The transient overreach phenomenon reduces the sensitivity of zone one protection of distance relaying. By analyzing the transient response characteristics of CVT and current transformer

this paper points out that the disaccord between CVT and current transformer of the non-period components transfer characteristics is the main reason of transient overreach. Hence this paper presents a novel method based on the differential equation algorithm. The algorithm superposes a synthetically attenuation non-period components to voltage in the secondary side of CVT that makes the non-period components of voltage and current in the secondary side nearly identical. So the calculation accuracy of fault distance is enhanced and the transient overreach phenomenon is ameliorated. The method has filtration capability because the least square fitting algorithm is used. The EMTP and fault record data simulation results show the correctness and feasibility of the proposed algorithm.