Avaliação do Desempenho de EPDM e EPS em Bucha de espaçamento para Transformadores de Corrente sob Testes de Descarga Parcial

Abstract

The reliability of current transformers is directly proportional to the quality of their electrical insulation, usually consisting of oils, resins, bushings, or polymeric compounds. One of the main failures of this insulation system is the occurrence of partial discharges, which can happen in various locations: inside the winding, due to the formation of air bubbles, impurities, or problems in the impregnation process; in the insulating bushings, due to surface contamination, roughness, or wear of the polymeric material; or in adjacent cables and connections, in locations with a high electric field gradient. The main objective was to analyze the performance of Ethylene-Propylene-Diene Monomer (EPDM) and Expanded Polystyrene (EPS) terpolymer materials used in the spacing bushings that accommodate the cables in the current transformer window, verifying their influence on the occurrence of partial discharges and the reliability of the insulation system. The methodology adopted employed a qualitative and quantitative approach, based on a literature review and a technical-experimental case study. Tests followed the guidelines of IEC 60270 and IEC 60034-27-1 standards, which establish the principles for apparent load measurement and procedures for off-line testing in electrical systems. The results demonstrated that replacing EPDM with EPS does not compromise the dielectric integrity of the equipment, as both showed satisfactory performance under nominal voltage (13.8 kV). However, under overvoltage conditions, EPS exhibited superior behavior, with no relevant evidence of partial discharges, while EPDM registered significant partial activity.