d . Breakdown Voltage Test
Breakdown voltage is measured in a test tube with alternating voltage, grid frequency. As used between the electrodes with big ball between s = 2.5 mm. Test voltage is increased from zero at a rate of about 2 kV/s until breakdown voltage occurs. Twentyfive trials conducted for each penetrating oil sampling. The average value of breakdown voltage specified in the measurement cannot be less than the value specified standard. Test interval between the first breakdown voltage test with the second breakdown voltage test is 2 (two) minutes.