Study of occurrence of overvoltage along power transmission lines with acceptable end voltage

Abstract

For studies of insulation coordination at industrial frequency transmission line must be modelled with much more details than for other studies, like load flow and short circuit analyses. In other words, that usual representation of the transmission line by a single quadrupole Pi circuit is not applicable. In fact, all of the three-phase conductors must be analyzed separately though the determination of individual voltage profile for several conditions of load. This is so because it is possible that voltage to ground of each conductor presents itself as satisfactory at its ends whereas overvoltage may occur along some points in between them. Thus, an alternative and feasible way for modelling the transmission line is proposed by the authors. Although the proposed method is not new, it is has not been usual. For showing the importance of the proposed method a real 230 kV/197 km transmission line are taken and simulated results do show how the occurrence of overvoltage is possible, not only under fundamental frequency but also for harmonics. All the presented results are a clear evidence of the need in reevaluating some conceptions of insulation coordination for power transmission lines.