Tis article might demonstrate the complexity of an issue and shed some light
for you:
<<science>>
Summary of a recent paper co-authored by Professor Vernon Cooray is
enclosed. This is entitled, "The Franklin Lightning Conductor: Conditions
Necessary for the Initiation of a Connecting Leader".
The Paper has important implications regarding validity of ESE (Early
Streamer Emission) technology. It indicates that the artificial initiation
of streamers would not increase the striking distance of any air terminal of
practical size. This means that its protective range would not change
either.
The above conclusion applies to electrode diameters up to about 0.7 m. For
larger electrodes, the upper limit for the possible increase in the striking
distance is only about 30% when the downward lightning leader is arriving
directly above the ground object.
As the title of the paper indicates, the results are based not on the
conditions sufficient for the generation of a connecting leader, but rather
on the conditions necessary for it. Hence the stepped downward leader may
have to come even closer than the estimated values to have a successful
termination. Also, like in all lightning models, the results are based on
several simplifying assumptions.
I have a couple of comments on the above important findings:
1) The protective range is governed by a configuration in which the
downward leader is horizontally displaced from the ground object rather than
directly above it. For this governing configuration, the maximum possible
effect of artificial triggering is expected to be even less than 30%.
2) Any possible increase of the striking distance via artificial
triggering in case of the larger electrodes is negated by the fact that the
striking distance drops when size of the electrode is increased. This can
be seen from Fig. 1 of [1]. This, together with the physical and economic
impracticality of using air terminals of huge sizes lead to the conclusion
that artificial triggering is useless under all conditions.
We wish to thank Professor Aage E. Pedersen, for bringing this paper to our
attention. We also wish to thank Professor Cooray for reviewing a draft of
this message and for granting permission to use his paper.
REFERENCE:
[1] Abdul M. Mousa, "Validity of the Collection Volume Method/Field
Intensification Method for the Placement of Lightning Rods on Buildings",
Proceedings of ICLP 2002, Vol. II, pp. 809-814.
Abdul M. Mousa, Ph.D., P. Eng., Fellow IEEE
[email protected]
I took the liberty to post the copy of the document Mr. Abdul mentioned on
my own webside:
http://members.shaw.ca/arturek/science.html
Just do not get zapped ;-)
Art.
