Lightning is a destructive natural discharge phenomenon with extremely high voltage and current, posing severe threats to buildings, power systems, equipment and personal safety. The core of the lightning protection industry is to guide, shunt and suppress lightning energy through scientific technologies to reduce disaster losses. This article sorts out the basic cognition of lightning protection, helping you quickly grasp the core principles and system composition.

1. Formation and Hazards of Lightning

Lightning is essentially an electrostatic discharge between clouds or between clouds and the ground. During atmospheric movement, collision and friction of particles in clouds cause charge separation (positive at the top, negative at the bottom). When the electric field strength exceeds the insulation limit of air, discharge occurs to form lightning, accompanied by thunder (generated by the instantaneous expansion of air).

There are three main types of lightning: ① Inter-cloud lightning, which has little impact on the ground; ② Cloud-to-ground lightning, which directly strikes the ground with the strongest destructiveness and is the core of protection; ③ Induced lightning, which generates overvoltage through electromagnetic or electrostatic induction and spreads along lines to damage electronic equipment.

Lightning hazards are divided into direct and indirect types: Direct hazards (direct lightning strike) cause building burning, fire, equipment damage and casualties through electrical, thermal and mechanical effects. Indirect hazards (induced lightning/lightning wave intrusion) are the most common, where strong electromagnetic fields induce overvoltage to damage electronic equipment, and potential differences formed by lightning striking the ground cause step voltage or contact voltage electric shocks.

2. Core Principles of Lightning Protection

The core idea of lightning protection is "scientific guidance" and "effective suppression" rather than preventing lightning. It can be summarized into six key principles:

1. Interception: Use lightning rods, air terminals and other lightning receptors to attract lightning first, avoiding protected objects from being struck.

2. Drainage: Down conductors safely guide the lightning current from lightning receptors to the grounding device.

3. Current Dissipation: The grounding device uniformly releases lightning current into the ground to reduce the potential gradient.

4. Equipotential Bonding: Connect protected objects with the grounding device to form an equipotential body, avoiding equipment damage or electric shock caused by potential differences.

5. Shielding: Metal shielding layers block electromagnetic pulses and reduce the impact of induced overvoltage.

6. Suppression: Surge Protective Devices (SPD) suppress overvoltage and limit it within a safe range.

3. Core Composition of Lightning Protection System

A complete lightning protection system consists of external and internal parts, which are indispensable:

3.1 External Lightning Protection System: The First Line of Defense Against Direct Lightning

It is mainly aimed at direct lightning strike protection, with core components including:

• Lightning Receptor: Front-end interceptor, common types include lightning rod (suitable for isolated buildings), air terminal/lightning protection net (suitable for large-area roofs) and lightning conductor (suitable for power lines, bridges, etc.).

• Down Conductor: Connect lightning receptors and grounding devices, requiring large cross-section conductors (copper ≥16mm², steel ≥25mm²) with short and straight laying. Generally, 2-4 down conductors are installed evenly around the building.

• Grounding Device: Including grounding electrodes and grounding wires, common types are vertical grounding electrodes, horizontal grounding electrodes or combined grounding grids. The core requirement is grounding resistance ≤10Ω (adjusted according to scenarios) to ensure rapid current dissipation into the ground.

3.2 Internal Lightning Protection System: The Second Line of Defense Against Induced Lightning

It is mainly aimed at induced lightning and lightning wave intrusion, protecting internal electronic equipment and power systems. Core components include equipotential bonding system, shielding and wiring, and SPD.

4. Lightning Protection Level and Protection Zone (LPZ) Classification

According to GB 50057 "Code for Design of Lightning Protection of Buildings", buildings are divided into three lightning protection levels: Class I (important buildings with severe lightning damage consequences), Class II (relatively important buildings with serious damage consequences) and Class III (other buildings needing lightning protection).

Lightning Protection Zones (LPZ) are divided by the intensity of lightning electromagnetic pulses, weakening from outside to inside: LPZ 0A (fully exposed to direct lightning and electromagnetic pulses), LPZ 0B (no direct lightning but exposed to strong electromagnetic pulses), LPZ 1 (electromagnetic pulses greatly attenuated after shielding) and LPZ 2 (further attenuated after multiple shielding).

5. Key Lightning Protection Standards

The lightning protection industry is highly standardized, with three main global standard systems: ① International standards: IEC 62305 series as the global reference benchmark; ② Domestic standards: Core standards include GB 50057-2010 (building lightning protection) and GB 50343-2012 (electronic information system lightning protection); ③ Regional/foreign standards: Such as EU EN 62305 (CE certification), US NFPA 780 (UL certification) and Japan JIS C series (special environment protection).