抄録
We have investigated sparkover characteristics when direct lightning hits on power distribution lines to which trees exist in close proximity. In the previous study, negative lightning impulse voltages were used to understand sparkover characteristics when an open wire of overhead distribution line was placed in close proximity to a tree. The rate of sparkover to the open wire or to the open wire via the tree was examined and pre-breakdown phenomenon was observed in detail.
This paper describes experimental results that different voltage waveforms (lightning impulse and switching impulse) were applied under the condition that an open wire was placed in close proximity to a tree. Regardless of impulse voltage waveforms, sparkover occurring directly on the open wire could be seen, even when the height of the open wire is equal to that of the tree or the open wire is about 0.5m lower than the tree. In addition, the progress of an upward leader from the open wire is faster than that from the tree. We investigated the attachment manners when the open wire was placed in close proximity to a log instead of the tree. It was found that the attractive effect of the log was stronger than that of the tree.
