¿Cuáles son los diferentes tipos de sistemas de protección contra los rayos?

There are four types of lightning protection system in common use: the Franklin rod, the meshed cage, the catenary (taut wire) system, and the early streamer emission (ESE) air terminal. The first three are passive — they present a preferred strike point and let the lightning find it. The fourth is active — it tries to launch an upward streamer earlier than the surrounding structure would.

That is the short answer. The longer answer is that the choice between them is not a matter of brand preference. It follows from three things: the protection level your structure needs under IEC 62305, the geometry of the building, and which standard the local authority actually enforces. A system that is correct in France may be rejected in the United States, and a system that looks adequate on a small house is not adequate on a 60 m warehouse.

This guide covers all four types, the protection levels that determine their size, the three design methods used to lay them out, and the part most articles skip — the surge protection that has to sit behind the air termination, because a lightning protection system without SPDs still lets induced surges destroy the equipment inside.

Types of Lightning Protection Systems

Conventional Systems (Standard NF EN 62-305)

1. Franklin Rod
Developed by Jacques de Romas and Benjamin Franklin, the Franklin rod is a traditional lightning protection method. It consists of a metal rod installed at the highest point of a building and connected to the ground via down conductors.

Its protection zone is not a fixed radius. Under IEC 62305-3 the zone is derived from the protection level and the rod height — a 5–6 m mast on a house under LPL III typically covers something in the order of ten metres of radius, not the flat “30 m” figure that gets repeated in a lot of online material. Height buys you coverage, but with diminishing returns, and each added metre is another metre of mast that has to survive wind load.

Advantages:

• Simple installation
• Cost-effective for small projects
• Can be integrated discreetly in some structures

Disadvantages:

• Limited coverage — the protected zone shrinks as the structure gets wider
• Needs one rod (or a small cluster) per protected zone, so a large roof needs many
• Mast strength and wind loading become the limiting factor on tall exposed sites

Best for: Antennas, small houses, small churches, chimneys, single tanks

Standards: IEC EN 62561 (components), IEC EN 62305-3 (installation)

2. Meshed Cage
Based on the Faraday cage principle, this system surrounds the building with a conductive mesh on the roof and walls. It is connected to grounding loops, and lightning rods may be placed at strategic points. Smaller mesh sizes provide higher levels of protection.

Advantages:

• Reduces electromagnetic effects inside the building
• Maintains equipotentiality between the structure and earth
• Works on any footprint, including complex or stepped roofs

Disadvantages:

• Complex installation
• Higher material and labor costs
• Visually prominent on finished facades unless designed in from the start

Best for: Data centers, sensitive electrical installations, laboratories, ammunition and hazardous stores

Standards: IEC EN 62561, IEC EN 62305-3

3. Catenary (Taut Wire) Lightning Conductors
These systems function similarly to meshed cages but are installed above the building, at a distance. Conductive wires are held under tension and connected to grounding points, capturing lightning before it reaches the structure.

Advantages:

• Reduces electromagnetic impact inside the building
• Protects open areas that have no roof to mount a rod on
• Maintains equipotentiality

Disadvantages:

• Installation complexity
• Higher costs
• Visually more noticeable

Best for: Outdoor storage, tank farms, industrial yards, launch pads, substation switchyards

Standards: IEC EN 62561, IEC EN 62305-3

Modern Systems (NF C 17-102)

Early Streamer Emission (ESE) Air Terminal
Originating in France in the 1980s, the ESE system generates an ascending electrical streamer that triggers a lightning strike earlier. This allows the terminal to capture lightning at a higher point and protect a larger area.

There are two types: electronically triggered, which ionizes the air to attract lightning, and geometrically triggered, which relies on the terminal’s shape to guide strikes.

Advantages:

• Captures lightning sooner
• Covers a larger protection area per terminal, so fewer masts on a large roof
• Suitable for taller or complex structures

Disadvantages:

• Small projects are slightly less economical
• Strict requirements for the grounding system (ground resistance typically below 10 Ω)
• High requirements for structural mechanics
• Not recognised everywhere. ESE is covered by NF C 17-102 in France and UNE 21186 in Spain. IEC 62305 and UL 96A do not adopt the enhanced protection radius, so a project in the US or one specifying IEC only will normally be designed with passive air termination instead

Standards: NF C 17-102, UNE 21186

Lightning Protection Systems Comparison Table

What a Complete System Has to Do

Air terminals are the visible part, but they are only one of five elements. IEC 62305 treats lightning protection as a system, and leaving out any one of the five is how buildings end up with a rod on the roof and a burnt-out BMS in the basement.

1. Air termination — rods, mesh or catenary wires that intercept the strike.
2. Down conductors — the path from the air termination to earth. Spacing is set by the protection level: roughly 10 m for LPL I and II, 15 m for LPL III, 20 m for LPL IV.
3. Earth termination — a ring or rod electrode system. IEC 62305-3 works to a low earthing resistance, and a common project target is 10 Ω or less; NF C 17-102 makes 10 Ω a firm requirement for ESE.
4. Equipotential bonding — tying metallic services, cable shields, pipes and structural steel to the same earth so that no dangerous potential difference appears inside the building.
5. Surge protective devices — the part that handles what bonding alone cannot. This is covered further down.

When a client asks for a quote on “lightning protection”, the useful question is which of these five already exist. Replacing or extending a partial system is a different job from building one from scratch, and the material list looks nothing alike.

IEC 62305 Protection Levels: LPL I to IV

IEC 62305 does not define “good” and “bad” protection. It defines four lightning protection levels, and the level decides how dense the air termination and down conductor network has to be. The level is chosen from a risk assessment — structure height, occupancy, consequence of failure, and local flash density.

Two practical consequences. First, “we installed a lightning rod” says nothing about protection level — a single rod on a 40 m wide roof is not an LPL II design no matter how tall the rod is. Second, the same building can justify LPL II in one country and LPL III in another, because the risk assessment inputs differ. That is why the risk calculation, not the drawing, is the document that decides the bill of materials.

Three Design Methods in IEC 62305-3

There are three accepted ways to position air terminations. They are not interchangeable on the same structure — each suits a different geometry.

Rolling Sphere Method

A sphere of radius r (from the table above) is rolled over the structure. Any surface the sphere can touch needs protection; anything it cannot reach is inside the protected volume. This is the most general method and the one that works for irregular shapes, because it accounts for strikes entering from the side as well as from above.

Protection Angle Method

A protected cone is drawn under each air terminal, with the half-angle α taken from the standard for the given protection level and height. It is quick to apply on simple, compact structures. It has a hard limit: above a certain height the angle becomes unusable, which is why the standard caps its application and requires the rolling sphere method instead on tall masts.

Mesh Method

Conductors are laid in a grid over the roof surface at the spacing given for the protection level. It is the most predictable method for flat and low-pitch roofs, and it is the method behind the meshed cage type described earlier. A designer can mix methods — mesh on the flat roof, rolling sphere to check the plant room and the lift overrun.

Direct Strike vs Induced Surge: Why You Need SPDs Too

A lightning protection system solves one problem: it stops a direct strike from setting the structure on fire or killing someone. It does not stop the second problem.

When lightning strikes the ground or a nearby structure, the electromagnetic field couples a surge onto every conductor in the area — mains, data, telephone, CCTV, the 24 V supply to a PLC. A building with a perfectly installed Franklin rod and no surge protection will still lose drives, controllers and power supplies, and the failure pattern usually looks random: the same line fails every storm season while the equipment next to it survives.

That is why IEC 62305-4 exists as a separate part of the standard. It introduces lightning protection zones (LPZ): the further a conductor runs into the building and the more boundaries it crosses, the more the surge energy has to be stepped down. In practice that means a SPD tipo 1 at the service entrance where the incoming line enters LPZ 1, SPD de tipo 2 at distribution boards, and Tipo 3 at sensitive equipment.

For the device side — Type 1/2/3 selection, current ratings, and how the SPD coordinates with the upstream breaker — the surge protection device range covers AC and DC versions for panel, DIN-rail and photovoltaic use, and the Type 1, 2 and 3 guide walks through the selection criteria in detail.

Matching the System to the Building

Common Design and Installation Mistakes

• Sizing the rod by height instead of by protection level. A taller rod is not a better design; the protection level decides the zone, and past a certain height the angle method no longer applies at all.
• One down conductor on a wide roof. Down conductors are spaced by protection level. A single conductor on a 30 m roof means the current has a long, inductive path with a large potential difference along it.
• Forgetting to bond the incoming services. Water, gas, telecom and the cable shield all enter the building. If they are not bonded to the same earth, the strike voltage appears between them and the equipment they connect to.
• Treating SPDs as optional. The most expensive failures are rarely the direct strike — they are the induced surges that a rod was never designed to stop.
• No inspection interval. Conductors corrode, clamps loosen, and SPD cartridges reach end of life silently unless the status window is actually read. An annual check is the normal baseline, and a system that has taken a strike should be checked immediately.

Standards Reference

Preguntas frecuentes

GA&DA Electric manufactures surge protective devices and circuit protection for AC distribution and photovoltaic systems. If you are specifying the electrical side of a lightning protection scheme, send the system voltage, earthing arrangement, protection level and the equipment you need to protect — we will return a Type 1 / Type 2 combination that matches, with the ratings written out.