Helplessly exposed to nature? How lightning storms can be measured

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Courtesy of G. Lufft Mess- und Regeltechnik GmbH

Each day, there occur about 1,000 thunderstorms with 4-10 million lightning bolts worldwide. In average, 700 people per year are hit by such light discharges, of which 75% of the hits result in long-term damages. Between three and seven cases end fatal. The risk is particularly high in the open field and is fortunately decreasing. The reason for this is that we stay more often inside in cars and buildings where almost all areas are protected by lightning arresters than outside.

How do thunderstorms and lightnings develop at all?

Clouds are formed when moist air rises, which was warmed up before by the sun in the lower air layer. There, the air cools down again and forms tiny droplets.

If the water vapor troplets in the air rub present ice crystals at high altitudes, thunderclouds (cumulonimbus) are formed, because positively and negatively charged raindrops separate from each other. Through this, the cloud gets loaded electrostatically. At some point, the voltage discharges in the form of a lightning bolt and the heavy ice crystals falling to the earth as hail or rain.

Solar panels, wind turbines and power lines: helplessly exposed?

For power lines, wind turbines and photovoltaic plants, lightning strikes have serious consequences: They are exposed to them almost defenseless. In case of lightning flashes causing surge or even fire damages, there’s usually a lack of evidence for their origin – a nightmare for the plant operators who depend on their insurance and face high economic losses.

After all, nearly 20% of photovoltaic systems’ damages are caused by lightning bolts. To avoid a strike, they can be protected by so-called surge protective devices. The conditions of such devices are now standardizes by the European Norm EN50539-11:2013: “Requirements and tests of surge protection devices for photovoltaic systems”. Basically, a lightning protection device should be installed when it comes to performances of 10kW and more.

The WS 800–UMB: lightning detection and weather information at once

In addition, a lightning sensor for detecting and counting the emitted electromagnetic waves of lightning bolts makes sense. Last October we introduced the WS800-UMB weather sensor featuring this function. Besides lightning, the all-in-one sensor measures relative humidity, air pressure, wind direction and speed, rainfall intensity and volume as well as the global radiation. Since large solar and wind turbine plants are already controlled by weather sensors, the WS800 thus fulfils many requirements at once and with a single cable connection. Also potential confounders are no problem: Extensive experimental setups with the lightning simulator both in the laboratory and afield showed, that the sensor is resistant against other electromagnetic radiations in the environment, such as those of high speed railways.

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