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For systems such as underground power transmission cables, evaluation of the short-term over-load capacity of the cable system requires a detailed analysis of the cable's thermal environment and an evaluation of the commercial value of the lost service life due to excess temperature rise.
The current-carrying capacity, or ampacity, of overhead lines starts with the type of conductor used. The conductor choice determines its electrical resistance and other physical parameters for dynamic line rating (DLR).
In electrical engineering, Neher–McGrath is a method of estimating the steady-state temperature of electrical power cables for some commonly encountered configurations. By estimating the temperature of the cables, the safe long-term current-carrying capacity of the cables can be calculated.
Comparison of SWG (red), AWG (blue) and IEC 60228 (black) wire gauge sizes from 0.03 to 200 mm² to scale on a 1 mm grid – in the SVG file, hover over a size to highlight it. In engineering applications, it is often most convenient to describe a wire in terms of its cross-section area, rather than its diameter, because the cross section is directly proportional to its strength and weight ...
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.
A wire or cable has a voltage (to neutral) rating and a maximum conductor surface temperature rating. The amount of current a cable or wire can safely carry depends on the installation conditions. The international standard wire sizes are given in the IEC 60228 standard of the International Electrotechnical Commission.
Cable sizing must therefore consider maximum demand, voltage drop over the cable, and current-carrying capacity. Voltage drop is usually the main factor considered, but current-carrying capacity is as important when considering short, high-current runs such as between a battery bank and inverter.
Conductor sizes range from 12 mm 2 (#6 American wire gauge) to 750 mm 2 (1,590,000 circular mils area), with varying resistance and current-carrying capacity. For large conductors (more than a few centimetres in diameter), much of the current flow is concentrated near the surface due to the skin effect. The center of the conductor carries ...