Análise e detecção de falhas no enrolamento de transformadores de potência - modelagem, simulação e validação de métodos

Abstract

Power transformers are one of the most important and expensive components of an electrical system. Faults in these devices can directly compromise the efficiency and reliability of the circuit to which they belong. Analysis and detection of incident faults, especially winding faults, which account for more than 50% of occurrences, are crucial to ensuring reliable operation of transformers and the electrical sector. Therefore, this dissertation presents a literature review on these devices, their main components and faults, a review and validation of the main methods for detecting turns-to-turn and phase-to-ground faults. In addition, a review of the main simulation models reported in the literature is presented and a computational model in the ATPDraw environment is proposed that allows modeling of these devices under the incidence of winding faults, based on parameters determined through electrical tests or derived from their physical dimensions. The modeling was performed based on the results of open-circuit and short-circuit tests, and the fidelity of the model to reality was verified by comparing the simulated results with electrical tests performed on transformers in which winding faults could be introduced. For detection methods, frequency response testing, transformation ratio testing, and impulse voltage testing were used. These were performed on transformers with simulated faults of different intensities, and the ability of these tests to highlight the occurrence of faults was verified. The results indicate a high efficiency of the frequency response test in detecting faults of different intensities and transformers of different construction philosophies. However, for the transformation ratio and impulse voltage tests, there are conditions that limit their efficiency and restrict their widespread application. In addition, the proposed model showed a high degree of proximity to the real results but presented difficulties in representing equipment whose windings are divided into disks. This work therefore contributes to the state of the art in the analysis and early detection of faults in power transformer windings, provides a modeling method capable of simulating transformers with turns-to-turn and phase-to-ground faults, and validates certain methods for detecting these occurrences. Furthermore, the dissertation exposes the main impacts of winding disk division on the results of the tests considered and the limitations that this constructive philosophy entails.