Zero-Sequence Current Distribution Along Transmission Lines

The zero-sequence current distribution among ground wires and the ground-return path of overhead transmission lines is subject to change in the vicinity of a ground fault and the feeding point. This paper introduces the concepts used in connection with the end-effect phenomena of transmission lines and describes the necessity for solving the end-effect current distribution. After dealing with the influential factors and basic assumptions, it describes a new calculation method which can be extended to develop generalized equations. The procedures to be followed in the case of ground faults supplied from either one or both sides are detailed. A summary of field tests is also included. The deviations between the measured and the computed values are found to be less than 15 percent. Several cases were studied to investigate the effect of factors, such as ground-wire material, tower-footing resistance, soil resistivity, and distance between feeding point and fault.