Distortion sources identification in power systems with capacitor banks

The identification of distortion sources in a power system is a topic unsolved. The problem has a difficult solution because there are elements in the system that do not produce harmonic but amplifies the existing in the electrical network. The most common of those elements is the capacitor, very used to compensate power factor at fundamental frequency. The capacitor behaviour makes that the indices proposed up now to identify distortion sources fail in the presence of this element. In this paper, a new index is presented: the load characterization index. Besides using an extended equivalent circuit to represent the load, this index calculates the distortion introduced by the load, evaluating, besides the current distortion at its input, the voltage distortion at its terminals. The introduction of voltage assessing makes the index suitable to identify the linear and nonlinear loads in the power system even in the presence of capacitors and only from the voltage and current measured at the point of common coupling.

I. Introduction

In a liberalized electricity market, the electric power quality, EPQ, in the grid can be a critical competitive parameter and may represent a key to supply contracts. Both, measures and assessing consumers' contribution to the EPQ are becoming increasingly important [1]–[4]. Harmonic distortion is one of the main aspects of power quality and it is the fastest growing in importance in recent years because of the proliferation of nonlinear and time-varying loads in power systems, which absorb non-sinusoidal currents.