What is the difference between Surge IEC 61000-4-5 and EFT/Burst IEC 61000-4-4?

Both standards simulate conducted transients but reproduce distinct physical phenomena. Surge IEC 61000-4-5 reproduces the single high-energy pulse arising from an indirect lightning strike or a power network switching event, with a combination wave of 1.2/50 us in open-circuit voltage and 8/20 us in short-circuit current. EFT/Burst IEC 61000-4-4 reproduces the repetitive burst of fast transients generated by switching inductive loads (relays, contactors), with 5/50 ns pulses repeated at 5 kHz or 100 kHz during 15 ms bursts every 300 ms. Surge carries more energy per pulse, Burst covers a much wider spectral band.

What severity levels apply to a residential product?

For AC power ports of a product intended for residential, commercial or light industrial environments (EN 55035, EN 55024), the default levels are 2 kV common mode and 1 kV differential mode for Surge, and 1 kV on EFT/Burst at the power port. Long signal ports (longer than 3 m) receive 1 kV common mode for Surge and 0.5 kV for EFT/Burst through the capacitive clamp. These levels match Class 3 in the normative table and remain the common regulatory minimum in Europe.

Why does the telecom port use a 10/700 us wave instead of 1.2/50 us?

Outdoor telecom lines are long and exposed to direct or induced lightning strikes over kilometre-scale distances. The 10/700 us voltage wave (5/320 us in current), derived from ITU-T Recommendations K.20 and K.21, models the actual profile of a lightning surge attenuated by the line. The associated source impedance is 40 ohm and the level can rise to 4 kV. This wave replaces the classic combination wave for telecom ports and is described in the corresponding annex of IEC 61000-4-5.

What is the capacitive coupling clamp and when is it used?

The capacitive coupling clamp is a metallic structure in two half-shells through which the signal cable under test is fed. It provides a distributed capacitive coupling of around 50 to 200 pF between the burst generator and the cable bundle, without galvanic contact. It is specified by IEC 61000-4-4 for EFT/Burst application to signal and control ports whose connectors do not lend themselves to direct CDN injection. Its position and orientation above the ground reference plane are standardised and reproducible.

What do performance criteria A, B and C mean?

Criteria define the expected behaviour of the product during and after the disturbance. Criterion A, normal operation during the stress, no degradation beyond declared tolerances. Criterion B, temporary degradation during the stress, automatic return to normal operation without intervention. Criterion C, loss of function accepted during the stress, recovery through operator intervention (power cycle, reset). The applicable criterion depends on the port type and product standard, EN 55035 typically requires B for AC Surge and A or B for EFT/Burst.

How does ISO 7637-2 differ for automotive products?

ISO 7637-2 covers conducted transients on the 12 V or 24 V on-board network of a road vehicle. The pulse profiles differ (pulses 1, 2a, 2b, 3a, 3b among others, simulating load-dump, inductor switching, starter), the levels reach hundreds of volts in transient and the source impedance is lower (typically 10 ohm). The principle of conducted transient stress is analogous to IEC 61000-4-4 and 4-5, but the waveforms and severities reflect the physics of the automotive on-board network. A product certified under IEC 61000-4-5 must be re-evaluated against ISO 7637-2 for vehicle use.

How many Surge pulses are required and at what polarity?

IEC 61000-4-5 requires at least five positive and five negative pulses per test condition, with a minimum spacing of one minute between pulses to let the protection elements (varistors, gas tubes) discharge and thermally reset. The pulses are synchronised to mains phase at 0, 90, 180 and 270 degrees for AC ports, to capture the worst combination of wave energy and instantaneous network voltage. The total pulse count for a single-phase AC port thus reaches 40 pulses per level.

What are the most frequent test report errors?

Four causes recur. Wrong port classification (an ethernet port declared as a short signal port when it serves an outdoor cable and should undergo the telecom 10/700 us test). A CDN not matched to the port impedance. A non-compliant capacitive clamp position (distance to the ground plane, coupling length, cable termination). Omission of mains-phase synchronised pulses. Each leads to a notified body report rejection or a return to the lab at a typical extra cost of 1 500 to 4 000 EUR per additional session.

Surge and Burst (IEC 61000-4-5 / 4-4): EMC transients

Author Hugues Orgitello Last updated 27 May 2026 ~14 min read

Guide · Conducted transient EMC immunity

Surge IEC 61000-4-5 and EFT/Burst IEC 61000-4-4 form the core of conducted transient immunity in the EMC reference framework. Mandatory for any product placed on the European market under EMC Directive 2014/30/EU, they are referenced by EN 55035 (multimedia equipment), EN 55024 (information technology equipment), EN 60601-1-2 (medical devices) and many vertical product standards. This page details waveforms, severity levels per class and port type, coupling and decoupling networks, the metrology of the capacitive clamp, performance criteria A, B and C, and the classic pitfalls observed in pre-compliance.

Why two distinct tests

Surge and Burst represent two physical families of conducted transients that any electronic product connected to mains or to external cables must face. Separating them is a deliberate IEC committee choice, their energy, duration and coupling mechanism differ too much for a single standard to cover both.

Surge (IEC 61000-4-5). Single high-energy pulse, typically arising from induced lightning on the network or from distribution transformer switching. Slow waveform (microseconds), high energy, capable of destroying components if protection is insufficient.
EFT/Burst (IEC 61000-4-4). Repetitive burst of very fast pulses originating from inductive load switching (relays, contactors, motors, industrial lighting). Fast waveform (nanoseconds), low individual energy but wide spectrum extending to several hundred megahertz, capable of disturbing logic on digital links.

A product can be robust against one and vulnerable to the other. Protection mechanisms differ, varistors and gas tubes for Surge, decoupling capacitors and common-mode chokes for Burst. This is why both tests are systematically combined in harmonised EMC standards.

IEC 61000-4-5: the Surge test

Scope and ports concerned

IEC 61000-4-5 applies to the following ports of an electrical or electronic equipment.

Port type	Typical coupling	Source impedance	Default waveform
AC power	Capacitive coupling through coupling/decoupling network (CDN)	2 ohm	Combination 1.2/50 us + 8/20 us
DC power	Capacitive coupling through CDN	2 ohm	Combination 1.2/50 us + 8/20 us
Short symmetrical signal port (under 30 m)	CDN type S	42 ohm	Combination 1.2/50 us + 8/20 us
Outdoor telecom port	Dedicated CDN	40 ohm	10/700 us and 5/320 us
Ethernet link > 30 m	Ethernet CDN or clamp per product standard	42 ohm	Combination 1.2/50 us + 8/20 us or telecom variant

Ports strictly internal to an enclosure (internal bus between two adjacent boards) are not concerned. The practical rule, any port that may connect a cable leaving the enclosure must be evaluated.

The 1.2/50 us and 8/20 us combination wave

The Surge generator, called Combination Wave Generator (CWG), simultaneously produces two profiles depending on the load.

Open circuit (high impedance). Pulsed voltage with 1.2 us rise time and 50 us duration at half amplitude. This is the nominal test voltage.
Short circuit (low impedance). Pulsed current with 8 us rise time and 20 us duration at half amplitude. This is the nominal test current.

The ratio of open-circuit voltage to short-circuit current defines the source impedance of the generator, fixed at 2 ohm for power ports. The same pulse thus becomes a voltage test for a product with high input impedance and a current test for a product with low input impedance. The CWG is calibrated individually and its calibration certificate is part of the test dossier.

For short signal ports, the CDN adds a series impedance bringing the effective source impedance to 12 ohm (high-impedance signal port) or 42 ohm (symmetrical signal port).

For outdoor telecom ports, the waveform switches to 10/700 us in voltage and 5/320 us in current, with a source impedance of 40 ohm, described in the corresponding annex of the standard and aligned with ITU-T Recommendations K.20 and K.21 for the resistibility of telecommunication equipment in a telecommunication centre.

Severity levels Class 1 to 4

The normative levels are organised in four classes corresponding to increasingly severe environments.

Class	Typical environment	Line-to-ground level (common mode)	Line-to-line level (differential mode)
1	Well-protected environment (lab, controlled room)	0.5 kV	not applicable
2	Partially protected environment (standard office)	1 kV	0.5 kV
3	Moderate industrial, residential and commercial	2 kV	1 kV
4	Severe industrial, long outdoor lines	4 kV	2 kV
X	Open class, value to be specified by product standard	To be defined	To be defined

For a consumer product or multimedia equipment under EN 55035, the typical AC-port target is Class 3 (2 kV common mode, 1 kV differential mode). For a medical device under EN 60601-1-2 edition 4, the AC port typically rises to 2 kV common mode and 1 kV differential mode, with mandatory criterion B and preferred criterion A.

Pulse count, polarity and phase

The application methodology is specified precisely by IEC 61000-4-5.

Five positive pulses and five negative pulses per level and per test condition, ten pulses minimum.
Minimum one-minute spacing between consecutive pulses to allow varistors, gas tubes and other protection elements to thermally reset.
Mains-phase synchronisation for AC ports, pulses applied at 0, 90, 180 and 270 degrees of the sine wave. The 270-degree phase is the worst case for a product whose rectifier diode conducts at the zero crossing.

For a single-phase AC port, the total typically reaches 40 pulses per level (5 positive polarity x 4 phases + 5 negative polarity x 4 phases). For a DC port, mains-phase synchronisation does not apply and the total stays at 10 pulses per level.

Coupling and decoupling networks (CDN)

The CDN fulfils two critical simultaneous functions.

Coupling. Inject the generator pulse onto the line of the equipment under test (EUT) at the desired point (line-ground, line-line).
Decoupling. Prevent the pulse from feeding back into the upstream mains and into other lab equipment.

Decoupling is performed by common-mode and differential-mode chokes sized to block the high-frequency component of the pulse. An undersized CDN (impedance too low, parasitic capacitance too large) lets energy leak upstream, which falsifies the voltage actually applied to the EUT and invalidates the measurement. CDN selection depends on port type, nominal network voltage, maximum current and conductor count, and is documented in the report.

IEC 61000-4-4: the EFT/Burst test

Scope and ports concerned

IEC 61000-4-4 applies to power, earth, signal and control ports of any electrical or electronic equipment. The functional earth port is tested only when the manufacturer explicitly declares it as a product function (chassis earth, not via the PE conductor).

The 5/50 ns waveform in bursts

The individual Burst pulse has the following characteristics.

Parameter	Normative value
Rise time	5 ns +/- 30 %
Duration at half amplitude	50 ns +/- 30 %
Repetition frequency	5 kHz or 100 kHz (per revision and level)
Burst duration	15 ms
Period between bursts	300 ms
Total application duration per polarity	1 minute minimum
Generator source impedance	50 ohm

A 15 ms burst at 100 kHz contains 1 500 pulses, and the test sequence applies this burst every 300 ms for at least one minute. The total reaches several thousand bursts per polarity, several million individual pulses end to end.

The 2012 edition of the standard introduced the choice between 5 kHz and 100 kHz as repetition frequency. The 100 kHz frequency is preferred for modern tests because it better reflects the fast switching observed on modern power networks (variable-frequency drives, switching power supplies). Some older product standards still reference the historical 5 kHz.

Severity levels Class 1 to 4

Class	Typical environment	Power port level	Signal port level
1	Well-protected environment	0.5 kV	0.25 kV
2	Protected environment	1 kV	0.5 kV
3	Moderate industrial, residential	2 kV	1 kV
4	Severe industrial	4 kV	2 kV
X	Open class	To be defined	To be defined

For a residential or multimedia product (EN 55035), the typical target is Class 3 on the power port (2 kV) and Class 2 on long signal ports (0.5 kV). A medical device under EN 60601-1-2 typically goes to 2 kV power and 1 kV on signal ports longer than 3 m.

Direct coupling and capacitive clamp

The Burst pulse is coupled to the EUT through two methods depending on port type.

Direct coupling through CDN. Used for power ports. The CDN injects the pulse on each conductor in turn and on all conductors in common mode. Internal CDN coupling impedance is typically 33 nF.
Capacitive coupling through the clamp (capacitive coupling clamp). Used for signal and control ports whose connectors do not lend themselves to direct injection (ethernet, RS-485, audio, video). The clamp is a metallic structure in two half-shells closed around the cable, providing a distributed capacitance of 50 to 200 pF between the clamp body and the inner bundle. This capacitance distributed along the clamp length (typically 1 m) couples the pulse without galvanic contact.

The clamp position is standardised, 0.1 m above a ground reference plane, with the EUT cable leaving at 90 degrees to the main clamp axis and a termination on the EUT side at the product interface. An incorrect position introduces impedance variability that can exceed a factor of 2 on the level actually applied.

EFT/Burst performance criteria

For EFT/Burst, criterion B is the default in current harmonised EMC standards (EN 55024, EN 55035, EN 60601-1-2). The product may show temporary disturbance during the burst but must return to nominal operation without intervention after application ends. Temporary data loss is generally accepted, configuration loss or a reset is rarely accepted.

Synthesis: Surge vs Burst vs ESD

To place these two tests in the IEC 61000-4 panorama of conducted and radiated immunity, the table below compares the three most frequent transient tests.

Test	Standard	Waveform	Physical mechanism simulated	Typical coupling	Typical Class 3 level
ESD (electrostatic discharge)	IEC 61000-4-2	0.7-1 ns / 60 ns	Discharge from an operator or charged object	Contact or air, by hand-held probe	4 kV contact, 8 kV air
EFT/Burst	IEC 61000-4-4	5/50 ns in bursts	Inductive load switching on the network	CDN or capacitive clamp	2 kV power, 1 kV signal
Surge	IEC 61000-4-5	1.2/50 us voltage, 8/20 us current	Induced lightning, transformer switching	CDN, capacitive or direct	2 kV common mode, 1 kV differential mode

Reading, ESD acts on very short time scales (sub-nanosecond) and high voltage levels but with low total energy. EFT/Burst acts on short time scales (nanosecond) repeated in bursts to excite the spectral band up to several hundred megahertz. Surge acts on long time scales (microsecond) with high unit energy capable of destroying an unprotected component. The three tests are systematically combined in a complete EMC campaign.

See RED tests for the panorama of EMC tests applicable under the RED directive, and CE tests for EMC directive 2014/30/EU.

The IEC 61000-4 family: placing Surge and Burst

Surge and Burst are two entries in the IEC 61000-4 chapter dedicated to immunity test techniques. The table below places the conducted tests and their direct neighbours.

Standard	Phenomenon	Test type
IEC 61000-4-2	ESD	Conducted, point-like
IEC 61000-4-3	Radiated RF field	Radiated
IEC 61000-4-4	EFT/Burst	Conducted transient
IEC 61000-4-5	Surge	Conducted transient
IEC 61000-4-6	Conducted RF	Conducted, low frequency
IEC 61000-4-8	50/60 Hz magnetic field	Radiated
IEC 61000-4-11	Voltage dips and interruptions	Conducted, mains
IEC 61000-4-12	Damped oscillatory waves	Conducted transient

IEC 61000-4-12 (Ring Wave) is less often required in European harmonised standards but remains applicable for some North American industrial environments and for power ports downstream of HV/LV transformers. The two variants (damped oscillatory wave at 100 kHz and 1 MHz) reproduce the so-called damped oscillatory wave transients characteristic of switching in electrical substations.

ISO 7637-2 and the automotive case

For a product intended for a road vehicle on-board network, IEC 61000-4-5 and IEC 61000-4-4 do not apply directly. The reference standard becomes ISO 7637-2, which defines its own pulses characteristic of automotive physics.

ISO 7637-2 pulse	Simulated phenomenon	Peak level
Pulse 1	Switching of an inductive load in parallel with EUT	-75 to -150 V
Pulse 2a	Interruption of a current in nearby wiring	+37 to +112 V
Pulse 2b	Contact interruption after engine stop	+10 V (attenuated DC)
Pulse 3a / 3b	Fast bursts similar to EFT/Burst	-150 to +100 V
Pulse 4	Starter (slow voltage variation)	-7 V
Pulse 5a / 5b	Load dump (battery disconnect with alternator loaded)	up to +87 V peak

Pulse 5b in particular (load dump with alternator protection) remains the on-board network worst case and drives the input protection sizing of any automotive electronic module. A product certified to IEC 61000-4-5 at 2 kV is never automatically certified to ISO 7637-2, the physics of automotive transients does not share the same energy profile nor the same source impedance. A dedicated campaign is required.

Classic campaign preparation pitfalls

Rejections observed in EMC labs come overwhelmingly from a few recurring causes.

Wrong port classification. An ethernet port declared as a short signal port when it serves an outdoor or building cable should undergo the telecom 10/700 us test, not the classic 1.2/50 us combination. Classification appears in the test plan and drives the CDN, waveform and level. An error here invalidates the entire campaign on that port.
CDN not matched to port impedance and current. The CDN must be selected for conductor count, nominal voltage, maximum current and frequency (50 Hz, 60 Hz, DC). An undersized CDN heats up and drifts in impedance, an oversized CDN has excessive parasitic capacitance that attenuates the pulse. The report must cite the model and calibration certificate of the CDN used.
Non-compliant capacitive clamp position. Distance to the ground plane, coupling length, EUT cable termination, isolation of other cables, each parameter is specified by IEC 61000-4-4. A deviation introduces impedance variability that can reach a factor of 2 on the level actually applied to the cable. A photo of the clamp setup is required by some notified bodies.
Source-impedance confusion. Surge uses 2 ohm on AC, 12 ohm on high-impedance signal, 42 ohm on symmetrical signal and 40 ohm on telecom. EFT/Burst uses 50 ohm. A test run with the wrong source impedance does not reflect the intended physical scenario and is non-compliant with the standard. The most frequent error is using the signal CDN for a test intended for power ports, which underestimates the energy actually delivered.
Omission of mains-phase synchronisation. For Surge tests on AC ports, pulses must be injected at 0, 90, 180 and 270 degrees of the mains sine wave. A test run in asynchronous mode (random pulse phases) does not cover the worst case and is non-compliant with the normative procedure. The Surge generator must therefore feature a mains synchronisation input or an internal phase sensor.

Articulation with the EMC and RED directives

Within the European Union, Surge and Burst are referenced in all harmonised EMC immunity standards listed in the OJEU for directives 2014/30/EU (EMC) and 2014/53/EU (RED).

EN 55035 (residential and commercial multimedia equipment), Surge 2 kV / 1 kV on AC, EFT/Burst 1 kV on AC, 0.5 kV on signals.
EN 55024 (information technology equipment, transitioning to EN 55035), identical levels.
EN 60601-1-2 edition 4 (medical devices), Surge 2 kV / 1 kV, EFT/Burst 2 kV / 1 kV, typically stricter criteria (A preferred).
EN 61000-6-1 (generic immunity residential/commercial/light industrial), Surge 1 kV / 0.5 kV, EFT/Burst 1 kV / 0.5 kV.
EN 61000-6-2 (generic immunity industrial), Surge 2 kV / 1 kV, EFT/Burst 2 kV / 1 kV.

Selection of the applicable product standard depends on product classification. The generic EN 61000-6-x standard applies in the absence of a dedicated vertical standard. See the Glossary for the definitions of the terms used here (CDN, EFT, Surge, criteria A/B/C).

Indicative schedule

To plan a Surge and Burst campaign integrated into an EMC dossier, here are the orders of magnitude observed in a European ISO/IEC 17025 accredited laboratory.

Configuration	4-4 + 4-5 campaign duration
Single-port AC product, no long signals	0.5 to 1 day
AC + 2 to 4 short signal ports	1 to 2 days
AC + signals + 10/700 us telecom port	2 to 4 days
EN 60601-1-2 medical device, multi-mode	3 to 5 days
Class 4 industrial equipment	2 to 4 days

Duration depends on the number of ports to test, the target level (Class 4 requires more powerful generators that are scarcer in the lab fleet) and the number of operating modes to cover for criteria A and B.

Takeaways

Surge IEC 61000-4-5 and EFT/Burst IEC 61000-4-4 are the two conducted transient immunity tests required by every European product EMC standard.
Surge. Single pulse 1.2/50 us (voltage) and 8/20 us (current), impedance 2 ohm AC, 12-42 ohm signal, 40 ohm telecom (10/700 us). Levels 0.5 to 4 kV per class.
EFT/Burst. Repetitive bursts 5/50 ns at 5 kHz or 100 kHz, 15 ms per burst every 300 ms. Levels 0.25 to 4 kV per class and port. Source impedance 50 ohm.
Coupling. Dedicated CDN for power and some signals, capacitive clamp for signals not suited to direct injection.
Performance criteria A (no degradation), B (temporary degradation with automatic recovery), C (loss accepted with operator intervention). Criterion B is the common default.
ISO 7637-2 replaces Surge and Burst for automotive products. Pulses specific to the 12 V / 24 V on-board network, levels reaching hundreds of volts in transient, lower source impedance.
Classic pitfalls. Port classification, CDN mismatch, capacitive clamp position, source-impedance confusion, omission of mains-phase synchronisation.

For the EMC directive context, see CE tests. For RED health and EMC tests, see RED tests. For the definitions of terms used here, see the Glossary.

Surge and Burst (IEC 61000-4-5 / 4-4): EMC transients

Why two distinct tests

IEC 61000-4-5: the Surge test

Scope and ports concerned

The 1.2/50 us and 8/20 us combination wave

Severity levels Class 1 to 4

Pulse count, polarity and phase

Coupling and decoupling networks (CDN)

IEC 61000-4-4: the EFT/Burst test

Scope and ports concerned

The 5/50 ns waveform in bursts

Severity levels Class 1 to 4

Direct coupling and capacitive clamp

EFT/Burst performance criteria

Synthesis: Surge vs Burst vs ESD

The IEC 61000-4 family: placing Surge and Burst

ISO 7637-2 and the automotive case

Classic campaign preparation pitfalls

Articulation with the EMC and RED directives

Indicative schedule

Takeaways

See also