This chapter discusses the effects of incident lightning scores on transmission line towers or ground wire, relying on experimental and theoretical research carried out by Gary, Garabedian, Zhang, Cristescu, and Enache. Results of their research indicated that when a lightning surge impacts a tower or ground wire, the resulting overvoltage is identified in its having a considerably shorter fail than the induction lightning surge. Their study also indicated that the back flashover voltage regarding the withstand level of insulator strings is much higher than that expected from conventional limit resulting from the standard impulse of lightning test surge characterized by durations of 1.2/50 µs.