- 1 April 2020
- Posted by: Forend Forend
- Category: Lightning
The principle consists of creating one or more preferred impact points for a lightning strike using low impedance conductor elements. These then conduct and dissipate the lightning current into the ground. This coherent system enables the lightning to be captured and dissipated whilst providing protection to the structure.
There are four types of lightning conductors for protecting structures against lightning:
- Early Streamer Emission (E.S.E) Lightning Rod / E.S.E. Air Terminal
- Simple Rod/ Air Terminal
- Mesh Rod / Meshed Cage
- Catenary Wire Lightning Conductor
E.S.E Lightning Rods
In E.S.E Lightning Rod system, protection is enabled by means of an electrostatic lightning rod, the tip of which is refined and sharpened in both lightning rod systems, and lightning rods are placed on the highest spot of the construction to be protected.
E.S.E. Lightning rods are connected with the ground along the shortest route. The protection area they provide varies depending on the location of the installation and height of such location compared to the surrounding constructions. E.S.E. lightning rods suitable for ion devices also follow the same rules, however warning distance is further improved (about 1.5-3 times), because arc delay is reduced. Their advantage is to increase in efficiency, especially in the case of low-density lightning strikes, and to decrease in the lengths of lightning rods for some situations with very hard applicability.
Simple Rod / Air Terminal
Known as Franklin rod or air terminal systems, this method is a lightning protection method consisting of a basic metal tip, down conductor, and grounding sections. A metallic air terminal is placed on top of the construction to be protected, and ground connection is established. It provides a protection cone thanks to the α apex angle. In this method, an area specified with a fixed protection angle can be protected.
Places Where the Air Terminal Method Can Be Applied:
– Tower type constructions with small floors
– Mosque minarets, light houses, guard boxes, etc.
– Special spot protection in constructions with Faraday cages
– Chimney breasts, devices on flat roofs especially, elevator towers
Faraday (Cage) System
This is performed by combining the conductors that are placed at suitable distances from a cage on top of the building depending on the protection level, and providing connection with the ground. This provides a protection angle thanks to the rolling sphere method. Air terminals called strike points (0.50-2m) are mounted on each important point (chimney, roof bodywork, etc.) around the roof.
The building to be protected with the Faraday Cage method will be covered so that there is a continuous and uninterrupted conductor route from the top points of the building, including secondary parts to the ground. This cage has many attractors formed by conductors completed by horizontal connections and is connected to a grounding system. All metal extensions on the roof that is connected to the grounding system on purpose or incidentally must be connected to the air terminal system, and consist a part of the system. If the height of some parts of the construction varies significantly, the lower air terminal or air terminal system must be connected to the down conductors of high parts in addition to its own down conductor.
The protection area in the stretch wire method is defined with the combination of volume protected by the apparent rods on the wire. Stretch wire is bonded from the height that will protect the building between the poles erected on two or more sides. Poles must provide electrical continuity between the grounding of the stretch wire and poles, and the stretch wire must have a section (min 50mm2) that can bear the stretch wire lightning current. This method is not preferred on high buildings due to the difficulty of installing it and the unpleasant appearance it creates on the building.