Temporary overvoltage suppression in half-wavelength transmission lines during asymmetric faults

Abstract

This paper approaches the principal electric characteristics of half-wavelength transmission lines and possible voltage transients resulted from asymmetric faults. Although this non-conventional AC transmission technique presents some attractive advances for electric power transmission through long distances, when compared to the well-established HVDC systems, some important issues should be investigated on eventual overvoltage levels along half-wavelength transmission lines during temporary asymmetric operation conditions, e.g. phase-to-ground fault and single-phase reclosing. In this research, an iterative computational routine locates the overvoltage points by varying the asymmetric fault location from the sending to the receiving end of the transmission line. This procedure provides a full mapping of the most critical overvoltages as a function of the fault point through the line length. Since the most critical fault occurrences and overvoltage locations are known, an alternative method for overvoltage suppression is proposed by using line surge arresters directly at the phases in parallel with the tower insulators. This technique represents an original method to contain overvoltages at middle sections of half-wavelength transmission lines.