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By estimating the temperature of the cables, the safe long-term current-carrying capacity of the cables can be calculated. J. H. Neher and M. H. McGrath were two electrical engineers who wrote a paper in 1957 about how to calculate the capacity of current (ampacity) of cables. [1]
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 ...
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).
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.
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.
The higher current results in greater resistive losses in the cabling. 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 ...
Conductors installed so that air can freely move over them can be rated to carry more current than conductors run inside a conduit or buried underground. High ambient temperature may reduce the current rating of a conductor. Cables run in wet or oily locations may carry a lower temperature rating than in a dry installation. A lower rating will ...
The following are nominal current ratings for copper conductors; long runs may require thicker wires to minimize voltage drop. White: 14 AWG wire (2.08 mm 2) for 15-amp circuits Yellow: 12 AWG wire (3.31 mm 2) for 20-amp circuits Orange: 10 AWG wire (5.26 mm 2) for 30-amp circuits