What is Lightning?
Lightning is an electrical discharge in the atmosphere between clouds and the structures on the ground. It's basically a path for the current to flow to ground, and it happens in microseconds, with an enormous rise in heat, pressure, and energy at the strike point.
Lightning is the biggest threat for regions like Africa, South Asia, North America, Latin America and Australia
How Lightning OCCURS
Lightning clouds are usually vertically developed (cumulative) type and large enough to contain different charge groups at various heights. CumuloNimbus (Cb) clouds are the ones where lightning is most often observed. The bottom layer of this cloud is about 500 meters above the ground, and the top layer may rise to 8000 meters in the atmosphere. Cb clouds have different charge groups inside. The bottom layer is usually negatively(-) charged, where the top layer has mostly positive(+) charges.
As the storm grows, negative charges begin moving downward in the form of branches, and these are called “stepped leaders”. They move step by step to a height of 200 meters above the ground and stop. At that moment, positive charges called "upward streamers" are emitted from any object, building, or structure on the ground, and march towards the negatively charged branches in the sky.
One of the upward streamers meets the stepped leader, forming an ionized channel called a "Lightning Strike".
All current inside the cloud flows through this ionized path, following the structure body, and reaches the ground. During this electrical discharge, lightning current can directly damage structures and electronic equipment, and cause injuries and even deaths.
Lightning Damage on METAL TOWERS
Metal structures such as telecommunication towers, radio-tv towers, tower cranes, high-voltage power transmission towers, wind turbines, security camera poles, and weather station towers are primary targets of lightning strikes because they are made of conductive materials and they are usually the tallest structures in a location.
When lightning strikes the tower, the lightning current flows down through the tower's body and to the ground. During this flow, lightning current damages any equipment on the tower and in the nearby shelter. The electromagnetic field from the lightning current also affects the sensitive electronics on the tower body and inside the shelter. Site goes offline, equipment needs to be renewed, and maintenance costs arise.
A proper lightning protection solution is a must for these kinds of structures. In many parts of the world, metal towers are protected by traditional lightning arresters with down conductors attached. Lightning arresters attract lightning and divert the current to the conductor.
However, since the conductor is mounted directly on the tower body, current finds the tower surface a better path to the ground and prefers to flow through the tower body. This results in damage to the equipment on the tower and inside the shelter.
Traditional lightning arresters are not made for metal towers and cannot protect the site from lightning strikes.
Lightning must be kept AWAY from metal towers.
Lightning Arrester
