Study on the electrical strength of distribution insulators under steep front, short duration pulse

To compare the insulation characters of different distribution insulators under steep front short duration (SFSD) pulses, SFSD pulses are generated and applied on 5 selected kinds of typical 15 kV insulators. The generated SFSD impulse in this study has a 60 ns front and less than 200 ns tail. In order to measure the critical flashover (CFO) voltage under SFSD pulses, an up and down method, as in lightning impulses, is developed and used. The CFO voltage and V-t characteristics for all 5 kinds of 15 kV insulators are evaluated under dry and wet conditions with both negative and positive polarity impulses. In order to study the added insulation strength by a wood crossarm and to compare the results, all the above-mentioned tests are performed again with the 15 kV distribution insulator plus a 0.5 foot and later 1 foot wood crossarm.