Abstract
The authors have conducted research to clarify the manner of lightning attachment on a power distribution line and nearby tree, in order to develop effective lightning protection measures. In the previous papers, discharge characteristics were examined by the application of impulse voltages to a rod electrode when an open wire on as an overhead ground wire was placed in the vicinity of a certain type of conifer tree. This time, we investigated how the sparkover status changes when applying a lightning impulse waveform to three kinds of trees: a conifer tree, a deciduous broadleaf tree, and an evergreen broadleaf tree. The results showed no significant difference in either the status or the rate of sparkover, regardless of the kind of tree. Further, we observed the sparkover status using a 3.5 m tree model composed of a sphere electrode and resistance, instead of a live tree, placed near an open wire. Through the experiment using the model, it was found that the equivalent resistance of a 3.5-meter live tree was in the range of 100kΩ to 200kΩ.
