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Copyright © 2000, MCB UP Limited
French innovation leads to less lightning damage
French innovation leads to less lightning damageKeywords: Buildings, Safety, European Standards
Every year in France there are two million lightning strikes, killing or injuring 50 people, several thousand animals, and causing 15,000 fires. A number of French companies specialise in the design, manufacture and sale of products designed to protect against the direct and indirect effects of lightning.
Lightning conductors have been improved by incorporating ion generators. Ionising lightning conductors produce repeated pulses at their tip, without requiring an external power supply. These have the effect of encouraging an ascending discharge, as well as its propagation, during the early stages of the development of the lightning. Protel, designed the Vega ionising lightning conductor. Stephane Smadia, marketing manager at Protel, says, "Vega is a electronic ionising lightning conductor. A generator produces an emission of ions synchronised to the ascending tracer. This generator, placed in a sealed double metal-clad enclosure made from 316 stainless steel, is being put to the test in the most severe climatic conditions. It is self-contained and can be checked, during maintenance, by a tester specifically developed for this lightning conductor. The Vega meets the European standards currently in force."
The company Helita invented the first lightning conductor with a high-voltage pulsed spark-over device: the Pulsar. This device also reduces the time needed for the formation and propagation of the ascending discharge. The Pulsar emits a signal with a specified and controlled amplitude and frequency. Arnaud Ballouhey, export sales manager at Helita, stresses that "the British Standards Institution, an independent body, validated the performance of the Pulsar, and its consistency over time, by giving it a certificate at the end of 1999".
To reinforce the protection of a building against lightning, the building can be covered by a meshed cage and provided with strike points on the roof, 50cm long and separated from one another by about 15m. These points are connected by a conductor, in the same way as for earths. On this principle, panels of large surface area fitted with numerous points, designed to emit charges through the Corona effect, can also act to divert lightning strikes.
The installation of lightning arresters makes it possible to protect electrical equipment, whether on high or low power networks. The lightning arrester routes the surges to earth before they can penetrate the installation. To ensure good protection, the lightning arrester has to act on surges occurring in common mode (between live or neutral and earth) and in differential mode (between live and neutral).
The choice of lightning arrester depends on two main criteria: the maximum discharge current (Imax) and the protection level (Up). Imax corresponds to the rating of the lightning arrester selected according to the nature of the site to be protected and the frequency of lightning observed in the area. The greater the risk factor, the higher the rating of the arrester needs to be. Whatever the area concerned, in a rural or industrial environment, a rating of 65kA can be justified. The Up or residual voltage of the arrester must be suitable for the sensitivity of the equipment to be protected. The lower its value, the better is the level of protection. The design of lightning arresters allows them, in general, to withstand up to 20 lightning strikes at the rated intensity (and one at maximum intensity).
The company Franklin France offers a discharge counter. Marie Bakker, assistant general manager, explains that "this tool is a logger designed to detect and count the lightning strikes received by lightning protection equipment. The safety officer or installer can therefore carry out specific maintenance on the equipment". Franklin France was already well-known for its Saint Elmo lightning conductor with its piezoelectric ceramic arcing stimulator.
Lightning arresters are now installed systematically for the protection of facilities such as radio relay stations, pumping stations (remote reading), toll barriers, etc. However, Emmanuel Francôois, marketing manager of Soule Protections Surtensions, says that "the lightning arrester is still, in France, a niche market but it is going to expand under the influence of the emergence of electronics into everyday life. As users are becoming more and more aware of the risks of lightning and the importance of protecting against it, the lightning arrester will tomorrow be as common for surge protection as the earth-leakage circuit-breaker is today for protection against indirect contacts".
Soule has launched a range of arrester sockets and multiple sockets known as DomoFoudre. "This range constitutes a turnkey solution for users requiring better overall or local protection for their equipment (televisions, telephones/faxes, computers/Internet). They will be able to install a DomoFoudre package that consists of an arrester for the distribution board and terminal protection". A network of DomoFoudre installers has been set up for individuals to help them in the selection and installation of the arresters.
An extensive campaign highlighting the importance of electrical safety on farms in general, and protection against lightning in particular, has been conducted by Electricite de France, Promotelec (organisation for the promotion of electrical safety), France Telecom and Groupama. This insurance company decided to invest in prevention by giving help to farmers so that they can increase the reliability of their installations.
The farming sector has made large investments, particularly in buildings for battery farming. Automated equipment, particularly for the feeding of animals, is increasing, and information technology is becoming widespread. As the smallest break in operation can have serious consequences (death of animals), the installation of lightning arresters ensures continuation of operation and therefore profitability.
For more information please contact Rob Williams at the FTPB. Tel: +44 (0) 20 7235 5330.