When lightning strikes,everything is in danger including your equipment, appliances, structures and anything matter around the charged area. This calls for a system to be put in place not only to protect you and your loved ones but your structure, equipment and appliances as well. What is a lightning protection system and how does it protect you? How do you prevent this phenomena from hitting your property or your Electrical equipment?
What is a Lightning Protection System?
This is a passive means of preventing property damage from the effects of a lightning strike. Lightning protection systems act like a Faraday Cage for buildings. Protecting the building and its contents from external electric fields by migrating that energy around the cage instead of through its contents.The low resistant path offered by a lightning protection system is very important as high voltage currents from a lightning strike will always take a path of least resistance to ground. There are four main parts of a properly installed lightning protection system: copper air terminals, copper cable, copper clad ground rods, surge suppressors.
a) Copper Air Terminals
These are small, vertical protrusions designed to act as the 'terminal' for a lightning discharge. The rods can be found in different shapes, sizes and designs. Most are topped with a tall, pointed needle or a smooth, polished sphere.They are strategically sited on a structure to increase the chances of intercepting a lightning strike before it hits the property being protected. The highly conductive lightning rods of a lightning protection system are normally made of copper or aluminium and are designed to emit positive streamers into the air instead of the structure they are protecting. These positive streamers from the rods intercept the negative leaders of a lightning strike drawing the high voltage currents safely into the lightning protection system and away from the building’s structure.
b) Down conductors/Conductor cables
These are heavy cables or copper tapes that carry lightning current from the air termination rods to the ground. They should take the most direct route from the air termination rods to the earth termination system. Even though, down conductor positioning and distancing is often dictated by architectural constraints, there should be one down conductor for every 20m or part there of of the building perimeter at roof or ground level evenly spaced and distances apart of more than 20m avoided if possible. Reinforcement or structural metal work can be used as down conductors but only after the electrical continuity is ascertained from the air termination system to the earth termination systems
These are small, vertical protrusions designed to act as the 'terminal' for a lightning discharge. The rods can be found in different shapes, sizes and designs. Most are topped with a tall, pointed needle or a smooth, polished sphere.They are strategically sited on a structure to increase the chances of intercepting a lightning strike before it hits the property being protected. The highly conductive lightning rods of a lightning protection system are normally made of copper or aluminium and are designed to emit positive streamers into the air instead of the structure they are protecting. These positive streamers from the rods intercept the negative leaders of a lightning strike drawing the high voltage currents safely into the lightning protection system and away from the building’s structure.
b) Down conductors/Conductor cables
These are heavy cables or copper tapes that carry lightning current from the air termination rods to the ground. They should take the most direct route from the air termination rods to the earth termination system. Even though, down conductor positioning and distancing is often dictated by architectural constraints, there should be one down conductor for every 20m or part there of of the building perimeter at roof or ground level evenly spaced and distances apart of more than 20m avoided if possible. Reinforcement or structural metal work can be used as down conductors but only after the electrical continuity is ascertained from the air termination system to the earth termination systems
(c) Earth Termination Systems/Earth rods
Long, thick, heavy rods buried deep into the earth around a protected structure. The conductor cables are connected to these rods to complete a safe path for a lightning discharge around a structure. They are vital as they disperse lightning current safely and effectively into the ground. Each down conductor must have a separate earth termination. Moreover provision should be made in each down conductor, for disconnection from the earth for testing purposes.This is achieved with a test clamp.Several types of earth electrode are permissible, but by far the most commonly used are deep driven earth rods. The combined earth rod length of a system should be no less than 9m whilst each individual earth rod should be no less than 1.5m in length.If deep driving of earth rods cannot be achieved, a matrix arrangement of rods coupled to one another by conductors can be used spaced at a distance at least equal to their driven depth. If earth rods cannot be driven in a parallel line a "Crows Foot" configuration can be used, ensuring that the spacing/depth ratio is still maintained.
(d) Bonding After fitting your lightning protection system in place.
It is standard requirement that the system to be bonded to the building or structure grounding electrode system. This bonding connection is designed to minimize the difference of potential between the lightning protection system and the electrical system, which should reduce arcing/side flashing between metal parts within the building. All metal work, including water pipes, gas pipes, handrails, air conditioning units, metal cladding, metal roofs etc, in the vicinity of the lightning Protection System must be bonded to it, to avoid the danger of side flashing. For the same reason, the LPS earth should be bonded to the main electrical earth, as well as any other earthing system present in the structure.
(e) Surge arrestors
This is a device that protects your equipment from over voltage transients caused by Lightning. Their installations should be well co-ordinated with the LPS ensure it offers the necessary protection to your equipment as well ensure continuity of its operation.
Do you need a Lightning Protection System? You should contact a qualified personnel to ascertain whether your structure actually needs a LPS after which he should go a head and design a system that suits your need and your structure.
