was not applied to cable insulation until the 1880s, when it was used for lighting circuits. Rubber-insulated cable was used for 11,000-volt circuits in 1897 installed for the Niagara Falls power project.
Mass-impregnated paper-insulated medium voltage cables were commercially practical by 1895. During World War II several varieties of synthetic rubber and polyethylene insulation were applied to cables.
Typical residential and office construction in North America has gone through several technologies:
Early bare and cloth-covered wires installed with staples
Knob and tube wiring, 1880s-1930s, using asphalt-saturated cloth or later rubber insulation
Armored cable, known by the genericized trademark "BX" - flexible steel sheath with two cloth-covered, rubber-insulated conductors - introduced in 1906 but more expensive than open single conductors
Rubber-insulated wires with jackets of woven cotton cloth (usually impregnated with tar), waxed paper filler - introduced in 1922
Modern two or three-wire+ground PVC-insulated cable (e.g., NM-B), produced by such brands as Romex®
Aluminum wire was used in the 1960s and 1970s as a cheap replacement for copper and is still used today, but this is now considered unsafe, without proper installation, due to corrosion, softness and creeping of connection.
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Piscataway2024
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