This article is about electric power conductors. For portable equipment, see power cord.
A power cable is 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.
Flexible power cables are used for portable devices, mobile tools and machinery.
Power cable History
Early telegraph systems used the first forms of electrical cabling, transmitting tiny amounts of power. Gutta-percha insulation used on the first submarine cables was, however, unsuitable for building wiring use since it deteriorated rapidly when exposed to air.
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.

Construction
Modern power cables come in a variety of sizes, materials, and types, each particularly adapted to its uses. Large single insulated conductors are also sometimes called power cables in the industry.
Cables consist of three major components: conductors, insulation, protective jacket. The makeup of individual cables varies according to application. The construction and material are determined by three main factors:
※ Working voltage, determining the thickness of the insulation;
※ Current-carrying capacity, determining the cross-sectional size of the conductor(s);
※ Environmental conditions such as temperature, water, chemical or sunlight exposure, and mechanical impact, determining the form and composition of the outer cable jacket.
Cables for direct burial or for exposed installations may also include metal armor in the form of wires spiralled around the cable, or a corrugated tape wrapped around it. The armor may be made of steel or aluminum, and although connected to earth ground is not intended to carry current during normal operation.
Power cables use stranded copper or aluminum conductors, although small power cables may use solid conductors (For a detailed discussion on copper cables, see: Copper wire and cable.).
The cable may include uninsulated conductors used for the circuit neutral or for ground (earth) connection.
The overall assembly may be round or flat. Non-conducting filler strands may be added to the assembly to maintain its shape. Special purpose power cables for overhead or vertical use may have additional elements such as steel or Kevlar structural supports.
Some power cables for outdoor overhead use may have no overall sheath. Other cables may have a plastic or metal sheath enclosing all the conductors. The materials for the sheath will be selected for resistance to water, oil, sunlight, underground conditions, chemical vapors, impact, or high temperatures. In nuclear industry applications the cable may have special requirements for ionizing radiation resistance. Cable materials may be specified not to produce large amounts of smoke if burned. Cables intended for underground use or direct burial in earth will have heavy plastic or metal, most often lead sheaths, or may require special direct-buried construction. When cables must run where exposed to mechanical impact damage, they may protected with flexible steel tape or wire armor, which may also be covered by a water resistant jacket.
The information is taken from Wikipedia, the free encyclopedia. For more wire and canle knowledge, Please visit www.qscable.com and www.huadongcable.com.