Análise da degradação de isolamentos poliméricos.

Abstract

Electrical insulators perform an essential role in the electrical energy transportation systems, directly influencing their efficiency and reliability. Historically, the traditional electrical insulators in use have been the ceramic models, composed of glass or porcelain. Nevertheless, in the last few decades, a new class of insulating materials, made of organic compounds, has been widely applied: the polymeric insulators. Because they are relatively novel, the behavior of polymeric insulators is not fully known, and these equipments require more efficient monitoring techniques, and deeper studies of their failure mechanisms. Aiming a wider comprehension of the factors responsible for the degradation of polymeric insulators, accelerated aging tests were performed in several models of insulators, spacers and other accessories. These tests allowed the determination of the contribution of factors such as ultraviolet radiation, water deposition, high temperatures and electrical voltage in the degradation of the equipments. The artificial aging of the samples, in laboratory, allows the analysis of these factors exclusively, which can rarely be obtained in field conditions. Five diagnostic techniques were used to evaluate the integrity of the samples: leakage current measurement, partial discharges, withstand voltage and flashover voltage, both in dry conditions and under salt fog. Leakage current and partial discharge measurements evidence a greater degradation of the samples exposed to electrical voltage and salt fog, while the flashover voltage tests indicate an inferior supportability of the samples aged through ultraviolet radiation exposure.