Air Gap Discharge Characteristics and Altitude Correction of 500 kV Tower at Areas Higher than 4000 m above Sea Level

Abstract

In order to ensure the reliability of 500 kV transmission project at high altitude, in this paper, the discharge characteristics and voltage altitude correction of 500 kV transmission lines air gap at high altitude areas were studied. The common insulation coordination methods and determined various factors, which influence discharge characteristics of 500 kV transmission line tower air gap at high altitude, were analyzed. In the State Grid Tibet High Altitude Test Base, lightning impulse test and switching impulse test were carried out aiming at the typical tower side phase of 500 kV transmission lines. Besides, the AC voltage discharge characteristics test of side phase line-tower window was also carried out. Then, the relationship curves of 50% discharge voltage and different gap distance were obtained. Based on the experimental data, the altitude correction factor of transmission line tower air gap discharge voltage at $4000 m\sim5500m$ altitude was studied, and the altitude correction method suitable for this altitude was put forward. The minimum air gap distance required for 500 kV transmission lines above 4000 m altitude was also recommended. Test results can be applied to the engineering design of 500 kV transmission lines in high altitude area, especially above 4000 m altitude. On the other hand, the results provide the basic data for altitude correction of long air gaps in high altitude areas.