Optimum time step size and maximum simulation time in EMTP-based programs

This paper presents a general algorithm to calculate an optimal time step size and a maximum simulation time for EMTP-based programs. This is of particular importance for new users of EMTP-based programs, since the user is responsible for setting up these parameters before running a simulation case. The selection of the time step size affects the precision of the simulation. The time step size depends on the maximum frequency expected in the phenomena, which is normally unknown, a priori. A robust algorithm is presented here based on all the input data given for the circuit under simulation. The proposed calculation process is based on single-or multi-phase uncoupled or coupled circuits, with lumped or distributed parameters. Simulations are given demonstrating the effectiveness of the proposed rules. A future challenge will be the creation of a methodology capable of adapting the time step size dynamically.