The proposed humidity correction factor of positive DC breakdown voltage of sphere-sphere gap At h/δ Lower than 13 g/m3

This paper proposed the humidity correction factor for positive DC breakdown voltage of sphere-sphere gap and compared with IEC 60052:2002 and IEC 60-1:1989 . The breakdown voltage was obtained by the ldquosuccessive discharge testrdquo method. The result of breakdown voltage was shown by relationship between DC breakdown voltage and the ratio of the absolute humidity to the relative air density (h/delta). In this paper, the proposed humidity correction factor was computed when h/delta was lower than 13 g/m³ which was the common atmospheric condition in Thailand, ranging from 7-13 g/m³. This was proven by the atmospheric condition data collected by Thai Meteorological Department in the last 6 years, 2002-2007. The experiment was done in open actual condition, assuming the atmospheric condition took some time to change. The diameters of the sphere were 5 cm and 12.5 cm and gap distance was in the range of 1.0-3.5 cm. This present work was limited by the maximum voltage of 100 kV. The number of voltage applied to the test gap to obtain each value of breakdown voltage was 10 times. Results found that the average humidity correction factor obtained from spheres 5 cm and 12.5 cm in diameter was 1 + 0.005 *(h/delta-8.5).