A novel pilot protection method for UHVDC transmission lines based on U-I characteristics

Abstract

As one of the principal protections of UHVDC transmission lines, pilot protection requires strict synchronization and small data flow by exchanging the current on both terminals under the limitation of DC protection action rapidity. To solve this problem, this paper finds that the DC voltage and current on both terminals of the line have different plane distribution characteristics when faults occur internally and externally in the system area, and then advances a novel pilot protection method for UHVDC transmission lines based on U-I characteristics. By setting up the U-I plane with DC voltage and current as variables, analyzing the dynamic trajectory of the real-time captured U-I plane, constructing protection criteria based on the U-I plane on the rectifier side and inverter side separately, and finally converting the judgment results into state information. Both terminals of the line identify the fault location by exchanging the longitudinal comparison of state information. This protection project only utilizes the instant tracks of voltage and current in the rectifier side and inverter side at the time of fault to judge. The principle is simple and can quickly locate faults. The state messages of the two terminals are not modified by the data asynchrony on both terminals. This protection method is convenient for setting, has high sensitivity, and can quickly identify interior and exterior faults. The results are testified by theoretical analysis and simulation verification.