COMPUTATION OF ELECTROMAGNETIC TRANSIENTS USING DUAL OR MULTIPLE TIMESTEPS

When computing transients with the EMTP (the Electro-Magnetic Transien ts Program) a single time step is selected for the trapezoidal integra tion all over die system. When this step is small because of the prese nce of a ''fast'' component, the simulation may be significantly slowe d down. This paper presents a procedure by which the computations at s elected fast buses can be performed with smaller time steps than at th e rest of the system. The linkage of the variables at two different ti me steps is achieved in a simple way at the line-bus interface by a sm all addition to any existing implementation of an electro-magnetic tra nsients program. Significant computational savings can be obtained wit hout any loss of accuracy.