Abstract
Generally speaking, lightning overvoltages on overhead power distribution lines can be suppressed more greatly for small earth resistance of an overhead ground wire, which is popularly used for lightning protection of overhead power distribution lines, than for large earth resistance.
This paper shows the possibility that overvoltages, which arise between a phase conductor and the earth, are larger on distribution lines with high earth resistance of an overhead ground wire than on those with low earth resistance of an overhead ground wire. Typical examples are demonstrated for induced overvoltages due to nearby lightning strokes as well as for direct lightning hits to distribution lines. These phenomena can be explained by the conversion of common mode overvoltages into normal mode (between a phase conductor and an overhead ground wire) ones. Although above phenomena are not ordinary, we should be careful when considering effective protection method for an overhead power distribution lines supported by wooden poles or for ones constructed in the field of low soil conductivity.
