Electrical treeing in solid polymeric insulation is physical evidence of internal damage and ultimately leads to equipment failure. This study considers the effect of frequency on treeing breakdown times in epoxy resin between 50 Hz to 450 Hz. The tree structures generated from 50 to ~250 Hz were filamentary, had narrow channels and spread throughout the insulation. Tree structures generated from ~250 Hz to 450 Hz were darker, having wider channels and less branching. The rate of tree initiation and propagation increases with increasing frequency, resulting in reduced time to breakdown. This has implications that harmonics in AC and DC networks require careful management to ensure insulation reliability is not compromised.
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