A novel summation impedance protection adaptive to high‐resistance earth fault detection

Abstract

While the high‐resistance earth fault frequently occurs on extra high voltage (EHV) transmission lines, existing protection schemes show great limitation for coping with this kind of fault scenario when the fault resistance is very high. In this paper, a novel protection methodology combining the measured impedance of the two ends is introduced, and a so‐called summation impedance protection, making use of this critical information, is thus put forward and assessed. Emphasis is placed on the principle of the summation impedance protection and its adaptive thresholds. A simulation model based on EMTDC/PSCAD, by which the performance of the summation impedance protection is evaluated, is then established. As confirmed by quantitative theoretical and experimental studies, the results indicate that the proposed protection scheme works well even when the fault resistance is extremely high under the internal fault condition, and it keeps itself from maloperation as an effect of its adaptive thresholds wherever an external fault occurs. These results highlight the necessity to work in conjunction with the existing main protections of transmission lines, by which means an enhanced ability to cope with the high‐resistance single‐phase earth fault can be achieved. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.