How to Design Lightning Protection to a Budget
Lightning protection systems are the outcome of the innovation pioneered by Benjamin Franklin: the lightning rod. Lightning protection systems are used today on many buildings such as, homes, communication towers, high rise buildings, and mobile structures.
We will look into why lightning protection is essential and what the systems are able to do, that include:
– Components of a lightning protection system
– Lightning protection systems
– What they do and do not do
– How a lightning protection system works
– Lightning and Surge Protectors / UPS Devices
– Lightning dissipation / elimination myths
Components of a lightning protection system
Lightning rods or ‘air terminals’ are only a tiny part of a complete lightning protection system. Actually, the rods may play the minor role in a system installation. A lightning protection system is collected of three main components:
1. Rods or ‘Air Terminals’ – The small, vertical rods are made to behave as the ‘terminal’ for a lightning discharge. Rods are designed in different shapes, sizes from long poles to Erico’s Dynaspheres.
2. Conductor Cables – Cables carry the lightning from the rods to the ground. Interconnected cables are set along the tops and around the edges of roofs, then down the building to the ground rod(s) that form the earthing part of the system.
3. Ground Rods – Long, thick, heavy rods are buried down into the ground around a protected structure. The conductor cables are connected to these rods to finish a safe path for a lightning discharge around a structure.
The conductor cables and ground rods are the most consequential components of a lightning protection system, completing the main objective of diverting lightning current safely past a structure.
What does Lightning protection systems do?
The purpose of a lightning protection is to improve and ensure the safety to a building, equipment and its occupants if lightning happens to strike.
A well-designed system will:
- Attract lightning to a planned point (Lightning rod)
- Dissipate or prevent lightning by ‘draining’ a storm of its charge
- Offer surge protection for sensitive electronics
- Offer fire and structural damage protection by preventing a hot, explosive lightning channel from passing through building materials
Without a designed path to reach ground, a lightning strike is able to utilize any conductor available inside any type of building. This may include the phone, cable, or other electrical lines, the water and gas pipes, or if a steel-framed building, the structure itself.
It is normal that lightning follows one of these paths to the ground, sometimes jumping through the air via a side flash to reach a better-grounded conductor. Therefore, lightning presents several hazards to any type of building:
- Fire can start anywhere the exposed lightning channel contacts, penetrates or comes near flammable material (wood, paper, gas pipes, etc) in a building. When lightning follows electrical conduits, it will often overheat or even vaporize the wires, creating a fire hazard anywhere along affected circuits.
- Side flashes – Side flashes jump across rooms, and can also ignite materials.
- Damage to building materials – The explosive shock wave that comes from a lightning discharge is able to blow out sections of walls, fragment concrete, plaster and make nearby glass shatter.
- Damage to appliances – Computers, mechanical, electrical equipment, in general anything plugged are vulnerable to be damaged beyond repair.
Adding a protection system does not prevent a strike, but gives it a better, safer path to ground. The air terminals, cables and ground rods work together to hold the immense currents away from the structure, avoiding fire and most appliance damage:
Lightning and Surge Protectors / UPS Devices
Surge protectors and UPS units are not decent lightning protection devices. These appliances offer protection from voltage spikes from everyday power surges and distant lightning strikes.
A normal surge protector cannot have any effect on the violent burst of current from a very close or direct lightning strike. Direct lightning current is simply too big to protect.
Even ‘disconnects’, or devices that physically switch off power to a device by activating a set of contacts, will not guarantee protection. A small air gap will not stop a lightning bolt that has already jumped across miles of air.
For any lightning protection system to provide protection, it must divert the lightning current from a direct strike.
Ohm’s Law states that for a set of resistances connected in parallel, the current will be distributed across ALL resistances, at levels inversely proportional to the different values of resistance.
A structure or building is nothing more than a set of resistors ‘connected’ in parallel- the electrical wiring, plumbing, phone lines, steel framework, etc. (Even though plumbing and electrical wiring, for instance, may not be physically connected, lightning will use side flashes across air gaps to effectively connect them). In a direct lightning strike, the current will not follow only one path- it will distribute itself across all paths to ground depending on each path’s resistance.
Lightning current often peaks at 100,000 or more Amperes. With that in mind, consider if you have a lightning protection system installed, and your building is hit directly by lightning. If the protection system takes even 99.9% of the current, then your electrical wiring may take the remaining 0.1%. 0.1% of 100,000 Amperes is a 100 Amp surge through your lines- which may be enough to take out your computer or other equipment.
It is common for ‘side flashes’ to occur, where all or a part of the lightning will jump across an entire room to reach ground- such as from the electrical wiring system to well-grounded water pipes.
All this means, you should use a surge protector or a full-fledged lightning rod system.
Lightning protection facts
- An effective lightning protection systems can intercept a lightning strike.
- Protection systems prevent lightning damage and electrical discharge to earth
- Lightning protection systems (including placement of rods, cables, and groundings) are custom-designed for individual structures and require complex engineering to function properly. They should only be installed by qualified contractors using quality products such as the Erico range from West Australian Power Protection (WAPP).
For more information please contact us on Ph: (08) 9451 2199