Lightning is a damaging natural electrical discharge phenomenon with extremely high voltage and current, which poses significant risks to buildings, power grids, electrical devices, and human safety. The primary goal of the lightning protection industry is to guide, divert, and suppress lightning energy using scientific and technological methods, thereby minimizing the losses caused by lightning disasters. This article collates the basic concepts of lightning protection, enabling readers to quickly understand its core fundamentals and system components.
1. The Formation and Hazards of Lightning
In essence, lightning is an electrostatic discharge process that occurs either between clouds or between clouds and the ground. During atmospheric circulation, particles within clouds collide and rub against each other, leading to charge separation—with positive charges accumulating at the top of the cloud and negative charges at the bottom. When the electric field intensity surpasses the insulating capacity of air, a discharge takes place, forming lightning, which is accompanied by thunder (produced by the sudden expansion of air).
There are three main categories of lightning: ① Inter-cloud lightning, which has minimal impact on the ground; ② Cloud-to-ground lightning, which strikes the earth directly and is the most destructive type, making it the primary target of lightning protection measures; ③ Induced lightning, which generates overvoltage through electromagnetic or electrostatic induction and propagates along power lines, resulting in damage to electronic equipment.
Lightning hazards can be categorized into direct and indirect types: Direct hazards (caused by direct lightning strikes) result in building fires, equipment destruction, and human casualties through electrical, thermal, and mechanical effects. Indirect hazards (caused by induced lightning or lightning wave intrusion) are the most common. Overvoltages induced by strong electromagnetic fields can damage electronic devices, and potential differences formed when lightning strikes the ground can lead to step voltage or contact voltage electric shocks.
2. Core Fundamentals of Lightning Protection
The core concept of lightning protection lies in "scientific diversion" and "effective suppression" rather than preventing lightning from occurring altogether. It can be summarized into six key principles:
1.Interception: Utilize lightning rods, air terminals, and other lightning receptors to attract lightning first, thus preventing protected objects from being struck.
2.Diversion: Down conductors safely channel the lightning current captured by lightning receptors to the grounding system.
3.Dissipation: The grounding system evenly releases the lightning current into the ground, reducing the potential gradient.
4.Equipotential Bonding: Connect protected objects to the grounding system to form an equipotential body, avoiding equipment damage or human electric shock caused by potential differences.
5.Shielding: Metal shielding layers block electromagnetic pulses, reducing the impact of induced overvoltages.
6.Suppression: Surge Protective Devices (SPDs) suppress overvoltages and limit them within a safe range.
3. Core Components of a Lightning Protection System
A complete lightning protection system consists of external and internal components, both of which are indispensable:
3.1 External Lightning Protection System: The First Line of Defense Against Direct Lightning Strikes
This system is primarily designed to protect against direct lightning strikes, with its core components including:
•Lightning Receptor: A front-end interception device available in various types, such as lightning rods (suitable for isolated buildings), air terminals/lightning protection nets (suitable for buildings with large roof areas), and lightning conductors (suitable for power lines, bridges, etc.).
•Down Conductor: Connects lightning receptors to the grounding system and requires conductors with a large cross-sectional area (copper ≥16mm², steel ≥25mm²) laid in a short and straight path. Typically, 2 to 4 down conductors are installed evenly around a building.
•Grounding System: Comprises grounding electrodes and grounding wires, with common types including vertical grounding electrodes, horizontal grounding electrodes, or combined grounding grids. The key requirement is a grounding resistance of ≤10Ω (adjustable according to specific scenarios) to ensure the rapid dissipation of lightning current into the ground.
3.2 Internal Lightning Protection System: The Second Line of Defense Against Induced Lightning
This system is mainly intended to protect against induced lightning and lightning wave intrusion, safeguarding the electronic equipment and power systems inside buildings. Its core components include an equipotential bonding system, a shielding and wiring system, and SPDs 
4. Lightning Protection Levels and Lightning Protection Zone (LPZ) Classification
In accordance with GB 50057 "Code for Design of Lightning Protection of Buildings", buildings are classified into three lightning protection levels: Class I (critical buildings with severe potential lightning damage consequences), Class II (important buildings with significant potential lightning damage consequences), and Class III (other buildings requiring lightning protection).
Lightning Protection Zones (LPZs) are divided based on the intensity of lightning electromagnetic pulses, which decreases from the outside to the inside: LPZ 0A (areas fully exposed to direct lightning and electromagnetic pulses), LPZ 0B (areas not exposed to direct lightning but exposed to strong electromagnetic pulses), LPZ 1 (areas where electromagnetic pulses are significantly attenuated by shielding), and LPZ 2 (areas where electromagnetic pulses are further attenuated by multiple layers of shielding).
5. Key Lightning Protection Standards
The lightning protection industry is highly standardized, with three major global standard systems: ① International standards: The IEC 62305 series serves as the global reference benchmark; ② Domestic standards: Core standards include GB 50057-2010 (for building lightning protection) and GB 50343-2012 (for lightning protection of building electronic information systems); ③ Regional/foreign standards: Examples include the EU's EN 62305 (requiring CE certification), the US's NFPA 780 (requiring UL certification), and Japan's JIS C series (focusing on protection in special environments).