What is lightning?
Lightning is a spectacular and dangerous natural phenomenon.
You naturally know what a thunderstorm is. Lightning illuminates the sky, and it roars with enormous crashes and booms. You also know that thunderstorms are dangerous. Damage can occur, for example fires, and lightning can kill animals and people.
To be able to protect against lightning, we must understand how thunderstorms work.
How does lightning occur?
Lightning is an electrical spark between two poles with different polarity, positive and negative, like a battery. If the voltage difference is high enough and there is sufficient energy behind it, the lightning will strike with destructive force.
What you see
The air is never still. Heat causes the air to rise, creating friction between water droplets and other particles in the air. If the concentration of water and particles is high enough, we see this as clouds. A thundercloud is large and dark because it contains large amounts of water and other particles moving around among each other. This creates static electricity, which can eventually be released as large sparks—either within the cloud, between two clouds, or between the cloud and the ground.
The lightning itself is only a few centimeters thick, but it is extremely hot—around 30,000 degrees. This enormous heat causes the particles in the air to become white-hot, which is what we see as a very bright flash of lightning.
A lightning strike typically lasts about a quarter of a second, but is perceived as lasting longer because the air becomes white-hot and takes some time to cool down again.
What you hear
It is the intense heating of the air around the lightning that we hear as thunder. The air is heated so rapidly and so violently that it expands explosively, producing a loud bang that we call thunder.
Sound travels at roughly one third the speed of light. This means that we hear the thunder with a delay depending on the distance. If we see a lightning strike and only hear the sound after about three seconds, we can calculate the distance to be approximately 1 kilometer.
What you don’t see
Most lightning discharges occur between clouds, but some also strike the ground.
Can we predict where lightning will strike? No, not precisely. But by understanding the conditions, we can help control the process to avoid damage. This is the fundamental principle of lightning protection.
Lightning will always seek the easiest and most efficient path to the ground—that is, the path with the least resistance.
Lightning does not travel in a straight line through the air, but is characterized by a zigzag path. This path is known as the lightning channel. The composition of particles and air humidity determines how this path is formed.
In practice, ionization of the air occurs. This can sometimes be seen as a faint purple glow (plasma) when air molecules are split into positive and negative ions. Ionization allows electrons to move more freely, and can therefore be perceived as a conductor. This is referred to as a lightning leader.
The most efficient path is not necessarily toward the highest or most prominent point on the earth’s surface.
Just as the electric field beneath the cloud creates ionization—and thus a lightning leader—the same occurs due to the electric field at the ground. So-called streamers are formed, reaching upward toward the thundercloud.
However, it is the leader from the cloud that determines where the strike will occur. When the leader and the streamer meet, the connection is completed and the lightning is discharged.
Lightning conductor
Lightning protection consists of a lightning conductor that is installed at a high point and connected to an effective earthing system.
The purpose is not to attract lightning to the building, but to ensure that if lightning does strike the building, the lightning conductor provides the most efficient path to the ground. In this way, the building is protected against damage caused by the extreme current and heat.
The lightning conductor must be positioned above the building, as this is where the ionized lightning channel will connect. This also means that the extreme heating of the air ends at this point, thereby preventing fire.
Would you like to know more?
If you would like to know more or have any further questions, please feel free to contact us. We are ready to help.
