mproved 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.