One-terminal fault location for VSC-HVDC transmission lines based on the feature of overlapped traveling wave

In order to guarantee the reliable reliable operation of voltage source converter HVDC (VSC-HVDC) system, we have proposed a one-terminal fault location algorithm for VSC-HVDC transmission lines based on travelling wave superposition. Because large capacitors are shunted on both terminals of the VSC-HVDC transmission lines, when a one-terminal ground fault occurs on the DC lines, the voltage travelling waves in the faulted component network of mode 1have two features: they have total reflection at two-terminal DC buses, and refraction mainly at fault points; the reflection leads to alternation of the voltage polarity, but the refraction does not. Therefore, if taking the time when the first travelling wave arrived at the measuring point as the originating time, a fault can be located as the strongest overlapped point between forward and backward travelling waves through calculation. Then the distance from this overlapped point to the opposite terminal is the fault distance. PSCAD simulation results show that the proposed method has error less than 0.06% in locating faults, and can tolerate transition resistance up to 300 Ω. It is concluded that this method is accurate in locating faults and helps to realize automatic fault location, so it can be adopted for VSC-HVDC transmission lines.