Análise dos impactos das distorções harmônicas de tensão sobre a ocorrência de descargas parciais utilizando um modelo de elementos finitos

Abstract

The monitoring of partial discharges (PDs) is one of the main techniques applied worldwide to assess the insulation condition of electrical equipment powered by medium and high voltage. The occurrence of PDs is normally related to the appearance of defects in the insulation system that, over time, can compromise the integrity of the dielectric material used, increasing the probability of complete failure. Laboratory tests for measuring and evaluating PDs are generally performed with the application of purely sinusoidal alternating voltages. However, due to the adversities of the electrical grid, it is very common for electrical equipment to be operated with voltages distorted by harmonic components at some point. In this context, this work aims to analyze the impacts of harmonic voltage distortions on the occurrence of PDs. For this, a dynamic model was implemented to simulate PDs based on the application of the finite element method (FEM). With this model, several simulations were performed applying distorted voltages composed of different harmonic frequencies, various levels of distortion, different phase angles, among other combinations. The results extracted from the simulations revealed that the harmonic distortions can cause variations in the number of PDs generated, as well as in the mean values of their charges. Deformations in the Phase-Resolved Partial Discharge (PRPD) patterns were also observed. Furthermore, the temporal evolution of the PDs was highly dependent on the characteristics of each analyzed waveform, such as inflection points and peak values. In general, for higher harmonic distortion levels, the effects on PD activities were more significant. In practice, some of these effects may contribute to the degradation of the dielectric material and impair the interpretation of PRPD patterns, making it difficult to diagnose the condition of the insulation system.