Algorithm for single phase-to-ground fault digital distance relay

The value of the potential that appears at the fault location during a ground fault at a high-voltage overhead line depends on many different factors and cannot be considered as an a priori known quantity. Owing to this, the influence of this quantity on the current and voltage measured at one of the line terminals is also unknown so the fault distance cannot be exactly calculated, and as a final consequence, the relay may operate undesirably. It could happen especially in the case of the relatively short lines such as those in sub-transmission systems. The development of the proposed algorithm is based on the complete transmission line model under ground-fault conditions that include ground-fault current component coming from the remote end. The proposed algorithm has been tested using the simulated current data. Sample test results have also been presented in this study.