Thus, to protect the insulation from too much heat, the current through the conductor must be maintained below a certain value. If the conductor is insulated, the heat generated in the conductor is not so readily removed as it would be if the conductor were not insulated.
The temperature of the wire rises until the heat radiated, or otherwise dissipated, is equal to the heat generated by the passage of current through the line. When current is drawn through the conductor, heat is generated.A compromise is generally reached whereby the voltage variation at the load is within tolerable limits and the weight of line conductors is not excessive. A reduction in load current lowers the amount of power being transmitted, whereas a reduction in line resistance increases the size and weight of conductors required. The obvious remedy is to reduce either current or resistance. A wide variation in the IR drop in the line causes poor voltage regulation at the load. If the source maintains a constant voltage at the input to the lines, any variation in the load on the line causes a variation in line current and a consequent variation in the IR drop in the line.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.Several factors must be considered in selecting the size of wire for transmitting and distributing electric power.
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