The nature of divergent-field surge-voltage endurance in epoxy resin

An experimental study has been conducted to quantify the voltage endurance of electrical grade epoxy resin insulation when subjected to pulse voltages in a divergent field. Voltage endurance has been quantified as a function of pulse width, repetition rate, and polarity. Supporting measurements of free radical generation have been made by electron paramagnetic resonance (EPR), and the progress of the aging mechanism tracked by sensitive photonic emission measurements. The results suggest (at least for positive polarity) that estimates of endurance under pulse voltage conditions can be made from conventional power frequency data, However, it is shown that a correction is necessary to allow for the effects of waveform, and a theory is advanced for that purpose.