Lightning Protection Installation
(The pictures show a sampling of our installations.)
Protection from lightning
A properly installed lightning protection system protects buildings and lives by channeling lightning strike energy in a safe and controlled manner to the earth termination network. Lightning protection system (LPS) has four parts:
- Air terminals (lightning rods), also called lightning arresters, to intercept lightning
- Down conductors to carry the discharge current
- Equipotential bonding to prevent arc over to metallic objects near a down conductor
- Earthing system to dissipate the current away from the protected structure
A Rodhini LPS is the same system and the same components used in the USA.
Air terminals channel lightning strike current on to down conductors. There are two aspects to air terminals: (1) what kind they are and (2) where they are placed on a structure so that they will collectively protect the entire structure.
There are two kinds of air terminals used across the world:
- Conventional, which is a simple highly conductive rod – made of copper or aluminum. It is called Franklin rod.
- Non-conventional air terminals
Rodhini uses air terminals that are Franklin rods but with a slightly blunt tip as advocated by scientific research published in 2000, in the Journal of Geophysical Research, as having a greater chance of catching lightning strikes; these are now being increasingly used in the USA, Canada and China.
Non-conventional Air Terminals
The non-conventional are of two kinds – early streamer emission (ESE) air terminals and charge transfer systems (CTS). ESE emits a charge stream early – hence the name – when quiescent charge conditions are detected in the cloud above. In this manner it is claimed that such a terminal can preferentially connect with a charge streamer – called a leader – coming down from the cloud and thus protect a large area of the structure. International Standard IEC 62305 has not yet approved this due to not having validation based on the physics. However, many of the tallest buildings in the world have ESE terminals. These terminals are said to produce charges of tens of KV at their tips and produce leaders in the presence of leaders from the clouds. Assuming this to be true, it is difficult for cheaper installations to achieve this. Moreover, the battery charge needs to be maintained with solar attachment or otherwise.
It is clear that where only one Franklin rod is necessary on a structure, the more expensive non-conventional terminal is not needed. In any case,
CTS air terminals look like a crown of thick needles atop a mast. Proponents of CTS air terminals claim that ‘corona’ current emitted from their arrays of sharp points can help to neutralize some of the charge in the cloud above and thus prevent a strike. But field studies have not corroborated the claims. IE 62305 has not recommended CTS air terminals.
Placement of Air Terminals
Having the right type of air terminal is not sufficient. They must have the right height and be placed on the right locations on the structure so as to protect every portion of the structure. RODHINI uses the well-known scientific method called the Rolling Sphere Method to compute the location and heights of the terminals. This is the same method used in NASA’s new strung-wire system – which is the same as a system with many Franklin rods – to protect launch pads .
Down conductors pass on the strike current to the Earth Electrode System. They must have low resistance and low self-inductance at the frequency of the lightning current. They can touch the wall or metal parts so that the building and the conductor will be at the same potential and no harm will be done to the wall or other materials in contact with it. Equipotential Bonding. High voltage current passing through the down conductor of an LPS can create large electric potentials as compared to objects adjacent to it. This disparity can cause side jumps of charge, popularly known as ‘side flashes.’ So all metal bodies within 6 feet of the down conductor are connected using bonding jumpers to the down conductor. The earthing for house wiring is to be connected to the earthing of LPS. Likewise the live electric wires are bonded to the LPS earth. It is perfectly realized by using a Surge Protector – see more on this elsewhere in this brochure.
All-copper System: Rodhini uses round conductors that are either sold or woven. 20mmx3mm copper strip is also used. Rodhini manfactures stranded CU conductor (see the stranded conductor next to the solid round conductor in the picture). Inquiries are welcome.
Aluminum-copper System: Copper and aluminum are the metals to be used in lightning protection. Rodhini manufactures the aluminum components. Coupled with the copper underground, the total cost of the copper-aluminum LPS is about two-thirds of the standard all-copper system for tall structures like church spires. For buildings like houses, there is no cost-saving using aluminum as the labor cost is more for copper-aluminum LPS than for all-copper system. Rodhini is a pioneer in India in installing aluminum-copper LPS. Rodhini manufactures AL stranded conductor for wholesale. Inquiries are welcome.
This connects to the down conductor. Proper earthing is a must for the safe dispersal of the large amount of energy generated in a lightning-strike. Rodhini uses guidelines in IEC 62305 for earthing in different soil conditions. Accordingly, the system might be a single earth rod or multiple rods, earthing plates, meshes, earthing trench, or a combination of these to which the down conductor is connected.
The LPS installation and its components follow the guidelines of the lightning protection standard, IEC 62305.
Lightning Protection – a specialty discipline
IEC 62305 prescribes how to work with lightning to improve safety. LPS is not a do-it-yourself project. LPS should be installed by trained, experienced lightning protection specialists – the training of electricians does not include lightning protection system – in accordance with the national standard.