Question

Explain the working of the lightning rods.

Answer 1

1. A lightning rod is an external terminal installed in a building or structure that aims to attract the lightning to have a controlled point of impact and prevent it from striking an unwanted area or people.
2. There are several types of lightning rods with different characteristics. But they are composed of metallic materials and their morphology is based on one or more protruding points where the discharge impacts.
3. The entire installation is called Lightning Protection System, it is mainly composed of:

1. Capture systems (lightning rods)

2. Down conductor

3. Grounding system

4. Surge arrestors

Working of lightning rods:

1. We indicate that it’s an air terminal that gives external protection to a building or structure from direct lightning strike impacts.
2. In that way, the lightning rod needs to be installed always over the highest point of the building or structure we need to protect, it will be in charge of capturing and conducting safely the lightning discharge to the ground.
3. In order to capture this discharge, the lightning rod has a tip and a metallic body, which are connected by a conducting network to a low impedance earthing system (less than $10\Omega$) where the lightning discharge dissipates.
4. In storm conditions, high voltage occurs between the cloud-earth system due to the large number of electrical charges that are present both at the base of the cloud and on the ground.
5. This high voltage is the trigger to start the leader descended from the beam, which will drill the dielectric air between the cloud and the ground.
6. The very high electric field $E(kV/m)$, that appears in that zone, produces a circulation of ascending electric charges through the body of the lightning conductor of the opposite sign initiating an ascending tracer, which will meet and recombine with the descendant leader, capturing it and unloading it to the ground.