Some impulse-voltage breakdown tests on oil-treated paper-insulated cables

Data are presented on impulse-voltage breakdown values obtained on oil-treated paper-insulated cables over the insulation thickness range from 0.187 inch to 0.600 inch. The average stress at breakdown approximates 1,600–1,700 volts per mil. High-density papers show some superiority over ordinary-density papers. Cathode-ray oscillograms of the testing wave (1½x40 impulse wave — positive polarity) before and at breakdown are included for a typical test.