On the Measurement of Power-Quality Indexes for Harmonic Distortion in the Presence of Capacitors

Different techniques have been recently proposed in the literature for the identification of the sources of harmonic distortion in electric-distribution systems. Each of them has its own advantages and limitations as far as reliability, accuracy, and practical usability are concerned. In this paper, these techniques are grouped into three main fundamental criteria in order to investigate their performance in the presence of capacitors. A case study is analyzed by means of both experimental tests and computer simulations. The results put in evidence some major problems that may concern the information provided by the considered methodologies, in virtue of the interaction of the capacitors with the other network components.

I. Introduction

In a liberalized electric market, where the quality of the product provided by a utility can be a critical competitive item and can represent a clause of the contracts for supplying energy to the customers, measurements aimed at both, evaluating the so-called power quality and attributing the responsibility for its degradation, are assuming more and more importance.