Pearson correlation coefficient of current derivatives based pilot protection scheme for long-distance LCC-HVDC transmission lines

This paper proposes a pilot protection scheme for long-distance LCC-HVDC transmission lines based on Pearson correlation coefficient of current derivatives. According to the impedance frequency characteristics of converter and DC filter, and the superposition principle, the correlation characteristics between line current derivative (LCD) and DC filter current derivative (DFCD) are analysed for internal and external faults. For internal fault, there is completely negative correlation between line current derivative and corresponding DC filter current derivative at both rectifier side and inverter side; for external fault, the correlation of current derivatives (CDs) at the faulty side is positive, yet completely contrary at the other side. The Pearson correlation coefficient (PCC) is utilized to detect the correlation characteristics of current derivatives. And based on these characteristics, a novel protection scheme for long-distance HVDC transmission lines can be constructed to detect internal and external faults. Comprehensive simulation results show that the proposed protection scheme can quickly identify internal and external faults with high reliability. Furthermore, it is insensitive to fault resistance, fault location and measurement noise, and does not require data synchronization.