Fault Tripping Criteria in Stability Control Device Adapting to Half-Wavelength AC Transmission Line

Because of the long distance and huge distributed capacity of half-wavelength AC transmission lines (HWACT), the fault characteristics of HWACT lines differ a lot from those of conventional lines. In this paper, the unique fault characteristics at the measuring points are simulated and the adaptation of conventional fault tripping criteria in HWACT lines is analyzed. It is pointed out that the stability control devices may operate incorrectly when the fault occurs far from the measuring point of the HWACT line. The fault location is determined by the starting time difference of the devices at both sides of the line. With the fault location and distributed element model of HWACT line, the voltage and current of the fault point are calculated and the new fault tripping criteria based on the electrical quantities of both the fault point and the measuring points are proposed. The simulation results show that the new criteria can distinguish the single-phase fault from phase-to-phase fault correctly and reliably.