A new protection principle for HVDC transmission lines based on fault component of voltage and current

The paper presents a new protection principle for double circuit transmission lines of bipolar HVDC transmission system. By comparing the magnitudes of fault component of voltages on the bipolar lines, the faulty line can be identified. By comparing the polarities of fault component of currents at the ends of the faulty line, the internal faults and external faults can be differentiated. The principle can be applied for bipolar neutral grounding at both ends and monopolar metallic return mode operation. Different conditions are considered to research the operating characteristic of the proposed protection criterions, including short circuit faults on AC-side bus, commutation failure, lightning stroke and short circuit faults on dc transmission lines with different positions and transition resistances. Simulations results show the selectivity, speed, sensitivity and reliability of the protection principle, and the sampling frequency requirement of measuring instruments in the protection scheme can be 10~ 100 kHz.