A computer program has been written for the simulation of power system transients in real time. The program is based on EMTP models and solution techniques optimized for maximum performance in superscalar computer architectures. Timings ranging from 38 to 107 ps have been obtained for systems from 18 to 30 nodes using an JBM RISC System/6000 Model 560 workstation. These timings are considered adequate for real-time testing of protective relaying equipment. The program is compatible with existing E M " data cases.

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Due to synchronization requirements related to the interfacing with external systems, digital real time simulators of electromagnetic transients for equipment testing employ a constant integration time step width for solving the network equations. Therefore, the network solution is only calculated at discrete and equidistantly spaced time instants while in reality the time domain is continuous. Changes in network structure that occur between the discrete solution points are generally not simulated exactly. This can lead to switching control mistakes and numerical problems. In this paper the novel Clock Synchronized Structure Changing concept, which allows the accurate and efficient simulation of structural changes at arbitrary time instants, is presented.

Multirate simulation of electric networks exhibiting a wide variety of time constants decreases the simulation runtimes by exploiting the property of circuit latency. The fundamental idea is to use different integration steps for different network subsystems, according to the requirements of accuracy of each subsystem. Programs that exploit circuit latency are usually based on relaxation methods that require iterations among the different subsystems of the original networks. These methods lack the numerical robustness of direct implicit integration methods used in circuit simulators and are not adequate for real-time simulation due to their non-uniform solution times. This paper proposes circuit latency exploitation without iterations making use of the concept of interlinked Multi-Area Thevenin Equivalents (MATE). Results are presented showing the efficiency and accuracy of the method.