Flashover voltage is the threshold potential at which an arc strikes between two live conductors or a conductor and earth, bypassing the intended insulation. Engineers test and rate equipment against this value to ensure insulators can withstand expected system surges, such as lightning strikes or switching transients. Exceeding this limit causes surface tracking and catastrophic failure of the air gap.
The lab results show the wet flashover voltage for these new polymer strings is well above our 132 kV requirement.
Wet flashover voltage is always significantly lower than dry flashover, which is why outdoor insulators are designed with sheds to keep parts of the surface dry.
Related terms
Flashover
Disruptive discharge over or around insulation that creates a short circuit through the air.
Creepage distance
Shortest route over an insulating surface from one conductive part to another, the dimension that resists tracking.
Insulation coordination
Sizing insulation and surge arresters together so any flashover lands at a cheap, self-restoring point, not inside plant.
BIL
Basic lightning impulse insulation level: the peak impulse voltage equipment must withstand without breakdown.