Abstract
Theoreticl study and phenomenal examination have been done for a long time, but some electric power company even today has instataneou power failure due to the galloping. Our study differs from other ones on the point that non-linear three dimentional simultaneous equations of conductor movement can be solved directly using numerical calculation. Foundamental characteristcs of galloping can be made clear by that calculation changing parameters variously. This time, we used the method that bundle conductor are changed equivalently to single conductor. We could also make it clear that instable domain becomes wider when rotational movement of conductor occurs.