Confidence levels in measuring the parameters of PQ. A case study

Evaluation of PQ parameters is made by means of the results of measurements. Because the evaluation of PQ parameters must be reasonable, the results of measurements must have a adequate confidence level. In this sense, have been established a number of requirements that are specified, for each PQ parameter, in IEC 50160:2010, IEC 61000-4-30:2008 and other related standards. One of the essential requirements, to measuring PQ parameters, is to ensure the measurement uncertainty specified in the standards. Since measurements are always accompanied by errors is very important for us to know the physical phenomenon, measurand and measuring conditions, for to act in minimizing the influence of errors. The accuracy and precision of measurement results in PQ, as well and their levels of confidence are various and depend on the determinations purpose. From this perspective, in IEC 61000-4-30:2008 are defined the classes of measurement methods (Class A, Class S and Class B) and the levels of uncertainty for each parameter PQ, [1].