Abstract
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 <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">U</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">50</sub> 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 <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">U</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">50</sub> 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/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> 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; <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">U</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">50</sub> varies within 1.0%-1.15% range with per g/m increase of absolute humidity.
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