Abstract
Pressure signal and discharge light from tree channel were simultaneously observed when 50kV pulses (50ns in width) were repeatedly applied to an epoxy block with point-plane electrodes. The positions of pressure sources were measured from the propagation time of pressure wave from the source to an AE sensor which was located on the back of the plane electrode. The tree length estimated from the pressure signal was in good agreement with the length estimated from the discharge light. The height of the pressure signal due to the induced charge on the plane electrode tended to increase with increasing the number of the voltage application for both polarities. The pressure signal due to the volume expansion of the tree became larger by the successive voltage application in the negative point, while it became smaller in the positive point. The difference between the polarities could be explained by the effect of the residual charge near the point electrode.
