Electroluminescence from epoxy insulation under impulse voltage

Light pulses have been recorded during the application of positive and negative unipolar surges to epoxy insulation containing a needle-plane electrode structure. It is shown that the light pulses occur more frequently on the rising and falling edges of the surge waveform, which indicates space-charge formation. The lack of light pulses, and presumably of energetic charge injection, at very high surge repetition rates was noted