Fundamental Investigations on the Aging of Insulating Materials under Harmonic Distorted Voltages

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The increasing incorporation of renewable energy sources into the electric power systems results in an increasing usage of power electronics. Due to their high switching frequencies, modern power electronics systems are space-saving, efficient and allow flexible operation in energy generation. An example is the solid state transformer, which is generally applied in medium voltage electric grids, transportation and offshore plants due to its compactness. However, the high switching frequencies of power electronics can induce harmonics, which possess frequencies higher than the grid frequency (50 Hz/60 Hz), resulting in a superimposed voltage and thus cause voltage distortion. Voltage distortion can affect the aging of insulation materials applied in electrical equipment, such as epoxy resin and silicone. Other than provoking additional dissipated heat due to increased dielectric loss, voltage distortion can also influence aging processes in terms of electrical and partial discharge aging. The aim of this project is to investigate the electrical and partial discharge aging processes of the insulation materials when stressed with a non-standardised distorted voltage. The influence of the distorted voltage on the voltage endurance behaviour are to be determined. The measurements are conducted on solid insulation materials such as epoxy resin and silicone, which are, amongst others, used in power electronics components and found in power electronics controlled equipment. The investigated voltage waveforms include typical grid voltage distortion as well as superimposed voltages with higher frequencies, which can occur in power converters. Based on the measured results, an advanced phenomenological aging model incorporating the additional stress caused by distorted voltages will be developed. The cooperation between University of Applied Sciences Zittau/Görlitz and TU Dresden allows the combination of the respective expertise regarding distorted voltages as well as electrical and partial discharge aging. The investigations contribute to a better understanding of aging processes in solid insulation materials. Specifically, the advanced aging model, which also takes the additional stress due to distorted voltages into account, will enable the improvement of state-of-the-art and future electrical equipment with to regard the reliability.