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Aerial bundled cables (also aerial bundled conductors or simply ABC) are overhead power lines using several insulated phase conductors bundled tightly together, usually with a bare neutral conductor. This contrasts with the traditional practice of using uninsulated conductors separated by air gaps. The main objections to the traditional design are that the multiple conductors are considered ugly, and external forces (such as high winds) can cause them to touch and short circuit. The resultant sparks have been a cause of bushfires in drier climates. In the UK where some supplies to rural property are converted to PME/MEN from TT Earthing system concerns have been expressed that the lower conductor alone may be broken, (by high vehicle or falling tree for example) but with the upper phase conductors intact. This is a potentially dangerous fault condition. With ABC, a simultaneous disconnection of all conductors is more likely. In moister climates, tree growth is a significant problem for overhead power lines. Aerial bundled cables will not arc over if touched by tree branches. Although persistent rubbing is still a problem, tree-trimming costs can be reduced. Areas with large trees and branches falling on lines are a problem for aerial bundled cables as the line degrades over time. Due to the very large strain forces cracking and breaking insulation can lead to short circuit failures which can then lead to ground fires due to dripping of molten insulation. == Advantages == * Relative immunity to short circuits caused by external forces (wind, fallen branches), unless they abrade the insulation. * Can stand in close proximity to trees and will not generate sparks if touched. * Simpler installation, as crossbars and insulators are not required. * Less cluttered appearance. * Can be installed in a narrower right-of-way. * At junction poles, insulating bridging wires are needed to connect non-insulated wires at either side. ABC can dispense with one of these splices. * Less risk of a neutral-only break from tree or vehicle damage, increasing safety with TNC-s systems. * Electricity theft is made harder, and more obvious to detect. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Aerial bundled cable」の詳細全文を読む スポンサード リンク
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