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Feb 01

Février 2013 – SEFTIM a décider de favoriser le développement du concept de point de capture sensible au champ électriqueFebruary, 2013 – SEFTIM decided to promote the development of the sensitive capture point to electric field.

Suite a sa participation dans les comités scientifiques et les conférences sur la foudre (notamment ICLP), SEFTIM a décider de favoriser le développement du concept de point de capture sensible au champ électrique.

Quelles sont les alternatives aujourd’hui pour la protection des bâtiments selon les normes 62305

La cage maillée

Les paratonnerres type PTS bien adapté à la protection de structures de petite dimensions ou de certains points sensibles sur une structure de plus grande dimensions.

Cependant, un paratonnerre est connu pour avoir son efficacité qui dépend de nombreux paramètres notamment son rayon de courbure et l’emplacement où il est installé. L’emplacement détermine le champ électrique présent et donc l’efficacité de ce PTS. Dans la normes, tous les PTS se valent et leur efficacité n’est jamais réellement démontrée. Cependant, on sait aujourd’hui que ce n’est pas vrai. Il y a beaucoup de littérature sur le sujet, par exemple les écrits du Dr. Risk « F.A.M. Rizk, « Modeling of Lightning Exposure of Sharp and Blunt Rods » IEEE Trans. On Power Delivery, Vol. 25, No.4, pp 3122 -3132, October, 2010″ scientifique célèbre dans le domaine de la foudre. On peut également se reporter aux essais en vrai grandeur réalisés par le Dr. Moore aux USA.

Le Dr. Risk, déclare à ce sujet : « When Ben Franklin first invented the lightning rod, he didn’t think that they would get hit by lightning. He thought that placing needle sharp iron rods at the tops of buildings would prevent lightning from happening. Of course that didn’t work, but when he observed that his grounded rods were being struck but safely conducting the lightning current to ground, he recognized that this was a good thing. But Ben Franklin had no idea how his lightning rods worked and his choice of using sharp tipped rods had no connection with the phenomenon he had accidentally uncovered. In recent years there have been some major developments in our understanding of the physics of electric discharges and specifically how grounded objects interact with lightning. Previously unexplained phenomena like sharp and blunt rods occasionally being bypassed by lightning and tall structures getting struck well below the top have now been addressed in published, peer reviewed papers in one of the most reputable scientific Journals. »

Il y a donc des formes qui sont plus efficaces que d’autres et des emplacements qui sont plus pertinents que d’autres. La société Lightning Electrotechnologies au Canada s’est spécialisée dans une telle optimisation (lightningelectrotechnologies.com). Dès lors qu’un site sensible doit être protégé, SEFTIM peut mettre à disposition ces moyens de calcul pour positionner idéalement le paratonnerre. Cette approche est entièrement conforme aux normes 62305 (il ne s’agit pas de paratonnerres actifs).Following to its participation to the scientists comities and meeting about lightning (especially ICLP), SEFTIM decided to promote the development of the sensitive capture point to electric field.

What are the today’s alternative to buildings’ protection according to the 62305 standard.

The meshed cage

The PTS type lightning rods are well adapted to the protection of small size structure or some critic points on a bigger size structure.

Nevertheless, a lightning rod is known having its efficiency depending on several parameters as its curve radius or its installation location. The location cause the actual electric field and therefore the efficiency of this PTS. In the standard, every PTS are equal and there efficiency has never been really demonstrated. However, we know on this day that it’s not true. There is a lot of literature on this subject, for example the publications of the Dr. Risk Risk « F.A.M. Rizk, « Modeling of Lightning Exposure of Sharp and Blunt Rods » IEEE Trans. On Power Delivery, Vol. 25, No.4, pp 3122 -3132, October, 2010″ famous scientist on the lightning field. We can also refer to the live—size experimentation realized by the Dr Moore in the USA.

The Dr. Risk declare about this : « When Ben Franklin first invented the lightning rod, he didn’t think that they would get hit by lightning. He thought that placing needle sharp iron rods at the tops of buildings would prevent lightning from happening. Of course that didn’t work, but when he observed that his grounded rods were being struck but safely conducting the lightning current to ground, he recognized that this was a good thing. But Ben Franklin had no idea how his lightning rods worked and his choice of using sharp tipped rods had no connection with the phenomenon he had accidentally uncovered. In recent years there have been some major developments in our understanding of the physics of electric discharges and specifically how grounded objects interact with lightning. Previously unexplained phenomena like sharp and blunt rods occasionally being bypassed by lightning and tall structures getting struck well below the top have now been addressed in published, peer reviewed papers in one of the most reputable scientific Journals. »

So, there is more efficient forms and locations more relevant than others. The company Lightning Electrotechnologies from Canada is specialised in thekind of optimisation (lightningelectrotechnologies.com). As soon as a critic area has to be protected, SEFTIM can make this calculation means available to ideally locate the lightning rod. This manner is completely conform the 62305 standard (it’s not about ative lightning rod).