On the accuracy of the Phase-domain model for EMT analysis of transmission lines and cables

The Phase-domain (or Universal) line and cable model (ULM) is one of the most advanced in its class. This model is synthesized from frequency-domain transmission line relations in three stages involving rational fitting, state-space analysis and numeric integration. Each one of these stages implies an approximation and this paper presents an evaluation their impact on the accuracy of the final model. First, a version of ULM is produced in the MatLab platform. Then, the numeric-error increase at each stage is evaluated in the implemented version through the Numerical Laplace Transform technique (NLT). Next, the accuracy of the implemented model is tested under three different numeric integration rules: Trapezoidal, Backward Euler and Gear Second Order. Finally, the implemented model is compared with the one available in an industrial-grade EMTP.