PD patterns and current shapes of artificially-simulated tree channel

In order to clarify PD mechanism and degradation of electrical tree in solid polymer insulator, PD patterns, pulse sequences and current shapes in an artificially simulated tree channel were investigated. A few hours after voltage application, new tree channels started to propagate. When they were propagating, the voltage increment between two consecutive PD pulses was constant in positive polarity in spite of PD magnitude changing. Furthermore, there were at least two types of PD current shapes in the same positive half cycle. This result suggests that there are different mechanisms of PD's in the same half cycle.