Novel pilot protection principle for high-voltage direct current transmission lines based on fault component current characteristics

For high-voltage direct current (HVDC) transmission systems, the transient fault current characteristics are that: if the fault point is over the line, the fault component current measured at both converter stations would be increased and they have the same changing direction. If the fault point is beyond the line, the fault component current measured at one converter station is increasing and the fault component current measured at the other converter station is decreasing, so they have the opposite changing direction. According to this characteristic, a novel pilot protection principle for HVDC transmission line based on fault component current is proposed here. The principle proposed has no limitation to the sampling frequency. A fault, whether it occurs in the line or beyond the line, can be effectively identified only using the fault component current at both converter stations. At the same time, the setting criterion of the fault component current is also given. The simulation results show that the new method can identify the faults reliably and rapidly. The study is promising to have significant theoretical and practical value.