Influence of High-Voltage Cable Conductor Structures on AC and DC Resistances

To meet increasing demands of high-voltage transmission systems for cable current-carrying capacity and operational efficiency, optimal design of conductor structures is crucial. In order to investigate the influence of conductor cross-section and the number of single wires on AC and DC resistance, a double-bridge method and a power method were used to measure DC and AC resistance of samples with different cross-sections and different numbers of single wires. Results showed that DC resistance decreased significantly with increasing conductor cross-section, consistent with the inverse relationship between resistance and cross-sectional area. AC resistance was found to increase with temperature, but growth tended to level off in large-cross-section conductors. This was because skin depth increased with resistivity, and variation in effective cross-sectional area partially offset the effect of rising resistivity. For the same cross-section, an increase in the number of single wires led to a slight decrease in DC resistance, mainly due to a reduction in work-hardening coefficient caused by compaction when wires became finer, thereby lowering DC resistance. When single wires were sufficiently thin, eddy-current losses within each wire were greatly reduced, and current distribution became more uniform. Consequently, at a temperature of 90 ℃, AC resistance exhibited a decreasing trend as the number of single wires increased.