Análise de falha em autotransformador associada à degradação da bucha de alta tensão - estudo de caso

Abstract

This work aims to carry out a technical analysis of the failure that occurred in a 500/138/13.8 kV power autotransformer, associated with the degradation of the sealing system of the high-voltage bushing, investigating the mechanisms that contributed to the dielectric deterioration of the equipment and to the development of the internal fault. For this purpose, the results obtained through field and factory inspections, electrical tests, physicochemical analyses of the insulating oil, internal inspections of the active part, and the operation of the transformer protection systems are evaluated. The study seeks to correlate the evidence identified during the diagnostic process — such as the presence of moisture, oxidation, partial discharges, and the formation of combustible gases — with the progressive degradation of the transformer insulation system.

In addition to the failure analysis, this work presents the stages of transformer disassembly, recovery, and rewinding, including the replacement of critical accessories and the execution of acceptance and commissioning tests performed after the repair process, aiming to verify the restoration of the unit’s electrical, mechanical, and dielectric conditions.

Finally, this work highlights the importance of periodic inspections, condition-based predictive maintenance, continuous monitoring, and the proper application of protection systems as fundamental strategies to increase operational reliability, reduce internal faults, and extend the service life of power transformers applied in highly critical electrical power systems.