Computation of electromagnetic transients using dual or multiple time steps

When computing transients with the EMTP (electromagnetic transients program) a single time step is selected for the trapezoidal integration all over the system. When this step is small because of the presence of a fast component, the simulation may be significantly slowed down. The authors present a procedure by which the computations at selected fast buses can be performed with smaller time steps than at the rest of the system. The linkage of the variables at two different time steps is achieved in a simple way at the line-bus interface by a small addition to any existing implementation of an electromagnetic transients program. Significant computational savings can be obtained without any loss of accuracy