Action volume ratio: a method to classify the danger of lightning in any given volume
Date
2015-05-07
Authors
Dickson, Andrew Stuart
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Abstract
The annual number of injuries and fatalities from lightning has, over the last century,
been on a steady decline. This is primarily due to urbanisation and movement away
from agriculturally intensive activities. In countries with a high urban population, the
incidence of lightning fatalities is below 1 death per million people per year. However,
in countries with a larger rural population, this rate is signi cantly higher, ranging
between 8 and 15 deaths per million people per year. There has been a large drive
towards educating the general public about the dangers of lightning and methods to
avoid being in a dangerous situation. However, fatal lightning events still occur on a
regular basis.
There are currently no methods to determine the risk of lightning to living beings in
open spaces. The international standard (IEC 62305-2) provides a method for the
assessment of risk to living beings within a structure, and up to three metres outside
of it. Considering that the majority of deaths by lightning occur outdoors, a method
of determining these risks is necessary.
The Action Volume Ratio (AVR) is proposed as a new method for the analysis of the
danger of lightning in any volume. It considers the dangers of all lightning injury mechanisms
in relation to the objects in the space, which are assumed to be the preferential
points of strike. A union of the dangerous volumes is then formed, and a ratio to
the total volume is created. The AVR uses accepted electrical engineering equations
to determine the dangerous areas, and places no reliance on probability theory, which
can, in many cases, skew the results of a lightning risk analysis process. The AVR can
be combined with lightning ground
flash density data to indicate the incidence and
frequency of dangerous events within a given volume.