New challenges in lightning impulse flashover modeling of air gaps and insulators

Lightning overvoltages were causing problems on overhead lines well before Tesla and Edison argued over the merits of ac and dc. Many of the overvoltage protection methods for distribution lines follow the same philosophy as that used for telegraph and telephone lines. Modern guides for improving distribution-line lightning performance, such as IEEE 1410, still distinguish between unpreventable outages caused by direct flashes to phase conductors and preventable faults that are caused by flashes to objects or the ground near the line.