Effect of Humidity and Temperature on the DC Breakdown at different tip angles of Rod-Rod Gaps

According to IEC 60-1 (1989), the maximum humidity which is accepted under DC breakdown in the standard is only 13 g/m³. However, in Thailand, the humidity is mostly higher than 13 g/m³ . Therefore, this paper deals with experimental study of breakdown characteristics of air-gap which is strongly affected by atmospheric conditions such as temperature and humidity under DC voltage. The humidity in the present work is in the range of 13-20 g/m³. It will be interesting to see how the breakdown characteristic under DC voltage will change under high humidity. Three different tip angles, 30deg, 45deg and 60deg, of the rod-rod gap with the range of 2-12 cm were used to investigate the effect of the atmospheric condition. All test electrodes were made of copper with the symmetrical shape. The breakdown voltage was plotted as a function of the gap distance at different humidity values. Finally, it can be seen that the humidity factor K_h in IEC 60-1 is an important factor for the breakdown in the rod-rod gap under DC breakdown