Pulsed Techniques for Accelerated Electrical Aging of Solid Insulation Materials and Components of HV Power Supplies

This paper briefly describes wide-band HV generators for insulation testing providing range of 0-200 kV, quasi-rectangular waveshapes, with pulsed repetition rates to ≈200 Hz. It is concluded that such generators, even their commercial versions, are robust, compact, and flexible enough for wide-ranging insulation tests in industrial environment. Examples of specimens’ construction, test regimens and life tests results for two selected silicone potting materials into hundreds of millions of pulses at 50 kV-200 kV are given. This was done on multiple samples with geometries having a field nonuniformity factor of approximately four to ten, and in a highly nonuniform field – point-to-plane – formed by gramophone needles with well-defined and reproducible from sample-to-sample tip curvature. Field nonuniformity factors were determined on the base of microscopic photography and field analysis. It was found that samples’ life shortened substantially in less uniform fields, with aging curves approximated by straight lines on plots with field nonuniformity factor being the logarithmic horizontal axis. As an example of insulation system life test, results for a model HV feedthrough are also given. Subscale models were subjected to 150-kV pulses at 50 Hz and collected 1.45·10
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shots through the test. This gave confidence in the design of a full-scale feedthrough with stress reduction of 25% compared to model experiments.