Load flow analysis using transformer models in alternative simulation tools

This paper describes procedures for modelling of two-winding off-load tap-changing transformers in two alternative simulation tools for load flow analysis — DYNAST and SimEPS. For both softwares, respective transformer models and other necessary simulation steps are introduced. Determination of all input parameters is presented along with the verification of results for single-phase transformer model in DYNAST when compared to measurement data. DYNAST is able to perform simulations by using physical diagrams, which are not standardly used for load flow analysis. However, it can also solve one-phase problems or even three-phase problems with real physical coupling. SimEPS models the load flow problem strictly by the system of equations and uses advanced computational algorithms to obtain highly accurate solutions. Load flow results from both softwares are compared and simulation errors evaluated for selected operational states of rather simple power systems.