Users of electronic equipment and communication and information technology systems must keep their equipment in operation even if lightning strikes could cause short-term voltage spikes on the power supply and data lines.
There are several reasons for this:
- The electronic components used make these systems more susceptible to faults.
- Costly service interruptions are not acceptable.
- Data transmission networks extend over long distances and areas and are subject to more interference.
Lightning strikes, the subject of research since the first investigations by Benjamin Franklin in 1749, have become a growing threat to our electronic-dependent society.
Origin of lightning
Lightning occurs between two oppositely charged zones in the atmosphere, typically between two thunderclouds or between a cloud and the ground. It can travel over several kilometres in successive jumps to the ground, with a guide flash first causing a highly ionised lightning channel. Only when this reaches the ground does the actual flash or main flash occur. Then a current of several tens of thousands of amperes flows through the ionised channel from the ground to the cloud or vice versa.
At the time of discharge, a pulse current flows with a peak value between 1,000 and 200,000 amperes and a rise time of a few microseconds. The direct effects lead to damage to structural installations through mechanical damage or even a fire. The best protection is still provided by classic lightning conductors or lightning protection systems, which are designed to "capture" the leakage current and feed it to a specific point.
The direct effects of a lightning strike in structural installations affect their electrical and electronic systems in particular. High lightning currents lead to high potential rises and high voltage differences that can easily damage electrical equipment.