Switching Surges Insulation Coordination: Switches, "Anomalous" Sparkovers, and Possible Generalization

The authors examine the problem of coordination between the open-gap insulation of a switch and its insulation-to-ground, with respect to switching surges. The results of a series of tests performed on an EHV switch with varied gap spacing and varied stack height are examined, and a method for designing the open gap of a switch is accordingly proposed. From the same point of view, "anomalous" flashovers are criticized. After having examined the results of a series of preliminary tests performed on rod-rod and rod-plane gaps with different clearances from grounded structures and vertical planes, a practical approach to the problem of eliminating anomalous flashovers is submitted. However, the need for better physical knowledge of the discharge mechanism for long-fronted impulse waves is emphasized.