Probable Outages of Shielded Transmission Lines

Based on the observed phenomenon that flashover of transmission-line towers provided with 2 overhead ground wires occurs only when the product of tower footing resistance and tower surge current exceeds the insulation strength, the probable outages that will occur on a line can be obtained by a simple method. Only those factors enter into the calculations which have become generally accepted quantitatively. Computations have been made for 3 transmission lines and the results compared with operating records. The agreement has been very good.