Cables

A cable is one, two or more wires or optical fibers bound together, typically in a common protective jacket or sheath. The individual wires or fibers inside the jacket may be covered or insulated. Combination cables may contain both electrical wires and optical fibers. more...

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Electrical wire is usually copper because of its excellent conductivity, but aluminium is sometimes used because it costs less.

Electrical cables may be made more flexible by stranding the wires. In this process, smaller individual wires are twisted or braided together to produce larger wires that are more flexible than solid wires of similar size. Bunching small wires before concentric stranding adds the most flexibility. A thin coat of a specific material (usually tin, but it could be silver, gold and another materials and of course the wire can be unplated - with no coating material) on the individual wires provides lubrication for longest life. Tight lays during stranding makes the cable extensible (CBA - as in telephone handset cords).

Cables can be securely fastened and organized, such as using cable trees with the aid of cable ties. "Octopus cable" is a generic term for a cable that splits into several parts.

In the 19th century and early 20th century, cable was often insulated using cloth, rubber and even paper. Plastic materials are generally used today, except for high reliability power cables. There are four types of plastic insulation used in telecommunications cables today: solid, cellular, foam skin and skin-foam-skin.

In 2004 some of the leading global producers of cable products included Draka, General Cable, Nexans, Prysmian,Hesfibel Co Sumitomo Electric Industries, Furukawa Electric, Hitachi Cable, Southwire, Marmon Group, LS Cable, LEONI, Fujikura, Tyco, Walsin Lihwa and Wilms Group.

Fire protection

Cables as a fire hazard

In construction, sometimes the cable jacketing is seen as a potential source of fuel for a fire. To limit the spread of fire along cable jacketing, one may use cable coating materials or one may use cables with jacketing that is inherently fire retardant. Teck cable or metal clad cables, may have exterior organic jacketing, which is often stripped off by electricians in order to reduce the fuel source for accidental fires. In Europe in particular, it is often customary to place inorganic wraps and boxes around cables in order to safeguard the adjacent areas from the potential fire threat associated with unprotected cable jacketing. All such mitigation methods are passive fire protection items subject to stringent bounding.

Keeping critical cables operational during a fire

Circuit integrity for cables is also established by using either inherently fire resistant cables, such as Mineral-insulated copper-clad cables, or by using boxes made of proprietary insulations, such as calcium silicate, vermiculite or perlite, intumescent and/or endothermic coatings or ceramic fibre or rockwool wraps for fireproofing purposes. Electrical circuits that may have to be kept operational during an accidental building fire include, but are not limited to emergency power circuits, such as those that power exit signs in a building, power circuits for operating rooms in a hospital, or the wiring that connects control rooms and nuclear reactors. All such mitigation methods are passive fire protection items subject to stringent bounding. The toughest of test methods known in the industry are those mandated by the US Nuclear Regulatory Commission, which came about as a result of the Thermo-lag scandal.

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