Inhomogeneous field breakdown in GIS-the prediction of breakdownprobabilities and voltages. II. Ion density and statistical timelag

For pt.I see ibid., vol.3, no.3, p.923-30 (1988). An improved model for the calculation of statistical time lags in SF₆ insulated electrode arrangements for positive impulse voltage is presented. On the basis of physical considerations, the production rate of initial electrons is ascribed to the local density of negative SF₆ ions and to field dependent electron detachment. Values of negative ion densities are measured directly, while the detachment coefficient is determined by a fitting procedure to measurements of statistical time lags