Lightning discharge is observed in the form of a light from the cloud to the ground. However, it goes out after it has covered part of the path between the cloud and the ground. After a period of time that can be measured in microseconds, a second flux follows the path of the first flux and thus a pre-discharge occurs. This type of flux is also called “pilot discharge”. Because the cloud base charge is negative, the pilot discharges are extinguished before they reach ground. The tip of the pilot discharges is very close to the ground. However, the jumps are 30-40 meters long and independent of the soil surface.
As a result of the increase in the electric field intensity on the soil surface with the movement of the pilot flux, a discharge that we can call the “Ground discharge” in the opposite direction (from the ground up) and with a positive (+) value arises. This discharge continues until the pilot, which has begun to extinguish, reaches the discharge and its path to the charged cloud. (This is the reason why it is wondered whether the lightning discharge is air-to-ground or ground-to-air) At this stage, the second phase is now formed. The activation phase of the active lightning rod is in the second phase. By increasing the intensified electric field, they ensure that the main discharge is grounded on themselves, not from anywhere, in the next phase.
Now the ground discharge has reached the charged cloud. Other discharges from the cloud, which could not discharge its charge in the previous phases, now follow the ionized channel formed by this ground discharge and flow to the ground through this channel one after the other. Therefore, they flow to the ground over the active lightning rod, which has increased the electric field intensity in the second phase. This is why active lightning rods are called “Early Flow Alert (E.S.E)”.
It is the most classical method of lightning protection. The conductor rod, which is mounted on a high place, creates a 45 degree protection area towards the ground, with the apex. This cone extending down from its apex is called the “Franklin cone”. The protective field radius is equal to the height of the catch tip from the ground (h). It does not have lightning protection feature when used in buildings in large areas, and it has an effective protection area in structures with narrow base but high height such as minarets, chimneys, towers and lighthouses. It is a lightning protection method that is still used in thin and long structures, which are still mentioned today.
This system, named after its inventor, Michael Faraday, is used to protect buildings or buildings spread over a wide area from lightning. It is an advanced version of the Franklin bar system with an overall perspective. It is based on the principle of extending the conductors in width and length according to the desired protection efficiency on the roof of the building, mounting a catch point at each intersection, and grounding the conductors by extending them to the ground throughout the building. Lowering conductors are connected to the grounding conductor, which is formed at the ground level of the building and surrounds the building. Although the system is still in use, it is not widely used due to its inability to protect the exterior of the building from lightning and its high cost.
Active lightning rods are also known as lightning rods working with the early flow warning principle. They are also defined as E.S.E active lightning rod by taking the initials of the Early Streamer Emission English word group. The working principle of active lightning rods is based on increasing the electric field intensity according to the current air loads. Thus, it provides protection against negative or positive lightning types. This method, which has been developed recently in lightning protection, is rapidly becoming widespread. The working principle of these lightning rods is to catch the lightning before it merges with the earth and transfer the discharge to the ground safely. For this reason, the catching speed (Δt) becomes important in active lightning rods. Thanks to the electric field it creates in the air, the active lightning rods, which prepare a conductive path to the lightning and give it to the ground, do not cause unnecessary discharges because they do not ionize the air. Active lightning rods (ESE) get their energy from the change of electrostatic and electromagnetic field density in the air.
The most important features of active lightning rods are that they provide effective protection from lightning in the circular area where they are installed. Therefore, with a suitable project, both economical and effective lightning protection is made with active lightning rods. In active lightning rod systems, a single point landing from the lightning rod facility to the ground is sufficient. However, in very high buildings, it is necessary to lay the conductor on the outer surface of the building horizontally every 20 m, and this system is called “belting”. The grounding of the active lightning rod system, just like the faraday cage, must be extremely good. Usage areas of active lightning rods: Active lightning rods, which can be applied to all buildings, open areas easily and in various ways, are suitable for life such as schools, hospitals, factory buildings, base stations, fuel filling and sales stations, airports, stadiums, apartments, summer sites, mosques, churches and synagogues. It is used in all buildings and facilities in our area.
