An improved three-phase digital recorder system for calibrating power instrumentation

The paper describes an improved digital recorder system which is being used to provide reference values of voltage, current, active, reactive and apparent powers and harmonic quantities for three-phase sinusoidal and nonsinusoidal calibrations. The system has been designed to be used in the laboratory at the National Research Council of Canada (NRC) or transported on-site for tests in electrical utility facilities. Test results have shown that for sinusoidal waveforms, the accuracy of the voltage and current measurements of the digital recorder is better than 25 μV/V or μA/A of full scale and better than 50 μW/W of full scale for active and apparent power measurements. The accuracy of the system for measurements under the seven distorted waveforms conditions most commonly used at NRC is better than 50 μV/V or μA/A of full scale for voltage and current measurements and better than 100 μW/W or μVA/VA of full scale for active and apparent power measurements