Improving insulator reliability with insulating barriers

When an insulating barrier is set up on an insulator with an inner electrode, suppression of negative surface leaderlike discharge and increase in AC flashover voltage are observed over a range of barrier distance (the distance between the HV electrode and the barrier) of ≲15 mm (critical value). When the barrier distance is longer than the critical value, a punch-through breakdown of the insulator near the junction of the barrier and the insulating surface sometimes occurs. This punch-through breakdown voltage is much lower than the AC flashover voltage for the insulator without a barrier