Analysis of Gap Distance Selection and Altitude Correction for 1000kV AC Double Circuit Line with the Same Tower in the Area of Altitude 4000m and Above

In high altitude areas, if the air gap of the external insulation equipment is too small, breakdown or flashover accidents are likely to occur, and if the air gap is too large, it will result in waste of investment, so it is important to reasonably determine the level of the external insulation of the 1000kV AC double circuit line with the same tower in the high altitude area to ensure the reliability of the local power transmission and the economy. In this paper, based on the test results of the discharge characteristics of the tower gaps of existing same-tower double-circuit transmission lines at low altitude areas, and by adopting the altitude correction method recommended by IEC 60071-2:2018, the analysis and research on the correction of the industrial frequency and standard operating impulse voltage of 1000kV AC same-tower double-circuit lines in the areas of 4000m above sea level have been carried out. The frequency and operational impact discharge voltages of 1000kV AC same tower double circuit line tower gaps in the range of 4000-5000m above sea level were obtained, and the required gap distances for different types of voltage cases were recommended, and the results of the study can provide ideas for the design of the insulation coordination of 1000kV AC same tower double circuit line towers in areas of 4000m above sea level and above.