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Meeting the challenge -- Lightning protection

As wind turbines grow bigger, their vulnerability to lightning strikes increases, particularly in storm-prone areas like Japan. The costs of replacing a blade can exceed $100,000. American company Lightning Eliminators & Consultants Inc (LEC) of Boulder, Colorado, claim to have an effective solution. Plasma generators, says the company, are more effective than other means in intercepting and directing lightning safely.

LEC estimates that in one season, blades on at least 55 machines at a wind farm in Honshu, Japan, were destroyed by lightning at a cost in excess of $5.5 million. Instances of severe mechanical or fire damage to complete turbines have been seen.

Wind turbines are among the most challenging machines to protect from lightning because their most sensitive part is not only the most likely target but also the least likely to survive a strike. Since wind turbine blades are not electrical conductors, suppliers try to correct this by inserting conductive wire inside them to dissipate stray electrical energy. Blade failure occurs when the energy dissipated by inserted wire is not enough to handle lightning strikes and their aftermath. LEC, with global experience of lightning protection systems, has focused its studies on the science of strike collection. As a result, it has developed a patented collection system process known as the Ion Plasma Generator (IPG).

In a typical electrical storm, clouds emit a negatively-charged downward "leader" searching for an attractive, positively-charged, upward streamer or "counter leader" from the ground, to trigger a lightning strike and balance the electrical charge. Since lightning termination requires a rising conductive path from earth to close the circuit, an effective strike collector must generate the most "attractive" path in a competitive situation. Analytical, test and operational data prove the IPG successfully competes with other forms of streamer generated elsewhere, says LEC. The IPG directs the corona plasma upward to capture direct lightning strikes, influencing the lightning leader path in the last few microseconds of its trip to earth. The dense plasma presents a far more attractive force than wind turbine blades or any other form of streamer.

Two notable successes quoted by the company involve wind turbines that extend 72.5 metres into the air in the most lightning vulnerable areas of Japan, where peak lightning currents have been recorded up to 200,000 amperes. LEC installed IPG lightning protection systems on two wind turbine sites within a group of 15 in the area. At last report, all 13 unprotected wind turbine groups were struck by lightning, with at least one turbine blade destroyed in each group. To date, the two IPG-protected sites continue to function with no lightning related losses.

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