Electricity: electrical systems and devices – Discharging or preventing accumulation of electric charge
Patent
1999-03-04
2000-06-06
Fleming, Fritz
Electricity: electrical systems and devices
Discharging or preventing accumulation of electric charge
361213, H01H 322
Patent
active
060726849
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a device and process for the protection of a site against lightning strikes.
It is particularly applicable to protection of buildings and sensitive sites such as storage sites, military sites, strategic antenna areas, petrochemical complexes, laboratories, pyrotechnic plants, and nuclear power stations.
2. Discussion of the Background
Protection against lightning strikes usually makes use of two devices that have been known for a long time, namely lightning arresters and a metal meshed cage. The efficiency of the lightning arrester, which channels the electrical discharge of the lightning away from a given point, is debatable. Furthermore, the protection radius of a lightning arrester is usually limited.
This is also the case for the meshed cage which, like a Faraday cage, must fully surround the site to be protected and therefore can only be used for a single building.
Furthermore, it is observed that a meshed cage is used especially to provide protection against electromagnetic aggression which is an indirect effect of a lightning strike.
Document FR-A-2 528 584 also describes a storm detection device. The device described in this document makes use of the difference in the electric field on the ground during fine weather and under stormy conditions to detect and signal when a storm is imminent. However, the device cannot detect a lightning strike or predict its effects.
Documents EP-A-320 358 and JP-A-04 160 799 describe these devices that protect a site against lightning strikes or artificially provoke a discharge.
SUMMARY OF THE INVENTION
A first purpose of this invention is to propose a protection device and a process providing protection against lightning strikes that can provide efficient protection over a large site.
Another purpose of the invention is to protect the site not only against the direct effects of lightning related to the strike, but also against indirect effects related to electromagnetic radiation.
Finally, one purpose of the invention is to propose a device capable of reinforcing the action of a conventional lightning arrester and to complement the action of the mesh cage.
Another purpose of the invention in order to achieve the objectives mentioned above, is a process for providing protection of a site against lightning strikes, characterized in that at least one ionized channel is formed in the air in the vicinity of the said site, to direct the lightning towards a lightning conductor.
In the meaning of the invention, a protected site is a site for which the characteristic dimensions are between a few tens of meters and several hundreds of meters.
Furthermore, it is considered that the ionized channel is formed in the vicinity of the site when it is at a distance of between a few tens of meters and a few hundreds of meters or even a few kilometers, from the site. The distance between the channel and the site is advantageously adjusted to suit the degree of protection and the required type of protection. When the ionized channel is close to the site, the site is well protected from direct lightning strikes. Conversely, an ionized channel further away provides better protection against indirect electromagnetic effects.
For example, this type of site may include a number of buildings or different equipment to be protected.
For example, the ionized channel may be created by a laser triggered in response to the detection and variation of an electric field on the ground, which is a precursor to the electrical lightning discharge. Due to the ionized channel, the electric lightning discharge follows the preferred path along the ionized air to join the lightning conductor provided for it.
In this respect, note that the electrical discharge corresponding to lightning usually originates in a cloud, for example a cumulo-nimbus cloud, and propagates towards the ground at an average speed of the order of 10.sup.5 m.s.sup.-1. This discharge originating in the cloud will be referred to throughout the rest of the t
REFERENCES:
patent: 4017767 (1977-04-01), Ball
patent: 5175664 (1992-12-01), Diels et al.
patent: 5726855 (1998-03-01), Mourou et al.
Patent Abstracts of Japan, vol. 17, No. 334 (E-1387), Jun. 24, 1993, JP 05 041289, Feb. 19, 1993.
Berlandis Jean-Pierre
Clement Michel
Eybert-Berard Andre
Commissariat a l''Energie Atomique
Fleming Fritz
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