However, large conductors are more expensive, heavier, and need more substantial support. The use of large conductors reduces the resistance and therefore the I2 R loss. Allowable power loss (I2 R loss) in the line represents electrical energy converted into heat.Wires must have sufficient mechanical strength to allow for service conditions.
Read more about ampacity correction here.Several factors must be considered in selecting the size of wire for transmitting and distributing electric power. If the temperature in increases, ampacity is reduced and if temperature falls, it is increased. If there is a spike in temperature or if it drops, a correction factor must be applied. If grouped or bundled or enclosed, the Amps running through a cable must be decreased to ensure heat dissipation.Īgain, ampacity ratings are based upon ambient temperatures. To avoid this damaging occurrence, heat must be dissipated outside the cable. If the heat exceeds the cable’s rating, the cable could fail, even possibly catching fire. As current moves through a conductor, heat is created. Each cable and its jacketing and insulation is rated for specific temperatures. This rating is the maximum allowable current that a conductor, its jacket and insulation can carry without compromising safety at ambient temperatures. Other organizations that supply ampacity tables include IEEE (Institute of Electrical and Electronics Engineers), which offers more than 3,000 ampacity tables for extruded dielectric power cables rated through 138 kV and laminar dielectric power cables rated through 500 kV. Most cable manufacturers provide ampacity tables on their websites. This rating has been determined by the NEC (National Electrical Code), which lists ampacity ratings for real-life installation examples. When selecting a cable, one must know its wire ampacity rating.
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