Positive Switching Impulse Discharge Performance and Voltage Correction of 1 meter Rod-plane Air Gap

Switching impulse discharge performance of air gaps at high altitudes, which is fundamental in the extra-high voltage external insulation design, remains the unsolved key technology across the world. Due to the limited applicable range of g parameter method, which is recommended by IEC Publication 60-1(1989), this paper aims to explore the relationship between positive switching impulse 50% discharge voltage U ₅₀ of rod-plane air gaps and atmospheric parameters, and proposes two new voltage correction methods based on parameter g and atmospheric pressure ratio respectively, which are proved by the experimental investigations carried out on 1 m rod-plane air gap both in the artificial climate chamber and at three spots of different high altitudes in this study. The results show that positive switching impulse 50% discharge voltage U ₅₀ of rod-plane air gaps is a power function of relative pressure and relative air density, taking the influence of absolute humidity into account; g parameter method in IEC Publication 60-1(1989) does not adapt to the regions with an altitude above 2000 m and under the h/delta>15 g/m³ condition; in comparison with the correction method based on g parameter, the one based on relative atmospheric pressure has a wider applicable range and less errors; U ₅₀ varies within 1.0%-1.15% range with per g/m increase of absolute humidity.