A mechanism transition between two consecutive breakdowns at short rod-plane vacuum gap

The objective of this paper is to propose a mechanism transition between two consecutive breakdowns at short rod-plane vacuum gap. A rod-plane vacuum gap is designed in a vacuum interrupter. A 50Hz power frequency voltage is applied across the vacuum interrupter to measure the pre-breakdown field emission current. A compensation algorithm removes the displacement current from the measured current and then only field emission current left. The voltage and field emission current fit the Fowler-Nordheim theory and two parameters β value and effective emission area can be obtained. Three vacuum interrupters are applied the power frequency voltage twice and two consecutive breakdowns happen. The experimental results show that: The first breakdown (BD) voltages of the three vacuum interrupters are 49.5 kV, 44.7 kV, 41.1kV (peak value), and the β value are 260,219, 257 respectively. The second breakdown (BD) voltages of the three vacuum interrupters are 51.5 kV, 48.3 kV, 44.1kV (peak value) but pre-breakdown currents β values and effective emission area are too low to be determined. Thus a mechanism transition between the two consecutive breakdowns in a short rod-plane vacuum gap are suggested as follows: field emission current induced breakdown and particle induced breakdown both exist at 1mm vacuum gap. The first breakdown is induced by field emission current and the second breakdown is induced by particles.