Determinação da tipologia de curvas de carga em frequências harmônicas para consumidores residenciais de baixa tensão.

Abstract

The correct characterization of the load curves of consumers connected to electric grid, especially in the low voltage segment, is of fundamental importance for the strategic planning of electric energy distributors. Additionally, this characterization, represented in a practical way through the typologies of load curves, is used by ANEEL aiming at the establishment of regulatory methods for the formation of prices to consumers, contemplating aspects such as quality of supply, as well as the determination of loss coefficients referring to transformers, low voltage circuits and connection branches of consumer units. In this context, the current load characterization model for electric energy distribution systems considers only active and reactive powers at the fundamental frequency, and this process is carried out through measurement campaigns, whose guidelines are established by ANEEL through the Module 2 of PRODIST – Distribution System Expansion Planning. However, the consideration of load curves contemplating only the fundamental frequency of the system does not reflect the real profile of the electrical loads that currently constitute the distribution systems, since almost all these loads have non-linear characteristics in relation to the imposed voltage, resulting in the injection of harmonic currents in the electrical grids. Given this context, the objective of this work is to identify the harmonic components present in residential loads and define the typical load curve, in terms of amplitude and phase angle, of the different harmonic components of current injected by residential consumer units. In order to achieve this objective, a measurement campaign was carried out that contemplated the parameters referring to the harmonic current in a large electric energy distribution company. Thus, with the measurement records (mass memories) associated with almost five hundred residential consumer units, each monitored through digital meters, for a minimum period of seven consecutive days, the available data was processed and, subsequently, the application of the cluster grouping technique, called k-means, aiming at the characterization of typical curves of residential harmonic loads. The results obtained allowed the temporal characterization of the direction and intensity of the harmonic flow in the connection branches of low voltage residential consumers properly stratified in different consumption classes, contributing, consequently, to a new model of load characterization, where a trend of greater injection of harmonic components into the distribution network by consumers with greater purchasing power. Finally, based on this characterization, the technical losses of a given medium voltage distribution feeder were calculated considering two different scenarios: (i) consideration only of load typologies at fundamental frequency and (ii) consideration of load typologies at fundamental and harmonic frequencies. The obtained results evidenced the importance of the typology of harmonic loads in the scope of the electric energy distribution systems.