AC flashover performance of a horizontal insulator string under heavy icing conditions

Summary

The amount of ice formed on an insulator string plays a key role in the electrical strength of ice-covered insulators. The ice-flashover strength of horizontal strings is significantly higher than I- and V-strings because ice cannot fully bridge the gap between insulators. In this paper, the electrical strength of a horizontal insulator string under heavy icing condition and under AC voltage was investigated. Glaze ice that leads to the least amount of electrical strength of an ice-covered insulator was used in tests. It was deposited on a horizontal string placed in a cold climate chamber equipped with high voltage test facilities. Due to improved ice-flashover strength of a horizontal string compared to I- and V-strings for the same ice accumulation conditions as well as a limitation on applied voltages in the cold climate chamber, a string formed by three disks and highly conductive water of 222 µS??cm was applied to generate flashovers on the horizontal string. By adding sodium chloride (NaCl) to deionized water, the desired conductivity was obtained. The pneumatic spray nozzle system sodium was fed with this water. “Melting regime” test procedure of IEEE Std. 1783 that simulates service conditions of insulator flashover was used to assess the flashover performance of the test insulator. In addition, a static arc model was elaborated for estimation the minimum flashover voltage (VMF) of a string placed in various positions: vertical, inclined and horizontal where it was validated with laboratory tests.

Additional informations

Authors

M. FARZANEH

Keywords

AC FLASHOVER PERFORMANCE, HORIZONTAL INSULATOR STRING, HEAVY ICING CONDITIONS