From Encyclopedia Jr, free information reference for Kids
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For other uses, see Cable (disambiguation).
6" or 15cm outside diameter, oil-cooled cables, traversing the
Grand Coulee Dam throughout. These cables are connected to powerful pumps that pump the oil through them while in operation. Safety switches turn off the oil flow in the event of a leak, in order to limit the effects of a hydrocarbon fire.
A cable is 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 bare, covered or insulated. Combination cables may contain both electrical wires and optical fibers. 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 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.
[edit] Fire protection
[edit] Cables as a fire hazard
Power and control
cables used in a
firestop test assembly. The greater the copper conductor cross sectional area, the more heat is conducted to the unexposed side of the assembly.
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.
[edit] 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[1].
[edit] Interference Protection
In applications powering sensitive electronics, keeping unwanted EMI/RFI from entering circuits is important. This can be accomplished passively with shielding along the length of the cable or by running the cable in an enclosure separate from any other wires which may induct noise. It can also be actively achieved by use of a choke designed to restrict the cables' ability to conduct certain frequencies.
[edit] Types of cable
Cables can be sorted into several categories and types. Generally it can by sorted into two main groups:
[edit] Application
- Wire rope (wire cable)
- Computer cable
- Communications cable
- Mechanical cable
[edit] Cable type
Basic cable types are as follows:
[edit] Basic
- Coaxial cable
- Multicore cable (consist of more as one wire and is covered by cable jacket)
- Optical fiber
- Ribbon cable
- Single cable (from time to time this name is used for wire)
[edit] Construction
Based on construction and cable properties it can be sorted into following:
- Insulated cable
- Mineral-insulated copper-clad cable
- Twinax cable
- Twisted pair cable
- Shielded cable
[edit] Special
- Arresting cable
- Bowden cable
- Heliax cable
[edit] See also
- Communications cable
- Cable length
- Circuit integrity
- Cable modem
- Cable spaghetti
- Cable television
- DOCSIS
- Extension cable
- MF
- Rope
- Submarine communications cable
- Submarine power cable
[edit] External links
