Repetitive transient aging, the influence of repetition frequency

Power electronic devices are required in the modern grid in order to make a “bridge” between the DC and AC waveforms. These power inverters perform fast switching operations thanks to IGBTs and create fast repeating transients that are injected to the next HV component in line, e.g. a transformer. The transients are characterized by three main parameters: high repetition rates, fast slew rates and high magnitudes. This contribution presents the findings related to the repetition frequency. It was observed that the dielectric quality and lifetime decrease considerably when the frequency is changed from 1 kHz to 10 kHz. For this purpose, an experimental waveform is presented in this paper together with a broad explanation of the various phenomena that occur in the paper impregnated insulation.