A Novel Fault Monitoring and Location System for HVDC Electrode Line

The fault of electrode line can pose serious threat to the safe and stable operation of the High Voltage Direct Current (HVDC) system, but it is quite difficult to detect the line fault by normal ways because the grounding electrode line is usually at ground potential. This paper presents a novel fault monitoring and location system for HVDC electrode line, which is based on the TDR technique and specially designed according to the characteristics of electrode line. The system injects differential mode voltage pulse to monitor the electrode line, and reduces the cancellation of differential mode signal through series reactance. Theoretically, this system is immune to the interference signal from the HVDC system, and can greatly improve the Signal-to-Noise Ratio (SNR) of the reflected pulse. In addition, the system uses a waveform comparison algorithm to solve the problem of line parameter uniform and slowly changing, which could make much trouble to the normal TDR methods. For this fault monitoring and location system, the output pulse amplitude is designed as up to 500 V, the pulse width range is about 1-5 $\mu$s, and the pulse sampling rate is as high as 10 MHz. Simulation results and field applications show that this system can achieve excellent fault monitoring and location result for the HVDC electrode line, with the fault location accuracy better than 300m.