The CFO voltage and V-t characteristic of 15 kV power distribution insulators are important factors in insulation coordination design of power distribution systems. Insulation designs for distribution feeders are usually based on 1.2/50 mus lightning impulse, while insulator behavior under steep front short duration (SFSD) pulses is not concerned. The generated SFSD impulse in this study has a 60 ns front and less than 200 ns of the tail. The insulators are evaluated under dry and wet condition with both negative and positive polarity impulses