765-kV Transmission Line Insulation: Testing Program

The scope and results of a testing program for the insulation design of the American Electric Power 765-kV transmission lines are presented. With a 32-unit V string in the middle phase, and 30-unit V strings in the outer phases (standard 5¾- by 10-inch suspension insulators), the composite switching-surge strength of the tower is characterized by a 3-sigma withstand not less than 1250 kV or 2 pu of system voltage crest.