Selection of insulator strings for 1150 kV AC lines under pollution conditions

摘要

1. Outdoor insulation of 1150 kV is selected for normal service conditions, i. e. for exposure of wet polluted insulators to operating voltage stresses. 2. When dimensioning insulator strings for a 1150 kV OHL, account must be taken of a number of special requirements, such as efficient use of the available creepage distance and the string length, the breakdown strength of multiple-string insulating structures, concentration on the flashover performance under pollution conditions, and optimization of insulator shape for specific pollution conditions. 3. Outer insulation levels of 1150 kV lines can be best determined on joint use of statistics and field pollution studies in the anticipated line route area, which assures the needed reliability without excessive margins. 4. State-of-the-art porcelain long-rod insulators, with a 10~(-7) annual failure rate, hold a better promise, as compared to cap-and-pin insulators, for application on 1150 kV overhead lines.