Abstract: Different from overhead transmission lines, the power cables have large shunt capacitance, which leads to large charge capacitive current and high open end overvoltage under no-load operation condition. Based on the positive sequence model for power cables, a steady state analytical method is proposed to study the ultimate transmission length of power cables. The method proposed in this paper can calculate the ultimate length of lossy cables with different end voltages. The study shows that the open end overvoltage has little limitation on the cables with a length under 200 km. The open end overvoltage is less than 1% for the cable with a length under 40 km, which is in good agreement with the field test. The capacitive charge current is the bottleneck for limiting the transmission length of cables. However, the calculation results show that when the compensation ratio is set at 0.3, a 100-km long cable, much longer than the 60-km long cable now in common use, can have a power factor of 0.94, indicating that the 100-km super-long cable is theoretically feasible.

Key words: power cable, positive sequence model, ultimate length, shunt reactor compensation