Contents I. Introduction
In recent years, the monitoring of the voltage and current harmonic components in the power grid has become of greater interest due to the increasing connection of inverter-based renewable sources to the network [1] . However, the matter has been debated for a long time by research community [2] – [3] . The question has become more important also due to energy economic agreement issues. In fact, there are a lot of international rules that penalize the generation of reactive power by the loads but there is still not a common opinion on how this kind of penalization can be made with respect to harmonics [4] and how distortion can be taken into account for billing purposes. Actually, the standards for power quality [5] , [6] set the distortion levels based only on THD and single harmonics amplitudes. In [6] several power quantities definitions are introduced for quantifying flow of electrical energy. [6] also provides a set of power ratio indicators such as: line utilization, harmonic pollution and load unbalance factors. However, a standardization for harmonic pollution assessment has not yet made and this causes a difficult application of the penalty. The main challenge is the assessment of harmonic pollution sources or which is the contribution of each node connected to the grid to the total voltage distortion level.
