The first chapter of this book is dedicated to the problem of measuring basic electric quantities in electric utilities (voltage, current, power, frequency), both from the aspect of accuracy of this type of measurements and the possibilities of simple and practical realization. The conventional algorithms used to this purpose (calculating the active power and the RMS value of the voltage and current signals that are the object of processing) are based on the use of integration or summation process on limit time interval. A characteristic of this approach is that it offers the correct result if the input signal is periodical in time. However, in real systems, voltage and current signals are not necessarily of a periodical quanity, due to the presence of nonharmonic components or/and possible stochastic variation. It is for this reason that, very often, the result of processing is not an instantaneous value of processing signal — it is rather a processed (observed) value in some time interval, both with conventional and certain new algorithms for processing [1–19].