Computation of horizontal three-phase line capacitances

The author shows that it is possible to determine the horizontal three-phase line capacitance with the consideration of influences caused by the earth surface and ground wire. The computation results show that the increase in capacitance value caused by the ground wire is very small and can be neglected practically. For horizontal three-phase lines the capacitance of centre phase is much higher than the outer phases. This is very important and useful for the studies of corona, electric field, electrostatic imbalance of extra-high and ultra-high voltage transmission lines.