Estimation of Charge during a Lightning Flash Using Electric Field Measurements

1 INTRODUCTION Electric power utilities have sustained significant damage from lightning. The occurrence of line faults is one result of lightning damage. To prevent it, power utilities adopt various measures of protection from lightning. Transmission line overhead ground wires greatly contribute to a decrease in the number of line faults by preventing direct hits to the power lines. Lightning that contains a large amount of current raises the potential of the tower although the ground wire prevents direct hits to the power line. As a result, back-flashover may be generated on transmission line insulators, and power failure can occur. It is possible to specify the fault point by using the observed data along with a Lightning Location System (LLS), as back flashovers tend to be generated by the large current lightning events. However, LLS data is not effective in locating damaged equipment parts. For instance, the ground wire sometimes sustains damage when a strand breaks as a result of its role of preventing direct hits to the power line. Figure 1 is a photograph of a ground wire that was damaged by lightning, Shimizu et al. (2006). To ensure reliability, public security and a consistent power supply, the electric power utilities should strive to locate damaged wires immediately, and take appropriate action. it is clear that the probability of damage to the shield wire is greatly dependent on the amount of charge contained in a lightning flash. It is difficult