The current transformer model with ATP-EMTP for transient response characteristic and its effect on differential relays performnce

This paper presents the analysis of current transformer transients. The model is constructed on EMTP (Electromagnetic Transients Program). In the current transformer model, the secondary winding is connected in parallel with a magnetizing branch with non-linear characterestics of the inductor. Type-96 pseudo non-linear hysteristic inductor with saturation and hysteresis charecteristics is used incorporated with the sub-programs “SATURA” and “HYSDAT”. These programs are employed in data of saturation and for input data of the inductor. The analysis is taken into account effect of, burdens, accuracy classes on current transformer performances. Data protection system of 20 MVA and 75 MVA power transformers are used in the study. The results can be used for the programma model Freja 300 relay testing machine system for operating performances of the relay. In addition, appropriate current transformer and protection relays can be selected based on the results.