EXPERIMENTAL EVALUATION OF EMTP-BASED CURRENT TRANSFORMER MODELS FOR PROTECTIVE RELAY TRANSIENT STUDY

This paper describes an EPRI study of Current Transformer (CT) digital models intended for protective relay transient performance analysis. Experimental evaluation of CT models implemented using Electro Magneti c Transient Program (EMTP) was carried out. Two relaying CTs with 600/ 5 and 2000/5 ratios were used in the study. Experiments in a high powe r laboratory were performed to obtain transient responses. Simulation of the CT response to the same transient events was set up using three different CT models. They were implemented based on the saturable tra nsformer and nonlinear reactor models available in an EMTP. Comparison of laboratory and simulation results indicates that CT models develop ed based on the EMTP program give satisfactory results for most of the cases. It has also been discovered that in some instances EMTP models need further improvements.