Statistical relations of breakdown voltage and the parameters characterizing predischarge phenomena at a short vacuum gap

A statistical relation between breakdown voltage and the parameters characterizing the predischarge state at a short vacuum gap is discussed. The three following parameters were chosen: a voltage which causes an emission current of a measurable value (equal to 10/sup -6/ A), an electron field emission current measured at a selected voltage value, and the electric field amplification factor determined from the Fowler-Nordheim equation. For all the investigated relations, a regression analysis was carried out and the coefficient of determination was evaluated. Plane electropolished electrodes made of Cu and special electrodes made of Cu-Cr sinter used in a vacuum interrupter were investigated. All the relations studied prove that the three parameters can be treated as criteria for evaluating the electroinsulating properties of a short vacuum gap.