Lightning is a dangerous natural event that can cause a lot of damage to electrical infrastructure and even kill people. Lightning protection devices (LPDs) are put into buildings and other structures to disarm this force of nature — lightning rods, surge protectors, and grounding systems that redirect the electrical charge from a lightning strike away from the building or structure. Proper installation and maintenance of these devices are crucial to ensuring their effectiveness in preventing damage from lightning strikes.
Professionals who are qualified and adhere to industry standards and guidelines should install lightning protection systems. There are a number of different categories of lightning protection equipment, including: signal lightning arresters, ground protectors, lightning protection test equipment, LPDs for monitoring and controlling systems, and power supply LPDs and sockets. For these systems to keep working, they also need to be checked and maintained on a regular basis.
How does a lightning protection device work?
An LPD provides a safe path for lightning to follow to the ground, rather than passing through and damaging a structure or its occupants. Usually, the device is a lightning rod or air terminal at the top of a building that is connected to a conductor that leads to a grounding system. When lightning strikes, the device picks up the electricity and sends it safely to the ground. The conductive materials can be copper or aluminum installed on the roof and sides of a building and hooked to a grounding system.
Lightning rods are an important safety feature for tall buildings and structures, as they provide a path of least resistance for lightning to follow. Without a lightning rod, lightning could strike the structure itself, causing significant damage and putting people's lives at risk. A direct strike can cause fires, explosions and structural damage that can be costly and dangerous.
Damage caused by lightning strikes
Physical harm from a lightning strike may be devastating. However, mains and data cables might be damaged by voltage spikes induced by a close strike. Voltage surges in mains or data/communications cables are commonly referred to as a "secondary effect" of lightning, and there are three known mechanisms by which these surges are created:
- Resistive coupling
- Inductive coupling
- Capacitive coupling
Resistive coupling
The ground voltage around a structure spikes dramatically when lightning strikes the ground there. When the ground voltage rises, it can be transmitted back into the building through earthed pipework and other electrical earthing systems, wreaking havoc on the electrical system as it goes. Another way for the currents to spread is through any data or telecommunications cables that connect the damaged building to another building.
Inductive coupling
An enormous electromagnetic pulse of energy is produced when lightning strikes a lightning conductor that is part of a building's structural protection system, and this energy can be taken up by surrounding cables as a damaging voltage surge.
Capacitive coupling
High-voltage electrical lines that run along the ground are less likely to be struck by lightning than those that run overhead. Large portions of the lightning's energy will flow into the distribution system before being dissipated by inbuilt high voltage surge prevention devices. And because of its high frequency, it will capacitively couple through transformers into the electrical systems of individual buildings, wreaking havoc on whatever electronic equipment it supplies.
Difference between surge protection and lightning protection devices
Surge protection devices (SPD) are usually used to protect against smaller, more frequent surges caused by things like power outages or switching electrical loads, while LPDs are made to protect against the much larger and more damaging surges caused by lightning strikes. Also, LPDs often have grounding systems that send lightning energy away from the equipment they are protecting.
SPDs protect sensitive electrical and electronic equipment from damage caused by voltage and current spikes by detecting them and sending them away from the equipment. When there is a voltage surge, the SPD lets the extra voltage and current flow away from the equipment in a safe way. Most SPDs protect against surges with metal oxide varistors or gas discharge tubes. When working normally, these parts are made to have a very high resistance. However, when a voltage surge happens, they quickly become conductive, sending the extra voltage and current away from the equipment. Some SPDs also have filters to cut down on electromagnetic interference (EMI) and radio frequency interference (RFI), which can stop sensitive equipment from working or damage it. These filters work by blocking unwanted frequencies and allowing only the desired frequencies to pass through.
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Conclusion
People, electronics and electrical infrastructure are all vulnerable to lightning's lethal strikes. Lightning may cause significant damage to buildings and other structures; hence lightning protection systems are installed. Lightning rods, surge protectors and grounding systems are all examples of equipment that may divert the lightning's electrical energy away from a building. The effectiveness of these devices in warding off lightning strikes relies on them having been installed and maintained correctly.
