Contents I. Introduction
The polluting loads detection in power system has become a topical issue for power quality assurance and for the attribution of responsibility between customers and utilities for disturbances caused on power systems. As regard this, it is known that the traditional quantities used for the electrical energy pricing (active, reactive and apparent powers and energies, and related power factor) cannot give any useful information concerning the polluting sources, because they are well defined only for sinusoidal voltages and currents and they do not take into account the presence of harmonic distortion at the metering section. Furthermore, the current standards on power quality and harmonics do not define any measurement methods for the detection of harmonic sources. As regards the definitions and measurements of electrical quantities in nonsinusoidal situations, the only available standard is the IEEE Std. 1459-2000 [1], which provides a set of definitions of electric power, in order to quantify the flow of electrical energy in single-phase and three-phase circuits under sinusoidal, non-sinusoidal, balanced, and unbalanced conditions. However, the defined power components are not able to provide any information about the individuation of the harmonic sources. The only quantity that is meant to be used for this purpose is the harmonic active power, but it has been demonstrated that in some practical situations this approach cannot provide a correct information about the identification of the harmonic sources. In literature this matter is still debated and different approaches can be found, concerning the definition of proper indices and related measurement methods for the evaluation of harmonic distortion levels at the metering section and for the determination of loads and supply polluting contributions [2]–[7]. Most of them make use of the harmonic active powers and require to perform a spectral analysis of voltages and currents. On the other hand, in [8]–[9] the authors have shown that it could be interesting to pay attention to the nonactive components of the apparent power. In detail a novel single point approach was proposed in [10]–[13] for the detection of harmonic producing loads in power systems, both single-phase and three-phase. In detail, for the three-phase case, the approach was based on the simultaneous evaluation, at the same metering section, of different nonactive power quantities, which were derived from the effective apparent power resolution of the IEEE 1459 [11]–[12]. It was demonstrated that this approach was able to give some useful information on the location of the polluting sources and it was well suited also when both harmonic distortion and unbalance are present. Moreover, it was easy to be implemented because it is based only on the separation of the fundamental components from the harmonic content of voltage and current.
