IEC 60364-5-534

How to select surge protection Type 1, 2 and 3?

Q: Is surge protection mandatory?

For new installations IEC 60364-5-534 requires surge protection wherever surges could endanger people, services or valuable equipment. In practice this applies to almost all new builds and refurbishments.

Surge protective devices (SPDs) of Type 1, 2 and 3 form a staged protection concept from the building entrance to the end device. This guide explains selection to IEC 60364-5-534, energy coordination of the SPDs, the voltage protection level Up and the correct back-up fuse.

5 minStand: 2026-07Geprüft: Technical editors

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Type 1/2/3

staged protection classes

Iimp 25 kA

lightning current (10/350) Type 1

Up ≤ 1.5 kV

protection level at end device

≥ 10 m

coordination length or decoupling

Inhalt

The three types
Selecting the SPD
Energy coordination
Back-up fuse and mounting
Frequently asked questions

What sets Type 1, 2 and 3 apart?

The three SPD types cover different stresses. Type 1 discharges the direct lightning current with the 10/350 µs waveform, Type 2 protects against induced surges and switching transients using the 8/20 µs test wave, and Type 3 sits directly in front of the end device to trim the residual protection level.

Type 1 is rated by the impulse current Iimp (for example 12.5 kA or 25 kA per pole, 10/350 µs), Type 2 by the nominal discharge current In and the maximum discharge current Imax (8/20 µs). Type 3 uses a combination wave of 1.2/50 µs voltage and 8/20 µs current.

For buildings with an external lightning protection system (LPS) or an overhead line supply, a Type 1 SPD is mandatory. Without external lightning protection a Type 2 device at the incomer is usually sufficient.

How do you select the right SPD?

The key factors are the earthing system (TN-S, TN-C-S, TT), the continuous voltage Uc and the protection level Up. Uc must exceed the highest continuously expected operating voltage, and in TT systems the N-PE path often needs higher ratings.

Determine the earthing system: TN-S/TN-C-S with 4 discharge paths (3+N), TT often in a 3+1 arrangement with an N-PE spark gap.
Choose Uc: at least 253 V for a 230/400 V network, up to 260 V for the N-PE path in TT.
Watch the protection level Up: keep it low so the equipment insulation (overvoltage category) stays safely below it.
Split the impulse current Iimp according to the LPS class and the number of conductors.
Prefer a device with a remote signalling contact for status monitoring inside the panel.

For end devices the overvoltage category to IEC 60664‑1 applies: 230/400 V socket circuits need a rated impulse withstand voltage of 2.5 kV (Cat. II). The chain protection level Up should stay well below this, ideally Up ≤ 1.5 kV at the end device.

Panel build

Arrange SPDs, back-up fuse and wiring correctly inside the distribution board.

Read the guide

How do you coordinate the protection stages?

The SPDs must be energy coordinated: Type 1 takes the main energy, while Type 2 and Type 3 should only fire once the upstream device has diverted most of the current. Without coordination the finer device is overloaded and destroyed.

As a rule of thumb, keep a cable length of at least 10 m between Type 1 and Type 2, and around 5 m between Type 2 and Type 3. If the distance is shorter, a decoupling inductor or a manufacturer-tested combined Type 1+2 arrester provides the coordination.

Short connecting leads are essential: the sum of the supply and discharge lead to the SPD should not exceed 0.5 m, because every bit of cable inductance raises the effective protection level (an added voltage of roughly 1 kV per metre).

Which back-up fuse and wiring are required?

Every SPD needs an overcurrent protective device (back-up fuse) if the existing fuse exceeds the maximum value stated by the manufacturer. If the mains fuse is equal to or smaller than the stated maximum, a separate back-up fuse can be omitted.

Check the datasheet: maximum back-up fuse for example 125 A gG for Type 1 arresters, 63‑125 A gG for Type 2.
Connect to the main earthing bar with adequate cross-section: Type 1 at least 16 mm² Cu, Type 2 at least 6 mm² Cu.
Prefer V-wiring (through-wiring) to keep the connections short and low in inductance.
Use the status indicator and remote contact for maintenance and documentation.
Plug-in protection modules make replacement after a lightning event easy without rewiring.

To IEC 60364‑5‑534, surge protection must be provided for new installations wherever surges could endanger people, services or high-value equipment - which in practice covers nearly every new installation.

Frequently asked questions

Do I need Type 1 if there is no lightning protection?

A Type 1 SPD is required when the building has an external lightning protection system (LPS) or is fed by an overhead line. Without these conditions a Type 2 device at the incomer is usually enough.

Can I combine Type 1 and Type 2 in one device?

Yes, combined Type 1+2 arresters are permitted and internally coordinated. They save space and replace the 10 m coordination run, provided the manufacturer has tested the combination.

How long may the connecting lead to the SPD be?

The sum of the supply and discharge lead should not exceed 0.5 m. Every additional metre raises the effective protection level by around 1 kV due to cable inductance.

Is surge protection mandatory?

For new installations IEC 60364‑5‑534 requires surge protection wherever surges could endanger people, services or valuable equipment. In practice this applies to almost all new builds and refurbishments.

Surge protection for your distribution board?

We supply coordinated Type 1, 2 and 3 arresters, combination devices and matching back-up fuses - engineered to IEC 60364-5-534.

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Standard compliant

Arresters to IEC 61643-11 and IEC 60364-5-534.

Tested discharge capacity

Iimp and Imax documented per datasheet.

Energy coordinated

Type 1, 2 and 3 cleanly matched to each other.

Expert advice

Our specialists help you size the protection.