PRINCIPLE

A rod - type lightning conductor, connected to earth, efficiently works by altering, at its level, the equipotentials which match the structures of the building it protects. The emergence of the lightning conductor is an important factor in increasing the local electric field. The principle of the piezoelectric lightning conductor designed by Franklin France relies on several factors: the reinforcement of the local electric field and the early creation of a preferential discharge channel.

OPERATION

PIEZOELECTRIC STIMULATION
The basic principle of the Saint-Elmo lightning conductor is to increase the number of free charges (ionized particles and electrons) in the air surrounding the lightning conductor and to create, within a cloud-ground electric field, a channel of high relative conductivity constituting a preferential path for lightning.

Free charges are created by the corona effect by applying on the Saint-Elmo lightning conductor's ionized point (s) the voltage supplied by cells of piezo-electric ceramics (leadzirco-titanate); their feature is to produce a very high voltage by simply modifying the applied pressure. The Saint-Elmo lightning conductor is therefore equipped with a mechanical device that transforms the stress resulting from the wind action on the lightning conductor into a pressure stress on the piezo-electric cells.

The voltage therefore produced is applied, through the high voltage cable that runs inside the lightning conductor's support pole, onto the ionized point(s) to create, by corona effect, free charges. Then, these charges are expulsed, by the venturi system, from the lightning conductor's head, profiled on purpose (forced air circulation). When they are outside the head, these charges are submitted to the cloud-ground electrical field. The charges polarized like the cloud are repelled towards the ground, the channel of charges that forms in prolongation of the lightning conductor is then exclusively composed of charges from the opposite pole to the cloud's electric pole (it takes into account the  discharge's pole : positive or negative).

REDUCTION OF THE EXCITATION TIME OF THE CORONA EFFECT
Any artificial increase in the ionic density of the air surrounding an electrode favors a lowering of the breakdown potential.