Switching Surge Operating Duty of Lightning Arresters

After mentioning different methods of testing the ability of an arrester to discharge long-duration switching surges, the artificial line discharge test with applied power frequency voltage is discussed. Oscillograms show that voltage transients during such tests may be influenced by the series gap of the test circuit. Test results agree fairly well with curves obtained from digital computations. Hence it appears justifiable to investigate by digital computations alone how test results are influenced by varying certain test- circuit parameters and the rate of rise of the arrester arc voltage. Computations were made for a 525-kV line and a modem 80 percent arrester. Particular mention is made of the disadvantage that could arise from too high a rate of rise of the arc voltage and of the fact that short lines can, in certain cases, impose a heavier duty on an arrester than longer lines.