What is the difference between HEMP, IEMI and a lightning surge?

HEMP is the electromagnetic pulse of a nuclear detonation at high altitude; Executive Order 13865 places it at approximately 40 km or more above the Earth. IEC 61000-2-11 classifies its early-time, intermediate-time and late-time environments, and IEC 61000-2-9 and IEC 61000-2-10 describe the radiated and conducted environments. IEMI is intentional electromagnetic interference from a deliberately operated source, covered by IEC 61000-4-36. A lightning surge is the ordinary IEC 61000-4-5 test. The three are specified in different documents with different waveforms, so passing one says nothing about the others.

Is IEC 61000-4-25 mandatory?

Not by itself. IEC 61000-4-25 is a test method: it gives immunity test levels, test equipment, set-ups, procedures and reporting for HEMP radiated and conducted disturbances, and IEC states it does not attest conformity. It applies when a contract or specification calls it up. IEC 61000-6-6 (2003), the generic HEMP immunity standard for indoor equipment, bases its test values on the 90 % severity levels of IEC 61000-4-25, and IEC TS 61000-5-10 applies when the customer has decided that protecting critical electronics from HEMP and IEMI matters.

Which edition of IEC 61000-4-25 is current?

The base edition 1.0 is dated 8 November 2001. It has two amendments, AMD1 of 8 March 2012 and AMD2 of 11 December 2019, and IEC sells a consolidated version 1.2 (IEC 61000-4-25:2001+AMD1:2012+AMD2:2019). Quoting it as "2001+A1:2012" misses the 2019 amendment. The IEC catalogue gives a stability date of 2027 for the standard.

What is the RS105 test in MIL-STD-461?

RS105 is the radiated susceptibility test for a transient electromagnetic field. In MIL-STD-461H (17 April 2026) it applies to equipment enclosures exposed to the external electromagnetic environment that have an EMP requirement. The limit is a double exponential with a 50 kV/m peak, a 10 to 90 % rise time between 1.8 and 2.8 ns and a full width at half maximum of 23 ns plus or minus 5 ns. At least five pulses are applied, no more than one per minute. RS105 tests the enclosure only; cable coupling is controlled by CS116.

What does IEC 61000-4-36 cover?

IEC 61000-4-36 gives methods to determine test levels for the immunity of equipment and systems to IEMI sources. The current edition 2.0 is dated 23 March 2020 and replaced the 2014 first edition. It is not limited to narrow-band microwaves: it has generic hyperband, mesoband and hypoband radiated test parameters, conducted parameters, and test methods that include IEMI simulators, reverberation chambers, complex waveform injection, damped sinusoidal injection, ESD, EFT and antenna port injection. Edition 2 added a hyperband and mesoband radiated transient test method (Annex H).

Do HEMP protective devices get qualified to IEC 61000-5-5?

No. IEC 61000-5-5 (1996) defines how protective devices for HEMP conducted disturbance shall be specified, and says that performance requirements are to be given in future IEC documents. The test methods for these devices are in IEC 61000-4-24 (edition 2.0 of 2015, amendment 1 of 2023), which covers gas discharge tubes, varistors and two-port devices such as HEMP filters, including residual voltage or current and peak rate of rise.

What is pulsed current injection (PCI)?

PCI is the MIL-STD-188-125 test of the main barrier protective device at each electrical point of entry. In the public 1998 text of MIL-STD-188-125-1, an inter-site commercial power line takes a short pulse of 5,000 A common mode or 2,500 A wire to ground (rise time 20 ns or less, 500 to 550 ns FWHM), an intermediate pulse of 250 A and a long pulse of 1,000 A, and the residual internal stress for the short pulse on a commercial power feeder must not exceed 10 A. Revision A of 1 July 2021 is a controlled-distribution document, so check the contract edition.

How do HEMP and geomagnetic disturbances relate?

Executive Order 13865 defines both as electromagnetic pulses: HEMP is human-made, a geomagnetic disturbance is natural and driven by solar eruptions, and both can affect large geographic areas. For the North American bulk power system, NERC TPL-007-4 requires benchmark and supplemental GMD vulnerability assessments, a thermal impact assessment of applicable transformers where the effective GIC is 75 A per phase or more, and corrective action plans. TPL-007 addresses GMD, not HEMP.

HEMP and IEMI: IEC 61000-4-25 and hardened electronics

Hugues Orgitello updated 7 Oct 2026 16 min read

HEMP (high-altitude electromagnetic pulse) and IEMI (intentional electromagnetic interference) sit outside ordinary EMC product testing. On the civil side, the documents come from IEC subcommittee SC 77C, High power transient phenomena: environment descriptions (IEC 61000-2-9, 2-10, 2-11, 2-13), test methods (IEC 61000-4-25 for HEMP immunity, IEC 61000-4-36 for IEMI, IEC 61000-4-23 and 4-24 for protective devices) and installation guidance (IEC TR 61000-5-3, IEC TS 61000-5-10). On the military side, MIL-STD-188-125-1 and -2 set HEMP protection for ground-based facilities and transportable systems, and MIL-STD-461 RS105 tests equipment enclosures against the transient field. Several of these texts changed recently: IEC 61000-2-9 has a second edition dated 14 May 2025, IEC 61000-4-23 received an amendment on 25 July 2025, MIL-STD-188-125-1 moved to Revision A on 1 July 2021 (validated again on 31 August 2026) and MIL-STD-461H is dated 17 April 2026. This page gives the current editions with their dates, the numbers that the public texts actually state, and the common readings that those texts contradict.

The threat, in the words of the texts

HEMP. Executive Order 13865 (signed 26 March 2019, 84 FR 12041) defines a high-altitude EMP as a human-made EMP that occurs when a nuclear device is detonated at approximately 40 km or more above the surface of the Earth, and a geomagnetic disturbance (GMD) as a natural EMP driven by a temporary disturbance of the Earth magnetic field resulting from solar eruptions. It adds that both can affect large geographic areas. IEC TS 61000-5-8 gives the scale: a burst at a typical altitude of 100 km illuminates the Earth to a ground radius of 1,100 km, so a distributed network sees the disturbance everywhere at once.

IEC 61000-2-9 describes the radiated HEMP environment and IEC 61000-2-10 the conducted one. IEC 61000-2-11 classifies early-time, intermediate-time and late-time HEMP environments and gives principles for selecting immunity levels. The 2025 edition of IEC 61000-2-9 adds new information on how the early-time HEMP varies over the Earth surface and on the late-time HEMP, plus an informative Annex A on how the standard waveforms were derived and on the advantages and disadvantages of the double exponential waveform.

IEMI and HPEM. IEC 61000-2-13 defines high-power electromagnetic (HPEM) environments for civil facilities, with "high power" starting where the peak electric field exceeds 100 V/m (26.5 W/m² plane-wave power density). IEC 61000-4-36 deals with IEMI, meaning a source operated deliberately against a target. Its generic radiated test parameters are grouped by spectrum: hyperband, mesoband and hypoband (narrow band).

Lightning surge. The IEC 61000-4-5 surge test and the fast transient burst test are covered in surge and burst, IEC 61000-4-5 and 61000-4-4. IEC TR 61000-5-3 includes a comparison of HEMP and lightning protection requirements, to show where they can be combined and where existing lightning protection leaves HEMP consequences uncovered.

The SC 77C family, dated

Every row comes from the IEC catalogue record of the publication (checked 7 October 2026). All of them are maintained by TC 77/SC 77C and carry a stability date of 2027.

Document	Current edition and date	What it does
IEC 61000-2-9	Edition 2.0, 14 May 2025 (replaces edition 1, 19 February 1996)	HEMP environment, radiated disturbance
IEC 61000-2-10	Edition 2.0, 18 November 2021 (replaces the 1998 edition)	HEMP environment, conducted disturbance; new Annex E on the response of simple linear antennas
IEC 61000-2-11	Edition 1.0, 29 October 1999	Classification of HEMP environments, selection of immunity levels
IEC 61000-2-13	Edition 1.0, 9 March 2005	HPEM environments, radiated and conducted
IEC 61000-4-23	Edition 2.0, 20 October 2016, AMD1 25 July 2025	Test methods for protective devices against HEMP and other radiated disturbances (shielding elements)
IEC 61000-4-24	Edition 2.0, 5 November 2015, AMD1 23 August 2023	Test methods for protective devices against HEMP conducted disturbance
IEC 61000-4-25	Edition 1.0, 8 November 2001, AMD1 8 March 2012, AMD2 11 December 2019	HEMP immunity test methods for equipment and systems
IEC 61000-4-33	Edition 1.0, 27 September 2005	Measurement methods for high-power transient parameters
IEC 61000-4-36	Edition 2.0, 23 March 2020 (replaces the 2014 edition)	IEMI immunity test methods for equipment and systems
IEC TR 61000-4-32	30 October 2002	HEMP simulator compendium (datasheets of 42 simulators in 14 countries)
IEC TR 61000-4-35	23 July 2009	HPEM simulator compendium (radiated fields above 500 V/m)
IEC 61000-5-3	IEC TR, 9 July 1999	HEMP protection concepts for civil facilities
IEC 61000-5-5	7 February 1996	How to specify protective devices for HEMP conducted disturbance
IEC 61000-5-6	Edition 1.0, 5 April 2024 (replaces IEC TR 61000-5-6:2002)	Mitigation of external EM influences, now including IEMI
IEC TS 61000-5-8	31 August 2009	HEMP protection methods for the distributed infrastructure
IEC TS 61000-5-9	8 July 2009	System-level susceptibility assessments for HEMP and HPEM
IEC TS 61000-5-10	18 May 2017	Guidance on protecting facilities against HEMP and IEMI
IEC 61000-6-6	Edition 1.0, 9 April 2003	Generic standard, HEMP immunity for indoor equipment

What IEC 61000-4-25 contains

The scope covers immunity test levels and test methods for electrical and electronic equipment and systems exposed to HEMP, for radiated and conducted disturbances. For radiated tests it specifies both small test facilities and large HEMP simulators. It covers laboratory tests and also on-site verification tests on installed equipment, which use the same specifications except for climatic conditions. The table follows the clause structure of the 2001 text.

Clause	Content
5.3 and 5.4.1	Immunity test levels; radiated test levels (Table 1)
5.4.3 to 5.4.5	Small radiated test facilities, large HEMP simulators, frequency-domain spectrum requirements
5.5.1	Conducted test levels: early-time (Table 2), intermediate-time (Table 3), late-time (Tables 4 and 5)
6 and 7	Test generators, instrumentation and set-ups for radiated and conducted tests
8	Test procedure: climatic conditions, test level and exposures, execution
9	Test results and test report
Annex A (informative)	Rationale for the test levels, including example early-time levels for various applications
Annex B (informative)	Conducted immunity tests for antennas
Annex C (informative)	Conducted tests with EC10 and EC11 fast transient generators and the LC slow pulse
Annex D (normative)	Damped oscillatory wave test, with references to ISO 7137, a VG current injection test and MIL-STD-461E

IEC 61000-6-6 turns this into product requirements for indoor equipment connected to low-voltage power (1 kV or less), telecom lines or external antennas. Its test values are based on the 90 % severity levels of IEC 61000-4-25; it assumes gas-tube protectors where telecom lines enter the building and sizes signal-port levels for 10 m of internal cable, with a procedure for longer cables. It has three performance criteria (A normal performance, B temporary self-recoverable degradation, C recoverable degradation) and port-by-port tables (enclosure, signal, external antenna, telecom, DC power, AC power, functional earth).

Protective devices: specify with 5-5, test with 4-23 and 4-24

IEC 61000-5-5 defines how protective devices for HEMP conducted disturbance on signal and low-voltage power lines (up to 1 kV AC) are to be specified, and states that performance requirements are to be given in future IEC documents. IEC TS 61000-5-4 does the same for devices against the radiated field. The test methods are elsewhere:

IEC 61000-4-24 tests conducted-disturbance devices: two-terminal elements such as gas discharge tubes and varistors, and two-port devices such as HEMP combination filters. It covers voltage breakdown and limiting, residual voltage or current, and the peak rate of rise for very fast changes.
IEC 61000-4-23 tests shielding elements against HEMP and other radiated disturbances. Edition 2 (2016) added methods for facilities that only have about 1 m or less of space outside the electromagnetic barrier, because the edition 1 method needed a transmitting antenna farther outside.
IEC 61000-4-33 gives the measurement methods for the transient responses (fields, current, voltage, charge) and the parameters used to describe them: peak, rise time, pulse width and waveform norms.

Military texts: MIL-STD-188-125 and RS105

Reference	Edition status	Scope
MIL-STD-188-125-1	Base 17 July 1998 (superseding MIL-STD-188-125A of 15 February 1994), Notice 1 validation 7 April 2005, Revision A 1 July 2021, Notice 1 administrative 26 July 2021, Notice 2 validation 31 August 2026; Revision A is a controlled-distribution document	HEMP protection for fixed ground-based facilities performing critical, time-urgent missions
MIL-STD-188-125-2	3 March 1999; cited as Part II by DI-NUSU-82340, itself validated on 31 August 2026	Same, for transportable systems
MIL-STD-461H RS105	17 April 2026 (supersedes MIL-STD-461G of 11 December 2015)	Transient electromagnetic field on equipment enclosures

The 1998 text of MIL-STD-188-125-1 carries Distribution Statement A. Its main requirements:

The facility HEMP shield, with all point-of-entry (POE) protective devices installed, must meet the minimum shielding effectiveness curve of its Figure 1, measured with the Appendix A procedures. Shield acceptance testing is repeated in the affected area when points of entry are added or the shield is breached and repaired.
Personnel entries use a two-door shielded waveguide-below-cutoff entryway or a two-door shielded vestibule.
Piping and ventilation points of entry are waveguides below cutoff (WBC) with a cutoff frequency of at least 1.5 GHz and enough length for at least 80 dB attenuation at 1 GHz; no conductor may pass through a ventilation WBC.
Every penetrating power, communications or control conductor gets a main barrier protective device, verified by pulsed current injection (PCI). Standard voice and data lines are converted to fibre optics outside the barrier and enter on all-dielectric cable through a WBC; the optoelectronic equipment left outside gets special protective measures when the line is mission critical.
A built-in capability to monitor shield leakage is required, and the facility is subject to hardness maintenance and hardness surveillance, with reverification tests at intervals set in the technical manual.

PCI levels from Table I of the 1998 text, for the classes that receive all three pulses:

Class of POE (1998 text)	Pulse	Peak short-circuit current	Rise time	FWHM
Commercial power, inter-site	Short	5,000 A common mode, 2,500 A wire to ground	20 ns or less	500 to 550 ns
Commercial power, inter-site	Intermediate	250 A	1.5 µs or less	3 to 5 ms
Commercial power, inter-site	Long	1,000 A	0.2 s or less	20 to 25 s
Audio and data, inter-site	Short	5,000 A common mode, 5,000 A or 500 A wire to ground	20 ns or less	500 to 550 ns
Audio and data, inter-site	Intermediate and long	250 A and 1,000 A	1.5 µs and 0.2 s or less	3 to 5 ms and 20 to 25 s

For a commercial power feeder, the short pulse injected through a source impedance of at least 60 Ω must leave a residual internal stress of no more than 10 A, and the intermediate and long pulses must cause no damage or degradation. For several signal and antenna classes the residual limit is 0.1 A or 1 A. These numbers are from the 1998 edition; a contract that cites Revision A takes its numbers from that controlled document.

RS105 in MIL-STD-461H applies to equipment and subsystem enclosures exposed to the external electromagnetic environment that have an EMP requirement (461G did not include the EMP condition). The limit waveform is a double exponential with a 50 kV/m peak; the tolerances are a 10 to 90 % rise time between 1.8 and 2.8 ns, a FWHM of 23 ns ± 5 ns, and a peak between 0 and 6 dB above the limit at each of five grid points. At least five pulses are applied, no more than one per minute, starting at 10 % of the level. The test uses a TEM cell or parallel plate line, and the largest EUT dimension should be no more than a third of the plate separation. Appendix A states that RS105 applies only to enclosures and that cable coupling is controlled by CS116. More on MIL-STD-461 in MIL-STD-461H and MIL-STD-464D.

Civil critical infrastructure

United States. Executive Order 13865 assigns tasks rather than test levels. Among them, the Secretary of Energy had to review existing EMP standards within one year and develop or update quantitative benchmarks describing EMP waveform and intensity for infrastructure owners and operators. The Secretary of Defense had to run a pilot test of hardening approaches for a strategic military installation and review EMP-related standards for Department of Defense systems. For the bulk power system, NERC TPL-007-4 covers GMD, not HEMP. It applies to facilities with transformers that have a high-side wye-grounded winding above 200 kV, and requires a benchmark GMD vulnerability assessment at least once every 60 calendar months, supplemental assessments, a thermal impact assessment of transformers where the effective GIC reaches 75 A per phase, and corrective action plans.

Facilities in general. IEC TS 61000-5-10 is written for commercial facilities, existing or new, once the customer has decided that protecting critical electronics from HEMP and IEMI matters. It works from the whole body of SC 77C documents and covers HEMP and IEMI environment levels, protection and testing approaches for new and for existing buildings, and hardness maintenance, including general annual maintenance and maintenance of point-of-entry filters and metal oxide varistors. IEC 61000-5-6:2024 now covers IEMI alongside lightning, RF transmitters and HEMP.

European Union. None of the SC 77C documents is a product regulation. Whether one applies to an EU project follows from the procurement specification or the operator requirements, not from the EMC Directive test route.

Protection techniques

The IEC TR 61000-5-3 and MIL-STD-188-125-1 approach is layered: a continuous shield, treatment of every penetration, grounding to the shield, then hardening of equipment that remains exposed.

Shield. MIL-STD-188-125-1 requires a continuous conductive enclosure, normally steel or copper, electromagnetically closed at all seams and joints. The shield performance is measured with all POE devices installed, because the penetrations set the result. For shielding fundamentals see shielding theory for EMC.
Penetrations. Conductors get a main barrier device; pipes and ducts get WBC sections; standard voice and data lines go to fibre. A conductor run through a ventilation WBC is forbidden in the 1998 text.
Grounding. MIL-STD-188-125-1 uses the equipotential ground plane method, with the facility HEMP shield forming a major part of that plane; grounds inside are bonded to the inner surface of the shield, grounds outside to the outer surface or the earth electrode. See grounding for EMC.
Protective devices. Specify them per IEC 61000-5-5, test them per IEC 61000-4-24 or the PCI procedure the contract cites.
Maintenance. Both IEC TS 61000-5-10 (clause 9) and MIL-STD-188-125-1 (hardness maintenance and surveillance) treat the protection as something that degrades and has to be re-checked.

Test facilities

IEC TR 61000-4-32 (2002) lists HEMP simulators: datasheets on 42 EMP simulators in 14 countries that were operational or could be made available. IEC TR 61000-4-35 (2009) does the same for HPEM simulators, narrow band and wide band, restricted to facilities reaching radiated fields above 500 V/m. Both are dated; check with the facility before planning on them. RS105 itself fits in a laboratory TEM cell or parallel plate line. For chamber types used in ordinary radiated testing see EMC chamber types.

A test sequence for hardened equipment

Get the requirement in writing: which document, which edition (IEC 61000-4-25 with or without AMD2, MIL-STD-188-125-1 base or Revision A, MIL-STD-461G or H), which level and which performance criterion.
Map the ports and penetrations: enclosure, power, signal, antenna, telecom, functional earth (the IEC 61000-6-6 port list is a good checklist).
Specify protective devices per IEC 61000-5-5 and test them per IEC 61000-4-24; test shielding elements per IEC 61000-4-23.
Equipment tests: IEC 61000-4-25 radiated and conducted tests, or RS105 plus CS116 under MIL-STD-461.
Facility tests where MIL-STD-188-125 applies: shielding effectiveness to Appendix A, PCI on every electrical POE, then verification testing.
IEMI where specified: derive the levels with IEC 61000-4-36 and pick the methods it lists (simulator, reverberation chamber, CWI, DSI, ESD, EFT, antenna port injection).
Report with the measured waveform parameters (peak, rise time, width) as described in IEC 61000-4-33, and plan hardness maintenance.

Claims the texts contradict

Claim (including what this page said before)	What the texts say
"IEC 61000-2-9:1996 is the current HEMP environment standard"	Edition 2.0 of 14 May 2025 cancels and replaces the 1996 edition (IEC catalogue)
"IEC 61000-2-10 dates from 1998"	Edition 2.0 of 18 November 2021 replaces it
"IEC 61000-4-25:2001+A1:2012" as the full reference	AMD2 was published on 11 December 2019; the consolidated version is 1.2
"Protective devices are qualified per IEC 61000-5-5"	IEC 61000-5-5 says how to specify them and leaves performance requirements to future documents; the test methods are IEC 61000-4-24
"PCI per IEC 61000-4-25 applies several hundred amperes"	PCI is the MIL-STD-188-125 test; its 1998 Table I short pulse is 5,000 A common mode on power and data lines. IEC 61000-4-25 conducted tests are in clause 5.5 with their own levels
"The E1 reference pulse is 2.5/25 ns"	MIL-STD-461H RS105: rise time 1.8 to 2.8 ns (10 to 90 %), FWHM 23 ns ± 5 ns, peak 50 kV/m
"IEC 61000-4-36 covers narrow-band HPM"	It also covers hyperband and mesoband sources, and edition 2 (2020) added a hyperband and mesoband radiated transient method in Annex H
"MIL-STD-188-125-1 (2005)"	Base document 17 July 1998; 7 April 2005 is a validation notice; Revision A is dated 1 July 2021
"RS105 qualifies the whole equipment, cables included"	RS105 applies to enclosures only; cable coupling is controlled by CS116 (MIL-STD-461H Appendix A)
"HEMP bursts happen at 30 to 400 km"	Executive Order 13865: approximately 40 km or more; IEC TS 61000-5-8 uses a typical 100 km burst with a 1,100 km ground radius
"IEC 61000-5-3 is a standard that fixes protection concepts"	It is a technical report (IEC TR 61000-5-3:1999) giving design and evaluation elements
"NERC TPL-007 covers HEMP"	TPL-007-4 covers geomagnetic disturbances only

Frequent pitfalls

Pitfall	Consequence
Citing an IEC edition without its amendments	Lab and customer test to different texts (IEC 61000-4-25 AMD2, IEC 61000-4-23 AMD1 of 2025, IEC 61000-4-24 AMD1 of 2023)
Using the public 1998 MIL-STD-188-125-1 on a Revision A contract	Numbers may differ; Revision A is controlled distribution and must come from the contracting office
Treating RS105 as the whole HEMP test	Cable coupling (CS116) and facility protection are left untested
A conductor through a ventilation WBC	Forbidden by MIL-STD-188-125-1 (clause 5.5.3): no conductor may pass through the waveguide
Adding a POE after shield acceptance without retest	MIL-STD-188-125-1 requires acceptance testing to be repeated in the affected area
No hardness maintenance plan	Both IEC TS 61000-5-10 and MIL-STD-188-125-1 expect the protection to be maintained and re-checked
Using IEC 61000-4-3 or 4-5 results as HEMP or IEMI evidence	Different documents, waveforms and levels; see the IEC 61000-2-13 threshold of 100 V/m for HPEM

Going further

IEC 61000-4-3, radiated RF immunity: the ordinary radiated immunity test
IEC 61000-4-8, power-frequency magnetic field immunity: low-frequency magnetic immunity
MIL-STD-461 and MIL-STD-464, defence EMC: the 19 test methods including RS105 and CS116
EMC chamber types: chamber typology used for radiated immunity testing
Surge and burst, IEC 61000-4-5 and 61000-4-4: the lightning surge and fast transient tests
Shielding theory for EMC and grounding for EMC
Glossary: definitions of HEMP, IEMI, HPEM, GIC, GMD, SPD, WBC

Frequently asked questions

What is the difference between HEMP, IEMI and a lightning surge?: HEMP is the electromagnetic pulse of a nuclear detonation at high altitude; Executive Order 13865 places it at approximately 40 km or more above the Earth. IEC 61000-2-11 classifies its early-time, intermediate-time and late-time environments, and IEC 61000-2-9 and IEC 61000-2-10 describe the radiated and conducted environments. IEMI is intentional electromagnetic interference from a deliberately operated source, covered by IEC 61000-4-36. A lightning surge is the ordinary IEC 61000-4-5 test. The three are specified in different documents with different waveforms, so passing one says nothing about the others.
Is IEC 61000-4-25 mandatory?: Not by itself. IEC 61000-4-25 is a test method: it gives immunity test levels, test equipment, set-ups, procedures and reporting for HEMP radiated and conducted disturbances, and IEC states it does not attest conformity. It applies when a contract or specification calls it up. IEC 61000-6-6 (2003), the generic HEMP immunity standard for indoor equipment, bases its test values on the 90 % severity levels of IEC 61000-4-25, and IEC TS 61000-5-10 applies when the customer has decided that protecting critical electronics from HEMP and IEMI matters.
Which edition of IEC 61000-4-25 is current?: The base edition 1.0 is dated 8 November 2001. It has two amendments, AMD1 of 8 March 2012 and AMD2 of 11 December 2019, and IEC sells a consolidated version 1.2 (IEC 61000-4-25:2001+AMD1:2012+AMD2:2019). Quoting it as "2001+A1:2012" misses the 2019 amendment. The IEC catalogue gives a stability date of 2027 for the standard.
What is the RS105 test in MIL-STD-461?: RS105 is the radiated susceptibility test for a transient electromagnetic field. In MIL-STD-461H (17 April 2026) it applies to equipment enclosures exposed to the external electromagnetic environment that have an EMP requirement. The limit is a double exponential with a 50 kV/m peak, a 10 to 90 % rise time between 1.8 and 2.8 ns and a full width at half maximum of 23 ns plus or minus 5 ns. At least five pulses are applied, no more than one per minute. RS105 tests the enclosure only; cable coupling is controlled by CS116.
What does IEC 61000-4-36 cover?: IEC 61000-4-36 gives methods to determine test levels for the immunity of equipment and systems to IEMI sources. The current edition 2.0 is dated 23 March 2020 and replaced the 2014 first edition. It is not limited to narrow-band microwaves: it has generic hyperband, mesoband and hypoband radiated test parameters, conducted parameters, and test methods that include IEMI simulators, reverberation chambers, complex waveform injection, damped sinusoidal injection, ESD, EFT and antenna port injection. Edition 2 added a hyperband and mesoband radiated transient test method (Annex H).
Do HEMP protective devices get qualified to IEC 61000-5-5?: No. IEC 61000-5-5 (1996) defines how protective devices for HEMP conducted disturbance shall be specified, and says that performance requirements are to be given in future IEC documents. The test methods for these devices are in IEC 61000-4-24 (edition 2.0 of 2015, amendment 1 of 2023), which covers gas discharge tubes, varistors and two-port devices such as HEMP filters, including residual voltage or current and peak rate of rise.
What is pulsed current injection (PCI)?: PCI is the MIL-STD-188-125 test of the main barrier protective device at each electrical point of entry. In the public 1998 text of MIL-STD-188-125-1, an inter-site commercial power line takes a short pulse of 5,000 A common mode or 2,500 A wire to ground (rise time 20 ns or less, 500 to 550 ns FWHM), an intermediate pulse of 250 A and a long pulse of 1,000 A, and the residual internal stress for the short pulse on a commercial power feeder must not exceed 10 A. Revision A of 1 July 2021 is a controlled-distribution document, so check the contract edition.
How do HEMP and geomagnetic disturbances relate?: Executive Order 13865 defines both as electromagnetic pulses: HEMP is human-made, a geomagnetic disturbance is natural and driven by solar eruptions, and both can affect large geographic areas. For the North American bulk power system, NERC TPL-007-4 requires benchmark and supplemental GMD vulnerability assessments, a thermal impact assessment of applicable transformers where the effective GIC is 75 A per phase or more, and corrective action plans. TPL-007 addresses GMD, not HEMP.