Elaboration D’une Plateforme D’essai Dédiée Au Diagnostic Des Défaillances Dans Les Enroulements Des Transformateurs De Puissance

Résumé: Based on the fact that the electrical power transformer is one of the most important elements of the electrical network. Truly is a critical equipment that ensures the transmission of electrical energy with minimal losses in energy. Faults in the electrical power transformer system are anything that causes an abnormal change in current or voltage values. The most common cause of this is a breakdown in the insulation on the conductors due to electrical or mechanical pressures, due to the aging of the transformer, or due to external factors such as electromagnetic forces. Among the most critical aspects of a transformer that need to be monitored is the mechanical condition of the windings. The frequency response analysis (FRA) test is a reliable test to evaluate the mechanical integrity of the power transformer winding, and to detect other types failures that infect the core. Frequency Response Analysis (FRA) is a non-invasive, non-destructive and crucial diagnostic tool for assessing mechanical and electrical issues, allowing for proactive maintenance and preventing unexpected failures. A sinusoidal signal is injected into the winding input, so that the same signal is measured at the same time at the winding output, or in other words, the transfer function response is measured. In the healthy condition of the power transformer winding, it maintains the same signal. However, in the event of losses in the winding as a result of aging or electromagnetic forces, the exit signal is different from the reference signal. Electrical and mechanical faults in the winding of an electrical transformer are treated separately, and on the other hand, by considering that they occur together at the same time. Initially, a state-space model is developed with dedicated consideration a turn short-circuits faults in disks. The first step concerns the redefinition of the resistance, inductance and capacitance matrices to introduce the coefficients relating to defects. Simulating the frequency response by considering a short circuit fault at different rates and in different disks, to determine the extent of the effect of the short circuit on the behavior of the power transformer. This modeling makes it possible to propose new models adapted to the needs of power transformer diagnosis. Then, this thesis studies several winding deformations, which include axial displacement, radial displacement, and axial displacement with SC consideration. Conducting an investigation into frequency response analysis can be a powerful tool to study the impact of such faults on the behavior of a power transformer. Finally, In the final chapter of this thesis, a test platform was presented that provides the service of building an equivalent model of a power transformer. Also, one of the features of this platform is that it is a powerful tool that helps in conducting routine tests and safety tests to detect mechanical faults of the power transformer windings. In addition, a program was presented that automatically connects the LCR meter to the computer for the purpose of providing the necessary data obtained through tests, whether in design tests or startup tests

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