Avaliação de sobre aquecimento anômalos em cabos elétricos de parque eólicos.

Abstract

This work evaluates power quality and energy efficiency in wind farms. The main focus is the analysis of the skin effect caused by harmonics in the cables of real wind farm installation. Data presented in the study of power quality performed to obtain access to the electric system operator, was used for the development of this research. The software HarmZs, commonly used in power quality studies, was used to obtain the harmonic distortion values for currents measured at wind farm site. The wind farm presented problems in the power quality delivered at the point of common connection to the national electrical power system. The additional losses calculations for the wind farm internal system presented an increase of up to 8% caused by the harmonic currents in the installation of the wind farm. With the aid of the software COMSOL Multiphysics®, the current density distributions from the harmonic currents in the cables were evaluated. The cables used for this study are implemented in the connection between wind turbine and elevator transformer. These cables present greater harmonic current distortions. It has been found that adjacent cables interfere with current density distribution and that the current density increase at cable end can reach 68% when compared to the case where there is no interference from adjacent cables. Finally, the thermal analysis in the cables indicated an elevated temperature, 136oC, for the conductors of phase B. The increase of temperature observed can be mainly attributed to the losses due to the fundamental component current and the process of thermal conduction between phases.