Digital simulation of faulted e.h.v. transmission lines with particular reference to very-high-speed protection

Increasing demands for ultralow fault clearance times in electrical power systems require that measurements be made from information derived from power lines during a very short interval after fault inception. For research and development purposes, the precise nature of this information is required, and in this paper modern transmission-line theory is used to predict the fault-transient behaviour of multiconductor overhead lines to a greater degree of accuracy than has hitherto been possible. The nonlinear nature of simulating fault-transient phenomena has been overcome, and it is shown that even on lines which have traditionally been regarded as electrically short, very severe transient conditions can exist. The necessity for an accurate representation of the frequency variance of line parameters is established, and the various factors which influence fault transient phenomena are considered. The paper concludes with a presentation of the results of studies relating to a very long transmission line.