Development of tree in polymeric insulator applied successive impulse voltages and its three-dimensional measurement

Impulse trees in insulators have been measured three-dimensionally to investigate their development mechanism. Since a usually observed tree is a projected one on the plane, the projected tree has pretend branches and the directions of its branches are not exact. In this paper, the impulse trees in the polymeric insulator (PMMA) have been measured three-dimensionally utilizing a CT (computer tomography) method. Successive impulse voltages have been applied. In each step, the tree has been measured and also the properties of the tree which cannot be obtained by the projected tree, such as the cross section. The volume and the distribution of the branches have been obtained for both polarities