Experimental method of electrical tree initiation in polymer under high voltage nanosecond pulses

The point-plane geometry with iron electrode system was employed in the electrical tree initiation experiment under high voltage nanosecond pulses, with both single and multiple needle electrodes. The result of the latter electrode scheme has a good correlation with that of the former, with higher efficiency at the mean time. Electrical tree initiation experiments were done by the step-up method and accumulation method at different frequencies, and the initiation characteristics of polystyrene were derived. The initiation voltage drops as the pulse frequency rises up from 50 Hz to 500 Hz, while it increases as the frequency rises in the range of 500 Hz to 800 Hz. Aging experiments for different pulsed power utilities were also designed.