The Rogowski coil based electronic current transformer has no saturation phenomenon

thus it can completely eliminate the misoperation of differential protection due to CT saturation.The transient characteristics of ECT and the impact of integration time constant on transient characteristics of Rogowski coil are described in this paper.Taking the fiber longitudinal differential line protection as an example

the performance of longitudinal differential protection using ECT is analyzed based on experimental data.It is shown that by using ECT

both the sensitivity and reliability of the relay protection are improved

and the operation property of conventional two-stage percentage restraint differential protection is meliorated.To meet the practical requirements

an implementing scheme of the interface between ECT and fiber longitudinal differential line protection is designed conforming to IEC 61850 standard.Moreover

a hardware scheme of data merging unit is proposed.