Proposing a New Approach to Generate the Differential Trajectory of the Differential Relays Using COMTRADE Files

Abstract

The differential relay is subject to transient events such as inrush current, which may affect its correct operation. Therefore, evaluating the reliable and accurate operation of differential relays is important, which is only possible by mapping the relay’s differential trajectory on its setting curve. However, except for the SIGRA software, creating a differential trajectory only for Siemens relays, there is a gap in developing a method to extract this trajectory for other commercial differential relays. Hence, in this paper, a new method for generating the differential trajectory of the differential relay from their six input currents and mapping it on the relay setting curve is presented. The proposed method uses the differential relay COMTRADE files to access the relay input currents during an incident. The currents recorded in the COMTRADE files belong to the secondary sides of the current transformers (CTs). Accordingly, the impacts of the current transformers’ connections and the protected transformer’s connection type should be considered in the proposed study. The ability of the proposed method to generate the differential trajectory for different incidents that occurred on the power transformers is evaluated using simulation studies and also according to the experimental tests. The results illustrate the efficiency of the proposed method in generating the differential trajectory from the COMTRADE files. In addition, comparing the results of the proposed method with the results created in SIGRA software shows the higher accuracy of the proposed method in producing the differential trajectory of the differential relay.