Categories: Electronics

Floor strikes and lightning safety of buried cables

There was a latest lightning incident the place fifty individuals have been harm whereas standing on moist soil in the meanwhile of a close-by lightning strike that triggered {an electrical} present to circulate by means of the bottom. Seven individuals have been hospitalized however happily, there have been no fatalities.

The incident raises a degree that I’ve seen made as as to if overhead energy strains are extra inclined or much less liable to lightning strike harm than buried energy strains.

The problem just isn’t so simple as some would have you ever imagine.

Think about the next picture in Determine 1.

Determine 1 An elevated energy line and a lightning strike the place the ability line is remoted from the moist soil present. Supply: John Dunn

Aside from a direct strike to the ability line itself (I as soon as noticed that very factor occur however that’s a separate story), an overhead energy line is just about remoted and protected against the moist soil’s present paths.

Nevertheless, if the ability line is buried, the moist soil’s present paths can impinge on the ability line very a lot in the identical the way in which as lightning currents impinged on these fifty individuals (See Determine 2).

Determine 2 A buried energy line and a lightning strike the place the ability line is subjected to the moist soil present. Supply: John Dunn

It has been urged sometimes that energy line burial is a assured approach to defend any energy line from a lightning occasion. That will or will not be true relying on many circumstances, however energy line burial is NOT an absolute panacea, not by any means.

Soil composition, the presence or absence of close by constructions, the presence or absence of water mains, numerous lightning arrestor preparations, greenback expenditures for excavation efforts, and so forth should all be assessed by consultants of which I most undoubtedly am NOT.

Within the midst of many buildings—many tens of tales tall—throughout the borough of Manhattan, New York Metropolis, many energy strains are positioned under floor, beneath all types of concrete and asphalt. Within the borough of Queens, nonetheless, the place I grew up (Rego Park to be exact); overhead energy strains are discovered far and wide.

There aren’t any easy solutions and no clear-cut conclusions. Relatively, this essay’s objective is merely to dispel any simplistic serious about the difficulty.

John Dunn is an electronics guide, and a graduate of The Polytechnic Institute of Brooklyn (BSEE) and of New York College (MSEE).

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