Computing overhead line parameters

This study focuses on the computation of line constants at the power line frequencies of 50 and 60 Hz. At this frequency range, computer methods and handbook formulas give virtually identical positive-sequence impedances, with the exception of overhead lines with ground wires. A study by H. Dommel (1985) confirmed that the positive-sequence impedance given by the two methods are usually within a small fraction of 1%, a difference that is negligible compared to the uncertainties in the physical parameters. But in cases where ground wires are present, the study showed a substantial difference between the results of handbook formulas and those of computer programs. The recent availability of graphical user interfaces has prompted the development of line-constraints programs that use interactive graphics. One such program, called the ASPEN Line Constants Program, is described briefly. This description illustrates the typical inputs to a line constants program.<>