In electric power transmission, a 'flashover is an unintended high voltage electric discharge over or around an insulator, or arcing or sparking between two or more adjacent conductors.A flashover is the near simultaneous ignition of all combustible material in an enclosed area.Flashover occurs when the majority of surfaces in a space are heated to the point (known as fire point) at which they give off flammable gases that are hot enough to sustain combustion. Flashover normally occurs at 500 °C