Breakdown phenomena of rod-rod gaps under impulse voltages of opposite polarity on both electrodes

Even with geometrically symmetrical arrangements of air gap electrodes, the electrical strength of such gaps under impulse voltages is different depending on the polarity of the voltage and again different comparing electrical stress between one electrode and earth alone with stress of opposite polarity between both electrodes and earth. By detailed investigation of predischarge phenomena, physical reasons for such differences can be shown. The results are of interest for the prediction of phase-to-phase strength of air insulation as well as for problems of suitable test procedures.