IEC 61000-4-5 Surge Testing: Immunity to Lightning Transients
The levels of IEC 61000-4-5, which measures immunity to high-energy transients from lightning and large switching on the grid, and how to protect against them.
3 min readNovember 8, 2026
Why Cables?
Radio signals between 150 kHz and 80 MHz have wavelengths from several meters to hundreds of meters. At these frequencies the device itself can't act as a small antenna; it's the long cables attached to it that actually collect the signal.
So in this range, immunity is tested not by exposing the device to a field but by injecting the signal directly into the cables. IEC 61000-4-6 defines this method and complements radiated immunity testing at lower frequencies.
The Test Setup
The signal is applied to cables using coupling-decoupling networks (CDNs) or injection clamps. CDNs pass the signal onto the cable while protecting auxiliary equipment from the disturbance. Typical test levels are 3 V and 10 V.
The signal is amplitude-modulated at 1 kHz and the frequency is swept step by step. The device stands at a set height above the reference ground plane and cables are laid out per the standard.
Is a Shielded Room Needed?
In this test energy goes into the cables, but the cables also radiate somewhat. At high levels this radiation can affect nearby equipment and radio services. That's why the test is usually done in a shielded room or shielded area.
The room doesn't need high-dB shielding or absorbers; a basic RF shielded room is often enough. That makes it possible to run the test in a much more economical space than an anechoic chamber.
Common Problems
Analog sensor inputs, long unshielded cables and audio circuits are the parts that most often cause trouble in this test. The disturbing signal is rectified at semiconductor inputs and causes the reading to drift.
Correct cable shield termination, RC filters at inputs and common-mode chokes are typical fixes. We'll cover cable shielding in detail in an upcoming article on the topic.
Frequently Asked Questions
What's the difference between a CDN and a clamp?
A CDN connects directly to the cable and gives more repeatable results; a clamp is used for cable types that have no CDN.
Does this test apply to every product?
It applies to products connected to cables that can exceed a certain length; it may not be needed for devices with very short cables.
How is the test level chosen?
The product standard and environment decide: usually 3 V for residential and 10 V for industrial.
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