Effect of magnetic induction in a steel-cored conductor on current distribution, resistance and power loss

The presence of a steel core in the commonly used aluminum conductor, steel reinforced (ACSR) on overhead transmission lines causes an increase in the AC resistance of the conductor, as a result of the magnetic induction in the core. This induction, which is higher with an odd number of aluminum layers, causes hysteresis and eddy current power losses in the steel, and a redistribution of current in the layers of aluminum wires. The effects of the total current in the conductor and the temperature of the steel core on the current distribution, the AC/DC resistance ratio and the power loss are determined for a Grackle conductor with three layers of aluminum wires. It is shown that the resistance ratio and the power loss can be significantly reduced at higher currents by careful design of the lay length (pitch) of each layer of aluminum wires.