Testing non-uniform gaps with oscillatory switching surges

With oscillatory switching surges, breakdown across non-uniform gaps occurs at relatively low electric stresses. If the surges are uni-directional, then there is a pronounced polarity effect, the positive surge having the lower value. For each gap spacing there will be an oscillatory frequency which results in a lower voltage failure. The decay rate of the surge will affect the breakdown voltage. With a slow decay rate the voltage would generally be lower. With bi-directional surges failure will occur when the high stressed zone is positive, provided the decay rate is not too great