AC Pollution Flashover Characteristics and Altitude Correction of Train Roof Insulators at High Altitude

Roof insulators are essential equipment for the safe operation of the traction power supply system. When the train runs to high altitude, the roof insulator is completely exposed to the atmosphere. Affected by low air pressure and natural pollution, the insulation performance is significantly reduced, threatening the safety of train operation. Using the artificial climate simulation system, the AC pollution flashover characteristics of different types of roof insulators at an altitude of 498~4500m are studied. And the altitude correction method of flashover voltage is proposed. Finally, the follow-up research and suggestions for roof insulators at high altitude are given. The results show that the average values of the pollution characteristics impact index a of the FDZ and FS type roof insulators are 0.308 and 0.268 respectively, and the average values of the air pressure characteristics impact index <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</i> are 0.721 and 0.867 respectively. The smaller the insulator sheds spacing, the larger the proportion of air gap arc. And the lower the air pressure, the more serious the floating arc phenomenon. For every 1km increase in altitude, the average flashover voltages of FDZ and FS type roof insulators decrease by about 8.65% and 10.4%, respectively. The roof insulators with shed spacings of 30-35mm and shed combination of a large and two small are recommended at high altitudes.