Improved Zone 1 Top-line Tilting Scheme for Polygonal Distance Protection in the Outgoing Line of Type-4 Wind Parks

The impedance element in distance protection equipment in the outgoing line of a wind park (WP) may be heavily affected by the fault response of the WP. During resistive grid faults, relay over-reach (or under-reach) may manifest, depending on the fault current regulating requirements in the specific grid code deployed in WP and the fault conditions. Aiming at potential solution, i.e. the existing zone 1 (fast tripping zone, non-delayed) top-line tilting (Z-1-TLT) function in modern numerical relays, this paper first assesses its adaptability under the WP integrated background. Combining the principle of Z-1-TLT itself and fault modeling to the WP, an improved Z-1-TLT scheme is developed, which can actively compensate for the possible relay overreach or under-reach during resistive faults, utilizing relay side fault quantities only. Aiming at the needless action of the new Z-1-TLT scheme against certain faults, malfunction risk area detection and dead zone detection are introduced as auxiliary criteria to optimize protective efficiency. Simulation results prove the improved Z-1-TLT scheme can effectively improve reliability of distance protection deployed in the WP outgoing line.