Lightning strikes the Earth approximately 40 to 50 times per second (Vaisala, 2023). In parallel, the overvoltages induced by these strikes — or by the switching of the electrical network — represent the main cause of destruction of electrical and electronic equipment in industrial, commercial and residential buildings.
To address this, the international standard IEC 62305-4 (Lightning protection — Electrical and electronic systems in structures) mandates the installation of surge arresters, also known as SPDs. These devices come in three types — Type 1, Type 2 and Type 3 — with distinct roles.
Therefore, choosing the right type of surge protector is not simply a matter of range or price. It is a technical decision that determines the actual protection of your installation. This guide explains the selection criteria that every installer or engineering firm must understand.
What is a surge arrester (SPD) and what is its purpose?
A protector (SPD) is a device that limits transient overvoltages on electrical and electronic circuits by diverting the overvoltage energy to ground.
In other words, it acts like a safety valve: as soon as an abnormally high voltage appears on the network, the SPD absorbs or diverts it before it reaches your sensitive equipment.
Therefore, surge protectors provide protection, in particular:
- Electrical panels and distribution cabinets
- Computer systems, servers and networks
- Industrial automation systems (PLCs, sensors, actuators)
- Medical, telecom and measurement equipment
A surge arrester should not be confused with an early streamer emission (ESE) lightning rod, which captures the lightning itself before it reaches the structure. The two devices are complementary in a complete protection system conforming to IEC 62305.
Type 1 surge protector: the first line of defense
The Type 1 surge arrester is designed to dissipate direct lightning currents. It is sized to withstand very high current pulses, measured according to the Iimp (lightning surge current).
When to install a Type 1?
According to IEC 62305-4, a Type 1 SPD is mandatory in the following cases:
- The structure is equipped with an external lightning protection system (ESE, meshed cage, guard wire)
- The building is connected to an overhead line (LV or MV overhead network)
- The site is classified as a high lightning strike zone (high ground lightning density Ng according to IEC 62305-2)
In practice, Type 1 is installed at the network inlet, in the main low voltage switchboard (TGBT) or at the head of the installation.
Key technical specifications
- Iimp : lightning surge current in kA (typical values: 12.5 to 25 kA per pole depending on the protection class)
- Up (voltage protection level): permissible residual voltage across the SPD terminals
- Technology: Metal oxide (MOV) spark gaps or varistors
In addition, Type 1 SPDs are often referred to as "spark-gap arresters" because of their technology based on controlled electric arcs, capable of absorbing extreme energy spikes.
Type 2 surge arrester: standard protection against induced overvoltages
Type 2 surge protectors are the most common level of protection in commercial and residential installations. They are designed to absorb induced overvoltages—that is, electromagnetic disturbances resulting from nearby lightning strikes without direct impact on the structure.
When to install a Type 2?
A Type 2 SPD is required:
- In all electrical distribution panels (divisional, sub-panels)
- Downstream of a Type 1 surge arrester, to complete the protection
- When IEC 62305-4 mandates SPD protection but the installation does not have PEF (External Lightning Protection)
For example, a logistics warehouse connected by underground cable (without overhead line) does not necessarily need a Type 1, but must absolutely be equipped with Type 2 on its switchboards.
Key technical specifications
- Imax : maximum discharge current (8/20 µs) — typical values: 20 to 80 kA
- In : nominal discharge current (reference value for repeated tests)
- Up : residual voltage — crucial for protecting downstream equipment
However, Type 2 alone is not sufficient in configurations exposed to direct lightning: it must then be combined with a Type 1 upstream.
Type 3 surge protector: close protection for sensitive equipment
Type 3 surge protectors are precision protection devices installed directly as close as possible to the sensitive equipment they protect. In practice, they are found in the form of surge-protected sockets, surge protection strips for telecom networks, or modules mounted in equipment enclosures.
When to install a Type 3?
Type 3 is the final level of protection. It is recommended (and sometimes mandatory according to the IEC 62305-2 risk analysis) for:
- Computer equipment, servers, workstations
- Industrial automation and measurement sensors
- Audiovisual and security equipment (IP cameras, access control)
- Telecommunications and measurement systems with low surge immunity
Key technical specifications
- Uoc : open circuit voltage of 1.2/50 µs (usually 6 kV)
- Discharge currents lower than Type 2 (only a few kA)
- Installation must be downstream of a Type 1 or Type 2
Ultimately, Type 3 can never replace previous types: it complements SPD coordination, it does not create it.
How to choose the right type for your installation?
The selection of the appropriate SPD(s) results from a lightning risk analysis compliant with IEC 62305-2. Several criteria are taken into account:
Criterion 1 — Presence of an EFP (External Lightning Protection)
If the structure has a lightning rod (ESE) or a Faraday cage, a Type 1 SPD is mandatory at the head of the electrical panel. This is because the down conductors from the PEF can induce very high voltages in nearby electrical cables.
Criterion 2 — Type of connection to the network
- Overhead network → Type 1 mandatory (or Type 1+2 combined)
- Underground network → Type 2 is generally sufficient at the main line, + Type 3 for sensitive equipment
Criterion 3 — Ground lightning density (Ng) of the site
The Ng parameter (ground lightning density, expressed in impacts/km²/year) according to IEC 62305-2 determines the calculated risk level. The higher the Ng value, the more robust the protection measures must be. In Central Europe, values vary from 0.5 to more than 4 impacts/km²/year depending on the area.
Criterion 4 — Value and criticality of equipment to be protected
Thus, a datacenter or an industrial control station will systematically justify three coordinated levels of protection (Type 1 + Type 2 + Type 3), regardless of the conditions of lightning strike.
Criterion 5 — Coordination between levels
SPD coordination is essential: the protection levels (Up) of each type must be consistent, with short connecting cables (< 0.5 m recommended) and proper Equipotential Spark Gap. Therefore, the sizing must be carried out by a specialist engineering firm.
Comparative table: Type 1 / Type 2 / Type 3
To summarize the key selection criteria, here is a concise comparison:
| Criteria | Type 1 | Type 2 | Type 3 |
|---|---|---|---|
| Reference standard | IEC 61643-11 / IEC 62305-4 | IEC 61643-11 / IEC 62305-4 | IEC 61643-11 / IEC 62305-4 |
| Dimensioning parameter | Iimp (kA) | Imax / In (kA) | Uoc (kV) |
| Position in the installation | Main distribution board / network incoming | Subdivision tables | Proximity to equipment |
| Obligation if PEF | ✅ Yes | ✅ Downstream Type 1 | ✅ Recommended |
| Use alone? | Yes (if PEF) | Yes (without PEF, underground network) | ❌ No — always downstream |
LPS France surge protectors: a complete range for every level
LPS France offers a range of surge protectors covering all three types, for residential, commercial, and industrial applications. Our surge protectors comply with IEC 61643-11 standards and the requirements of IEC 62305-4.
In addition, our technical teams support design offices and installers in the choice and sizing of SPDs, integrating the site risk analysis according to IEC 62305-2.
For any questions regarding the selection of surge arresters suitable for your project, please contact our technical team.
Manage the monitoring of your lightning protection installations with LPS Manager
Once your SPD installation is in place, monitoring its compliance and maintenance over time is just as important as the initial choice of equipment.
This is precisely what LPS Manager : software for managing lightning protection files, planning periodic checks and monitoring IEC 62305 compliance across all your sites.
Therefore, every cartridge replacement, every annual inspection, and every lightning event at your sites can be tracked, documented, and planned via the platform. Discover LPS Manager.
In summary: which surge protector should you choose?
In conclusion, the choice between Type 1, Type 2, and Type 3 surge protectors is not a matter of product range, but of installation context. To summarize the key points:
- Type 1 is essential if the installation is equipped with a ESE or connected via overhead lines.
- Type 2 is the standard level of protection, installed on each distribution board.
- Type 3 provides additional protection closest to sensitive equipment
- Coordination between levels is just as important as choosing each type individually .
- A risk analysis compliant with IEC 62305-2 is the basis of any correct sizing
Therefore, consult a certified engineering firm for every lightning protection project. The IEC 62305 standard is international: it applies equally in Europe, Africa, the Middle East, and South America—wherever lightning poses a risk to your installations.
