A Digital Simulator for Determining the Performance Limits of Computer Relays

Unlike most other digital simulators that generate test waveforms for specific system configurations, playback previously recorded fault waveforms, or randomly generated artificial waveforms, the digital simulator presented in this paper generates the worst-case waveforms for specified bounds on noise components present in the relay input signals. As a result, the performance limits of a computer relay can be determined, for specified bounds on its noise components, by performing a single test only. The parameters that define the worst-case waveforms are obtained by utilizing a modified univariate search algorithm. The PC-based simulator was implemented using a general-purpose multifunction card and a graphical programming package called Visual Designer. It did not require any text-based programming for tasks such as interfacing, digital-to-analog conversion, and outputting the discrete analog values of the generated waveform under hardware control. For demonstrating the operation of the digital simulator, a computer relay was also developed in the laboratory and its performance limits were determined.