1 DETERMINE CURRENT TRANSFORMER SUITABILITY USING EMTP MODELS

Current transformer (CT) and relay modeling are practical tools to evaluate protection equipment performance. This paper demonstrates the use of a set of software tools- Electromagnetic Transients Program (EMTP), The Output Processor (TOP), and Mathcad - to model transient events in the power system, as well as relay response to those events. The paper provides step-by-step instructions for using these tools to better understand and protect power systems. Specifically, in this paper we: 1. Model CTs using EMTP to visualize transient events. 2. Transfer EMTP output into Mathcad to examine CT accuracy, burden effects, saturation, and subsidence. 3. Model digital relays in Mathcad to show the effects of CT saturation on overcurrent, distance, and directional element operation, making relay response to transient events easier to understand