Validação de metodologia para o cálculo de tensões induzidas por descargas atmosféricas indiretas na fiação de uma usina fotovoltaica

Abstract

The recent growth of large photovoltaic power plants in Brazil in areas with high rate of lightning has raised concerns about protection of its equipment. Although the effect of direct flashes can be mitigated by conventionally installed lightening captors, little can be done to prevent the lightening electromagnetic fields from illuminating the plant. The induced voltage generated by the indirect lightning, close to the photovoltaic power plant, can damage sensitive semiconductor devices such as photovoltaic cells, bypass diodes and the circuitry present in the installation, once that these effects cannot be fully avoided by lightning captor, reducing the power plant life cycle. In light of this information, this dissertation aims to validate a new approach in calculating the induced voltage in loops by an indirect lightening through a methodology initially proposed by S. Rusck for overhead distribution lines. Unlike the methodology traditionally found in literature for calculating the induced voltage, which only considers the magnetic field and uses concentrated parameters, the new approach proposed considers all fields effects originated by the current path due to the return stroke current and models the loops as transmission lines. The validation of this approach was made by comparing the results of the computational simulation with the results measured in scaled models, both cases for perfectly conducting soil. Measured and simulated curves were compared visually by plotting both results in the same graph to evaluate the convergence between the two curves and quantitatively, that was done by measuring the difference between the peaks, which is the most important value for the definition of the supportability of the equipment, and the Root-Mean-Square-Error, usually used for evaluate the difference between two curves.