Equivalentes de redes elétricas e redução de tensão de restabelecimento transitória.

Abstract

This work presents a parameter estimation technique of Frequency Dependent Network Equivalents (FDNE) for application in Transient Recovery Voltage (TRV) studies. Contributions are presented to represent the network equivalent, assuming the attributes extraction of harmonic impedance components near the resonance points. A methodology is proposed for spectrum acquisition of the real external network. Routines are implemented to calculate the parameters that form a lumped model, providing good accuracy. The validation is performed in frequency and time domains, reducing electrical system modeling, ensuring reliability to assessments. Additionally, to minimize dielectrical stresses imposed by TRV, subsidies are offered to scale a device composed by Zinc Oxide (ZnO) varistors to limit TRV peak. Laboratory conditions are reproduced by digital tests. Low frequency cases require more energy from mitigating device, however, it is possible to characterize the number of discs needed to reduce TRV peak to acceptable levels specified by manufacturer standards. The results obtained in assessment presented good agreement, showing that the device can become permissive operations preliminarily qualified as unsafe. Financial support usually used to replace equipment by another with higher voltage class can be reduced.