In any lightning protection installation, you often hear about lightning rods , surge arresters , and grounding . These three devices form an integrated, complementary, and inseparable system. It's not a matter of choosing one over another, but of understanding the precise role of each in order to build truly comprehensive lightning protection that complies with current standards.
This article explains why these three elements are complementary, what phenomena each covers, and how they fit together in an installation that complies with the IEC 62305 .
The lightning rod: protection against direct lightning strikes
The lightning rod —whether a simple rod (Franklin type) or an Early Streamer Emission (ESE) lightning rod —is to intercept direct lightning before it reaches the protected structure. By capturing the impact at a precise and controlled point, it channels the energy to the ground via feeder conductors, protecting structures and occupants.
This is a direct phenomenon : lightning physically strikes the building or its immediate surroundings. The lightning rod acts like an electrical umbrella, safely attracting and guiding the lightning arc. The protection radius of a lightning rod is calculated according to standard NF C 17-102 , taking into account, in particular, the ground lightning density Ng (number of ground strikes per km² per year) specific to each region of France, as well as the air lightning density Nsg.
Without a lightning rod, a direct lightning strike can cause considerable structural damage: fire, explosion, partial collapse. It is the first essential level of protection.
The Paraton@ir : a connected ESE for active and traceable protection
LPS France offers the Paraton@ir , an IoT-connected PDA that combines direct physical protection with real-time information transmission. Thanks to the Contact@ir , each impact is detected, time-stamped, and automatically transmitted—enabling data-driven maintenance and complete regulatory traceability.
The SPD surge arrester: protection against induced overvoltages
Even when lightning strikes hundreds of meters from a building, it can cause transient power surges in electrical networks, communication cables, or data circuits. These surges, known as indirect phenomena or lightning-induced surges , are invisible to the naked eye but extremely destructive to sensitive electronic equipment.
This is where the SPD (Surge Protective Device) comes in. Its role is to divert these overvoltages to ground before they reach sensitive equipment. In accordance with the IEC 62305-4 , surge protectors are classified into several types according to their positioning and absorption capacity:
- Type 1 : installed at the head of the main distribution board (TGBT), protects against lightning strikes hitting upstream or on the structure itself
- Type 2 : protects secondary distribution boards against residual overvoltages
- Type 3 : terminal protection as close as possible to sensitive equipment (IT, automation)
A surge protector does not protect against direct lightning strikes — that's the role of a lightning rod. It complements the protection by covering the indirect phenomenon , that is, the effects of lightning at a distance on the networks supplying the building.
Grounding: an essential condition for the system to function
Grounding is often misunderstood: it is not lightning protection per se, but it is an absolute requirement for its operation . Without a quality ground connection, neither the lightning rod nor the surge protector can fulfill its role effectively.
Its role is to ensure the discharge of lightning currents —whether from a direct strike captured by the lightning rod or from a surge diverted by the surge protector—to the ground, without a potential rise dangerous to people and equipment. Excessive ground resistance compromises the effectiveness of the entire system.
The IEC 62305-3 defines the requirements for the earthing system of a lightning protection system (LPS), including:
- The impulse resistance of the grounding electrode depends on the type of soil
- Safety distances between feeder conductors and metallic masses
- The interconnection of masses and the lightning Equipotential Spark Gap (LEB)
An effective grounding system is therefore the common foundation upon which lightning rods and surge protectors rely. It must be designed from the initial planning phase and checked periodically according to the installation's maintenance schedule.
Why are the three elements inseparable according to IEC 62305?
A common mistake is to install only a lightning rod, believing that lightning protection is complete. However, the IEC 62305 mandates a comprehensive approach that integrates:
- External protection ( lightning rod + supply conductors + grounding) against direct lightning strikes
- Internal protection ( SPD surge arresters, equipotential bonding, shielding) against indirect effects
- A common and efficient earth network connecting all these devices
A building equipped with a lightning rod but without surge protectors remains vulnerable to power surges on its electrical systems—which can destroy servers, industrial automation systems, or medical equipment in the event of a nearby strike. Conversely, surge protectors without lightning rods offer no protection against a direct strike to the structure.
Complementarity is therefore a physical and normative reality, not a commercial option.
Lightning Risk Analysis: A Mandatory Starting Point
Before any installation, the IEC 62305-2 requires a Lightning Risk Analysis (LRA) . This study allows for:
- Assess the risk related to local lightning strike density (Ng in impacts/km²/year according to Météorage data)
- Identify the structures and equipment that require priority protection
- Determine the required level of protection (NPF I to IV)
- Define the optimal combination: lightning rod type, surge arrester levels, target earth resistance
In France, the ground lightning strike density (Ng) varies from less than 1 strike/km²/year in Brittany to more than 4 in certain storm-prone areas of the Southwest. This data, combined with the characteristics of the structure and the nature of the activities (ICPE, tertiary, industrial), entirely determines the sizing of the protection system.
Maintenance and monitoring: keeping the system operational
A complete lightning protection system is only valuable if it is kept in working order. Periodic checks include:
- Visual and electrical inspection of the lightning rod (condition of the lightning rod head, continuity of the supply conductors)
- Earth resistance measurement (to be maintained according to the normative thresholds of IEC 62305-3)
- Checking the status of SPD surge arresters (triggering indicator, continuity, Uc measurement)
- Systematic verification after every lightning strike reported on the site
LPS France 's Contact@ir system allows this monitoring to be digitized : each connected component automatically sends its data to the LPS Manager , which generates alerts and compliance reports without systematic control tours.
Conclusion: Effective lightning protection is a comprehensive system
Lightning rods, surge protectors, and grounding are not three options to be chosen from. They are three complementary pillars of the same protection architecture, each covering a specific aspect of lightning risk:
- The lightning rod intercepts and channels direct lightning.
- The SPD surge protector diverts induced overvoltages onto the networks
- Grounding ensures the safe dissipation of energy to the earth .
At LPS France , we support project owners, design offices and installers in the design and implementation of complete, connected lightning protection systems compliant with IEC 62305 and NF C 17-102 standards. Contact our team for a personalized study of your installation.
