Natural frequency based protection and fault location for VSC-HVDC transmission lines

With excellent priorities, Voltage Source Converter based HVDC (VSC-HVDC) will be the promising offset of HVDC transmission technology. This paper presents a protection and fault location method for VSC-HVDC transmission lines using one terminal current data. The proposed method is based on the natural frequency from the reflection process of traveling wave on a distributed parameters transmission line. As the presence of the large shunt capacitor on both terminals of the VSC-HVDC lines, the high frequency traveling wave is close to total reflection on the terminals. Therefore, the value of natural frequency of VSC-HVDC transmission lines is only related to fault distance and travelling wave speed, and the magnitude of natural frequency signal is related to the fault resistance. According to these characteristic, a single-end protection and fault location method is proposed. Compared with traveling wave method, the proposed natural frequency method is more simple and reliable. It does not need to detect accurate wave-front arriving instant with high sampling frequency. The proposed method is verified using the frequency-dependent line model in EMTDC. The simulations have shown that this method is valid and is capable of locating the faults occurring on VSC-HVDC transmission lines quickly and accurately.