Considerations on power quality measurements and measurement instrumentation

The inherent differences in the accuracy of measuring/monitoring power quality (PQ) instrumentation has led the Brazilian Transmission Independent System Operator (ONS - Brazilian ISO) ONS to conduct a comprehensive field campaign and laboratory tests. These tests have allowed for evaluation of the accuracy and measurement methodology for a large number of commercially available instruments. This paper presents the laboratory test results for the performance of the different instruments. All of the instruments were simultaneously fed the same voltage signal. Lab tests were conducted which included most commom power quality indices such as: steady state voltage, frequency variation, unbalance voltage, voltage fluctuation and short duration voltage variation (sag).