Abstract
A new methodology, the Collection Volume Method, is given for the
placement of lightning rods or äir terminals" for the protection
of structures against lightning. Each air terminal is assigned an
ättractive radius", which is calculated as a function of its height,
radius of curvature, location on the structure, structure dimensions,
and a set of site, atmospheric and lightning-related parameters.
In a similar manner, an attractive radius is assigned to all "competing
features" on the structure which can also capture a lightning strike,
e.g., building edges, corners, parapets, flagpoles, lift motor rooms,
etc. The calculations of the attractive radii also depend on the
upward leader inception criterion employed, in the present case a
critical breakdown field of ~ 3 MV/m over an effective space charge
or corona radius of ~ 0.3 m, both taken from laboratory experiments
of previous investigations. The attractive radius computations involve
three-dimensional calculations of the electrostatic field on the
surface and immediately around the structure, i.e., the degree of
electric field intensification created by the penetration of the
structure into the ambient field of the thunderstorm. The structure
is regarded as being protected if the combined attractive areas of
the various air terminals overlap those of the competing features.
The Collection Volume Method is shown to be a new, practical, physically
based technique for the efficient placement of air terminals on structures.
It can both complement and replace existing placement methods as
the need arises.
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