An evaluation of added critical flashover voltage by fiberglass crossarm to suspension insulators

Results obtained from lightning impulse measurements on fiberglass crossarms alone and with three porcelain suspension insulators are examined. The ratio of critical flashover (CFO) voltage under wet and dry conditions for fiber-glass crossarm is fairly consistent, and for crossarm with porcelain suspension insulators it is equal to 0.94. The CFO voltage added by fiberglass crossarms 0-2 ft in length to that of porcelain suspension insulators is 130 kV/ft for dry conditions and 100 kV/ft for wet conditions. For fiberglass crossarms 2-4 ft in length, the CFO voltage added to that of the porcelain string under dry conditions is 150 kV/ft and under wet conditions is equal to 140 kV/ft