T. Sels, J. Lopez-Roldan, J. Declercq, D. Van Dommelen, and R. Belmans
Electrical insulation, fast transients, Tesla transformer, reliability, power quality
A few cases of recent failures in transformers have been seen as the precursors of a measuring campaign to investigate the possible causes and failure mechanisms. The results of the measurements pointed towards the existence of high-frequency pulses superimposed on the 50 Hz fundamental voltage. The effect of the pulses was a breakdown of the internal winding insulation of the transformer. Further research assigned those pulses to switching operations in the grid and resonance phenomena in the transformer windings. Therefore, a test circuit is developed in the laboratory to study the failure mechanism of the electrical insulation exposed to this specific voltage waveform in a controlled environment. The main element of the circuit is an extended Tesla transformer. The final test circuit is used in the laboratory to perform aging tests on different electrical insulation materials. A high-frequency pulse is generated and superimposed on the 50 Hz rated voltage of the insulation under study. The goal is to cover the gap between the research of aging mechanisms at frequencies from DC to several kHz using a perfect sine wave, and the research on the breakdown mechanism due to impulse or steep front voltages.
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