Analysis of gap distance of ultra high voltage AC transmission lines in areas with altitude above 2000m

Abstract

Abstract Research on long-wave front discharge characteristics of lines and long gaps of substation equipment in high-altitude areas needs to be conducted in a systematic manner immediately in order to guarantee the safety and economy of high-altitude UHV lines with respect to external insulation. However, at present, the gap discharge test of transmission lines is mainly carried out in areas below 2000m above sea level. The actual test is challenging to conduct in the high altitude region, and the test data is incomplete. To further confirm the validity of extrapolation of existing altitude test data to high altitude areas, this paper conducts theoretical analysis based on the real test data under standard meteorological conditions provided by GB/T 24842 standard. The altitude correction methods in IEC 60071-2: 2018 and IEC 60060-1: 2010, the m-coefficient method and g-parameter method, are used to correct the lightning impulse, power frequency, and standard switching impulse of AC transmission line gaps. The discharge voltage in areas below 5000m above 2000m is obtained, and several significant discharge characteristic parameters are obtained. Based on the 50% discharge voltage requirements of various voltage types of 1000kV transmission lines, combined with the discharge voltage curves at multiple altitudes, the minimum air gap distance of transmission lines at the altitude of 2000m-5000m is obtained. The comparative analysis of the correction results of the two methods provides a way of thinking for the next step to carry out the true test of UHV AC transmission line gap discharge in higher elevation regions.