Influence of A. C. Test Procedure on Breakdown of Air Insulations Comparison with Switching Impulse Tests

A.C. voltage tests carried out on various air gaps prove that breakdown parameters vary with test procedure. These variations can be taken into account by using a model, in which A.C. voltage is considered, from a breakdown probability point of view, as a succession of independent cycles. Moreover, switching impulse tests show that one positive half-cycle of A.C. voltage is equivalent to a switching impulse of 3300 Ps time to crest. On the basis, then, of switching impulse breakdown characteristics of air gaps, the model gives a good evaluation of the breakdown parameters for any A.C. voltage test procedure.