Current limiting spark gap for achieving arc elongation, division and

Abstract

A current limiting spark gap for use in a high voltage valve type lightning or surge arrester includes a plurality of insulating gap plates assembled together in a vertical stack to define a generally horizontally extending arc elongation and cooling chamber between adjacent plates. Series gap electrodes are disposed along opposite sides of each plate and are double electrodes formed by a unitary piece of wire preformed to slide into position onto each plate. A gap spacer is provided in each arc chamber interfitting with the series gap electrodes and the insulating plates for accurately defining and enclosing the series gap and for maintaining the spark gap as an assembly. A new and improved spark initiator with two, resilient, ionizing arms is provided in each arc chamber for consistently achieving low impulse voltage sparkover. One or more auxiliary electrodes may be provided in each arc chamber to enhance power follow current limitation by dividing the arc into two or more arc portions and by rapidly elongating and moving the arc portions to the cooling wall portions of each arc chamber. The air gaps in each arc chamber formed between the gap electrodes converge to first air gaps of closest electrode spacing and then diverge along extended arc surfaces of the electrodes to and beyond where the spacing between extended arc surfaces is at least equal to three times the closest spacing.