ABSTRACT

The study of lightning predates electric power systems by many centuries. Franklin and others established the electrical nature of lightning, and introduced the concepts of shielding and grounding to protect structures. The first return stroke from the direct termination of a negative, downward cloud-to-ground lightning flash is the dominant risk to power system components. A traditional indicator of cloud-to-ground lightning activity is given by thunder observations, collected to World Meteorological Organization standards and converted to Ground Flash Density. Electromagnetic signals from individual lightning strokes are unique and have high signal-to-noise ratio at large distances. Lightning mitigation methods for transmission lines need to be appropriate for the expected long-term ground flash density and power system reliability requirements. Direct lightning strokes to any overhead transmission line are likely to cause impulse flashover of supporting insulation, leading to a circuit interruption. Insulator dry arc distance has a remarkable effect on the lightning performance of transmission lines.