Unbalance compensated distance relay for active distribution networks

Abstract

Integration of Distributed Energy Resources (DER) into the Active Distribution Networks (ADN) causes issues in conventional overcurrent protection. Additionally, another conventional protection, such as the distance function, has been used, but ADN characteristics require new well-fitted approaches. This paper proposes a strategy to improve conventional distance relays when applied in unbalanced distribution lines. The strategy is based on the relay’s current and voltage measurements and the line series impedance matrix. Different overhead line cases are studied considering several pole geometrical arrangements and fault types. Based on the results, the new set of equations for distance-based protection can achieve a more accurate fault impedance estimation, with a maximum error of 0.1% in the analysed situations and despite the fault conditions. The high proposal performance and the straightforward application make this proposal suitable for the nowadays ADN protection.