Compensation of the current transformer saturation effects for transmission line fault location with impedance-differential relay

Abstract In this paper, the impedance-differential protection dedicated to transmission lines is analysed. The considerations are focused on the extra function of such protection, namely the ability to accurately determine the fault location for an inspection-repair purpose. Measurements of current and voltage at both line ends allow to formulate a differential impedance which constitutes an efficient criterion for fault locating. However, the considered fault location may face a problem when faults with current transformers (CTs) saturation take place. Therefore, in this paper, the proposal aiming at improving fault location accuracy by compensating the CTs saturation effect is introduced. For this purpose, the compensated current was determined by using voltages from both line ends and current from not saturated side and then used in the proposed algorithm instead of the saturated current. The introduced algorithm enables for accurate fault location, even under deep CTs saturation condition. The developed solution has been thoroughly tested with the signals generated with the use of ATP-EMTP program.