| 摘要 |
<p>PROBLEM TO BE SOLVED: To increase a discharge voltage to cause hard generation of a short circuit by making an air gap at the end of an insulation cover larger than the air gap at the part other than the end of the cover. SOLUTION: A cover is constituted by an end part 3, a center part 4 and a slanting part 5. As an air gap between the cover and a conductor 1 is larger, a break down voltage is higher and, for the same air gap, a short circuit occurs at lower voltage in a discharge at two air gaps between the conductor 1 covered by the cover and the end of the cover 3 than a discharge along the surface of the cover. Therefore, if the air gap between the end of cover 3 and the conductor 1 is made larger than the air gap between the center part 4 and the conductor 1, a short circuit when a live line contacts the end of cover 3 is prevented and the whole size of the cover can be reduced.</p> |
