Evaluation of fault protection methods using ATP and MathCAD

This paper discusses combining the Alternative Transients Program (ATP) and MathCAD to teach protective relaying and to develop relay algorithms. A power system model is created in ATP with appropriate current and voltage measurements. The simulation output is converted to a COMTRADE format and imported into a detailed relay model implemented in MathCAD. The MathCAD model performs digital filtering calculations, symmetrical components calculations and models relay algorithms based on relay manufacturers published information. Focus here is on differential and ground fault protection for the common two bus, parallel line case. Emphasis is placed on fault detection and localization methods for ungrounded or high impedance grounded systems.