T 1.3 Lightning

The occurrence of lightning during a thunderstorm is a major threat to a building and the IT facilities accommodated there. With a voltage of several hundred thousand volts, lightning strikes can achieve currents of up to 200,000 amperes. This enormous electrical energy is released and dies away within a period of 50-100 microseconds. A lightning strike of this order of magnitude originating from a distance of about 2 km will still cause voltage peaks that are capable of destroying sensitive electronic devices in the power lines of the building. The closer the lightning strike is, the greater the indirect damage.

If a building is directly hit by lightning, damage will be caused by the dynamic energy of the lightning strike. This may include physical damage to the structure (roof and façade), damage caused by resultant fire, or overvoltage damage to electric devices.

The German Meteorological Service provides information on the risk of lightning in the various regions.

Examples

• At a major German airport there was a lightning strike very close to the air traffic control tower. Despite the external lightning protection system (lightning conductor) that had been installed, the automatic fire extinguishing system in the IT area was triggered and as a result all airport operations were paralysed for two hours.

• As well as direct damage, lightning often has more far-reaching consequences. Reports such as that reporting a lightning strike on a high-voltage line in the vicinity of Darmstadt in April 1999 that resulted in a short-term power failure affecting around 80,000 persons are quite common.