Biweight Midcorrelation Based Transmission Line Pilot Protection Algorithm

This paper presents a novel pilot protection algorithm for alternating current (ac) transmission lines that relies on biweight midcorrelation (BWMC) coefficients between the terminals’ currents. The proposed solution was compared with recent and similar literature alternatives, and the results indicate that it is both effective in detecting faults of any type and that, as it is median-based, unlike the techniques used so far, the BWMC-based algorithm may be advantageous over existing methods as it presents higher robustness to not incorrectly trip on external faults, mainly under the critical conditions of CT saturation, noisy measurements, and sample misalignment, typically associated with outliers. The algorithm also proved effective against simultaneous multi-faults, weak infeed, power swing, multiple cases on different lines, and faults with time-varying transition resistance. The BWMC-based solution was finally experimentally tested in real-time with a hardware-in-the-loop system containing a CMC-256 set, an IEC 61850-based IED that embeds the algorithm’s logic, and current measurements recorded during actual faults on existing 500 kV lines from the Brazilian interconnected power system. All analyses indicate that this new algorithm can be a rapid, reliable, and robust solution.