Contribution to evaluation of lightning-impulse voltage parameters with superimposed overshoot in airgaps

The distributed inductances of high-voltage testing circuits, which grow with geometrical dimensions and rate voltages of the equipment under test, could cause natural oscillations or superimposed overshoot on the impulse voltage crest and then the insulation under test can be submitted to distorted weaves instead of standard impulse. Before the introduction of computer aided calculation of digitally recorded lightning impulses, the calculation of the higher value of impulse was made drawing a mean curve across oscillations on the recorded voltage curve. With that method the reproducibility of the test was frequently doubtful. The introduction of the test voltage factor in IEC 60060-1 Ed. 3 has been an important step to assure reproducibility and traceability for high-voltage testing with…