Método dos elementos finitos aplicado para cálculo de campos eletromagnéticos excitados por descargas parciais em hidrogerador

Abstract

This study aims to develop and numerically simulate a three-dimensional model of a hydrogenerator subjected to partial discharge (PD) and analyze the resulting induced voltage and field. To achieve this, an electromagnetic model was developed based on the finite element method, representing a twelve-degree angular sector of a hydrogenerator from the Campos Novos power plant. The model’s properties were carefully selected to accurately reflect the physical characteristics of the real machine. The definition of the magnetic core parameters of the stator was based on a study of losses and wear mechanisms in the material used in hydrogenerator stator cores, allowing for the selection of appropriate magnetic permeability for a linear simulation. To simulate PD in the numerical model, a small unitary current source was introduced to represent the discharge channel at two different positions on one of the stator windings, using a frequency of 40 MHz. For the calculation of the induced voltage, line integrals of the electric field were computed between the grounded floor of the enclosure and different points of the windings. The obtained results indicated mechanisms of electromagnetic wave propagation within the hydrogenerator environment, with the stator’s magnetic core acting as a wave guide for the induced field and the stator bars functioning as shielding. It was observed that the induced voltages were of higher intensity in the windings closest to the PDs, suggesting that this methodology can be used for the localization of partial discharges.