No thunder weather despite lightning: special lightning protection concept prevents weather stations from falling victim to the weather

An entire network of weather stations is in use throughout Germany so that we know today what the weather will be like tomorrow. The sensors collect their data, especially on mountain peaks, despite wind, rain and snow. This becomes problematic during thunderstorms, because the sensors in this exposed position attract lightning – and they are much more common from a height of 1,000 meters. In order to protect the sensitive devices of his latest project on the Wendelstein, Germany’s leading equipment for weather stations, Thies Clima, therefore resorted to special lightning and surge protection. The Echterdinger Leutron GmbH concept is based on the bundling of security measures at a central point and has already proven itself in other locations prone to lightning.

“We heard during the planning stage that the Wendelstein often flashes,” says graduate engineer Stefan Helten from Thies Clima. The 1,838 meter high mountain in the Bavarian Alps protrudes far from the surrounding mountain range and is therefore the preferred destination for thunderstorms, which arise here from the collision of warm air from the south with cooler north winds. The ideal position for a weather station, which is why weather observations have been made on the Wendelstein since 1804 and the German Weather Service has had its own weather station on the summit since 1957. However, the location in the middle of the storm fronts is rather unfavorable for the highly sensitive measuring systems that are to collect data for a research institute at the newly built station.

In particular, the wind sensors installed at an exposed point, which measure the strength and direction of the wind, are very at risk from lightning strikes, reports Joachim Beinhorn, Development Manager at Thies Clima, from his experience. “But also the data logger with which the recorded values are recorded and the transmission technology can be damaged by the overvoltage of lightning discharges.” These defects can account for up to 40 percent of the total costs of a new system. In the event of direct impacts, there is also damage to the cabling, but a lightning strike in the area is also sufficient to severely disrupt the high-tech systems. At the weather station of Jörg Kachelmann’s (meteomedia) weather service on Belchen in the Black Forest, the discharges used to cause significant damage twice a year. Again and again, service employees had to climb to the summit in rain and wind to repair the devices.

Protective wall at the eye of the needle: All lines are bundled at a securing point

Since 2005 it has only been flashing on the Belchen without thunderstorms and destroyed electronics. At that time, Leutron GmbH from Leinfelden-Echterdingen installed a new type of lightning protection at the weather station. Normally, all components of the weather station would have to be individually shielded with protective devices, since the lightning protection zone concept that is common in buildings cannot be used. The Leutron engineers used a different principle instead. Sensors, transmission devices and network connections are combined to form a protective area, into which all lines enter at the same point. “This is where all of the lightning and surge protection elements are located and from here there is a single lead to the earth electrode,” explains Helmut Zitzmann, sales engineer at Leutron.

A Franklin rod, which is connected to the earthing system via a special arrester cable, also serves as external lightning protection. Due to its particularly wide cross section, this arrester cable can also handle very strong lightning currents. Added to this are its low electromagnetic coupling and high insulation capability, which also contribute to protection. The system was first tested at a weather station on the Belchen – and under difficult conditions, as it flashes twice as often on this summit as in the rest of Germany. The system’s lightning counter registered two severe impacts in the first four months. In 2007, the lightning information service from Siemens (BLIDS) recorded a total of 231 lightning strikes within three kilometers of the summit. The strongest discharge was 110 kiloamps. Nevertheless, there has been no damage to the measuring station since then, as certified engineer Beinhorn confirmed. “Now that the system works so well on the Belchen, we now always recommend our customers to use lightning protection based on this principle when it comes to a location that is at risk of lightning,” explains Helten. He therefore planned the special lightning protection when designing the newly built facility on the Wendelstein, so that the weather station itself did not become a victim of the weather.