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Protecting Industry from HEMP and IEMI

Applying the IEC SC 77C Standards

This article is intended to inform readers of the situation today with regard to the ability of the EMC experts and suppliers to protect modern electronic systems, especially those which control the critical infrastructures (power, communications, financial system, water delivery, etc.) from the threat of the high-altitude electromagnetic pulse (HEMP) and the more recent threat of electromagnetic weapons that can create intentional electromagnetic interference (IEMI).

This article will review the early history of HEMP and the more recent history of electromagnetic weapons that can create IEMI. Also, we will discuss the work of the U.S. Congressional EMP Commission due to its strong contributions in raising the public awareness of the HEMP threat and the need to protect critical infrastructure systems.

In addition, the work of Subcommittee 77C of the International Electrotechnical Commission (IEC) has produced over the past 29 years a set of basic standards and publications dealing with HEMP and IEMI that provide the tools to protect nearly any electronic system from these severe electromagnetic (EM) threats.

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With the use of these IEC standards and a more limited set of IEEE, CIGRE, and ITU-T publications, several important industries have started to protect their facilities from attack. In addition IEC SC 77C is continually improving its standards to ensure they can be applied in the most efficient manner.

Finally the IEC has produced an overarching document addressing the protection of fixed facilities that allows a great deal of flexibility in the approaches that may be used. This should provide a low-cost path for protection for many different cases.

History of HEMP and IEMI

As with many technologies, surprises often occur when testing is performed. The United States and the former Union of Soviet Socialist Republics (USSR) performed high altitude nuclear device testing in space in 1958 and 1962 to evaluate the effects that might occur. The U.S. tested in the tropics of the North Pacific region, while the Soviets mainly tested over land (Kazakhstan). While many details of these tests are still classified, some information has been made publicly available in recent years.

For example, the U.S. Starfish test was performed in July 1962 over Johnston Island in the North Pacific (1.4 MT at an altitude of 400 km) as shown in Figure 1. The test was not performed to evaluate the electromagnetic pulse (EMP), although a few measurements were fielded as scientists such as Enrico Fermi and Hans Bethe had anticipated that EMP signals would occur. The Hawaiian Islands were the nearest location of population (~1400 km away), and there were some notable effects including the immediate loss of some streetlights (the test was at 11 pm, local time in Hawaii). Other HEMP interference effects were noted by scientists, but all of these effects have not been released to the American public. It is notable that the Congressional EMP Commission has asked the U.S. Department of Defense to release this information, as some “experts” claim that no real effects were actually experienced. So far, this request has not been satisfactorily answered.

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Figure 1: Overview of effects published from the U.S. Starfish high altitude nuclear test in July 1962 [1]

In October 1962, Soviet researchers performed three high altitude tests over Kazakhstan (300 kT at burst heights of 300, 150 and 60 km) in order to evaluate the effectiveness of their nuclear anti-ballistic missile system. These researchers were also surprised to observe many HEMP impacts on nearby power and communications infrastructures, which were not intended to be part of their tests (
Figure 2). However, because the tests were conducted over land, they exposed long power and communications lines to the E1, E2 and E3 portions of the HEMP, and many systems were impacted. In June 1994, Russian scientists presented and published papers summarizing the HEMP effects that were noted in 1962. They also admitted that they were surprised at the extent of the effects, and appointed a special committee headed by Dr. Andrei Sakharov to determine how to protect against the HEMP.

Figure 2: Effects noted during Soviet high-altitude nuclear tests in October 1962. Chart is from [2] and notations are by W. Radasky, who attended the presentation of this chart in June 1994 [3].

Based on the information obtained through testing by both the U.S. and the Soviet Union in 1962, it was recognized that HEMP could affect the electronics of that time. Also, with some direct measurements of the HEMP signals, both the U.S. and the Soviet Union built large physical simulators to generate the early-time HEMP (the first microsecond known today as the E1 HEMP, as shown in Figure 3). These simulators and those built by other countries over the years are documented in IEC 61000-4-32. The reason that these simulators are important is that over many decades new electronics were tested, and a consistent trend was observed that, without adequate protection, digital electronics are more vulnerable to HEMP than older analog systems.

Figure 3: Graphical description of three analytic functions that describe the early-time (E1), intermediate-time (E2) and late-time (E3) HEMP as described in [4]

While the early work in the U.S. and the Soviet Union was focused on protecting military systems (such as strategic missile systems) and critical communications systems (see for example MIL-STD-188-125-1 [5]), today the concern is focused mainly on commercial systems. This is because commercial companies normally cannot afford to place all of their electronics in highly-shielded buildings as prescribed by the U.S. military.

It is in this context that the U.S. Congressional EMP Commission under the chairmanship of Dr. William Graham began work in 2001, which extended to 2008. Several public reports were written which recommended that the government encourage the protection of critical infrastructure systems, with emphasis on the power system, which was referred to as the “Keystone.”

In 2017, a brief one-year review was performed again by the U.S. Congressional EMP Commission to review the response to their previous recommendations. Unfortunately, the Commission found that little progress had been made in implementing the recommendations made back in 2008, as detailed in the most recently published Commission reports (

Although the threat of HEMP is significant due to the high levels of fields in both the time and frequency domains covering continental areas in a near simultaneous exposure, a new threat, IEMI, has now emerged that has similar features to the E1 HEMP, as shown in Figure 4. Beginning in 1999, the EM technical community became aware of the ability of high-power, solid-state devices to produce very fast rising voltage pulses (as fast as 100 ps), which when matched to a specially designed antenna can produce very high peak transient electromagnetic fields. From extensive testing of these devices and the evaluation of their effects on commercial electronics, it is clear that IEMI can easily upset and damage electronics. There have already been criminal attacks against video cameras and GPS systems that have employed IEMI. But, unlike HEMP, the maximum operable distances for this threat are typically less than 100 meters as described in Figure 5 (except for jammers that can be effective over many kilometers).

Figure 4: The relationship of IEMI electromagnetic fields in the frequency domain to the E1 HEMP and an example of nearby lightning EMP fields from a cloud to ground strike [6]


Figure 5: A typical scenario for an EM weapon to produce IEMI inside of a building with electronic systems [7]

The reason to consider both of these threats together is that the methods for protecting against them share significant commonalities.

IEC Standards for HEMP and IEMI Protection

The effort to standardize the protection of commercial electronics from the effects of HEMP began in 1989 as a working group under IEC TC 77 (EMC). Mr. Manual Wik of Sweden was the convenor of this working group, and he recruited this writer to work with the IEC in the subsequent years. In 1992, we were able to convince the management of IEC TC 77 that the work deserved its own subcommittee, and IEC SC 77C was formed in May of that year. It is also noteworthy that IEC SC 77C added IEMI to its scope of its work in 1999, thereby requiring more emphasis on transients with frequency content above 1 GHz.

It is interesting to note that as the Cold War ended there was still strong interest in developing protection standards for HEMP in Europe. Several IEC projects were identified to provide background into the threat and to produce simple radiated and conducted environment standards based on open publications (IEC 61000-2-9 and IEC 61000-2-10). It should be noted that the decision was made at the beginning to publish all of the standards related to high power transient phenomena in the IEC 61000 series, as it was clear that HEMP and IEMI were parts of the EMC problem.

It is also interesting that over the years the protection methods required involved shielding for the EM fields and filters/surge arresters for conducted transients. These protection methods already existed, but sometimes needed only some minor work to tailor them to the new threats. At the same time, due to the trend of higher frequency communications systems and an increased understanding of electrostatic discharge (ESD) transients, there was more emphasis in the general field of EMC on the protection of equipment for frequencies higher than 1 GHz.

At the present time, the list of IEC SC 77C publications is extensive and is shown below. While most of these standards are basic standards (covering some basic aspect of the environment or test methods) the newest document (IEC 61000-5-10) describes methods for using the entire group of standards to protect modern systems inside of ground-based facilities. This publication will be discussed in more detail later in this article.

Industry Efforts to Protect Against HEMP and IEMI

Over the past 10 years there have been efforts, led chiefly by the power industry, to assess and to protect critical infrastructure facilities and systems against HEMP and/or IEMI. While some companies have done more than others, here is a general list of the efforts that have been undertaken:

  • HEMP/IEMI assessments of existing power substation buildings and electronics
  • HEMP/IEMI assessments of existing power control centers and their electronics
  • HEMP/GMD assessments of high voltage power grids and their high voltage transformers
  • HEMP/IEMI protection of new power control centers
  • HEMP/IEMI protection of new substation buildings and electronics
  • HEMP/IEMI prototype protection methods for existing power substation buildings
  • HEMP/IEMI protection methods for substation yard cables leading to critical electronics

Importantly, new facilities that have included provisions for EM protection during their initial design and construction have been shown to have low relative costs, especially for power control centers. The hardening of new substation buildings is more complex due to the many external cables entering these buildings, but some new approaches hold promise. There is even some progress in hardening existing substation electronics.

However, for these efforts to be successful, it is important to make public the time required to accomplish the hardening and the costs to do so after the projects are completed. This process would also be facilitated by industry-wide encouragement.

Of course, the largest challenge in hardening any facility is the cost. It appears that new construction is the best way to achieve hardness as metal walls can be integrated into the structure. Often, metallic shielded walls can reduce some of the costs of the normal wall construction, thereby providing a reduction of the incremental cost. Retrofit hardening is more difficult, but there are approaches to provide partial protection, which can be cheaper, and will protect against levels of the HEMP/IEMI that are not worst case.

Another challenge is that there are many power companies and other owners of the critical infrastructures that believe that the U.S. Government should work to ensure that a nuclear detonation producing HEMP does not occur over the U.S. Whether this can be achieved by an upgraded ABM system and/or pre-emptive methods to prevent a missile launch should be considered. On the other hand, the threat of IEMI is very similar to a physical attack (such as a rifle attack), which requires the attacker to be close to their target (the EM weapon fields fall off rapidly with distance). In this case, some power companies are considering higher external walls in power substations which can serve to partially attenuate the EM fields.

Future Efforts

The IEC is listening to those who are active in hardening critical infrastructure facilities and systems, and plans to continue to update the existing HEMP/IEMI standards in SC 77C to be more useful to industry.

One of the newest IEC publications is IEC/TS 61000-5-10 Ed. 1.0 (2017-05-18): Electromagnetic compatibility (EMC) – Part 5-10: Installation and mitigation guidelines – Guidance on the protection of facilities against HEMP and IEMI. This document considers the protection of any new or existing facility and, through the use of the other basic standards, develops alternate approaches for increasing the protection level of facilities. The publication has a number of annexes that summarize each of the IEC SC 77C standards in the series published to date. It also considers the mission of the facility to determine what level of protection is needed.

We believe that as IEC 61000-5-10 is applied in different projects, expertise to protect against HEMP/IEMI will increase and that cost-effective protection methods will become obvious, perhaps even for classes of facilities with similar functions. Those of us working in this area of protection hope that those performing this important work will publish the results of their efforts for the benefits of others. In addition, those of us who are active through our work on IEC National Committees encourage other EMC engineers and companies that produce protection hardware to join in that effort.


This article has briefly reviewed the threats of HEMP and IEMI as observed in 1962 for HEMP and in 1999 for IEMI (recognition of the importance of IEMI was widely acknowledged in 1999). In both cases, experimental evidence was (and is today) important in understanding the risk and the need to protect our critical infrastructures.

Since 1989, the IEC has been working tirelessly to develop publications that explain the threat, how to test equipment to the threat, and how to protect equipment by employing various methods. Specifically, this means reducing the HEMP/IEMI environments present at the location of the equipment through the use of building, room or rack EM shielding, and through cable transient protection.

Industry has already made some efforts to protect facilities from these threats for both new construction and for improving existing facilities with electronics. It is hoped that these successful hardening programs can be documented and published to help various critical industries find the optimum approaches for hardening in the future.

In 2017 the IEC produce IEC 61000-5-10 which consolidates all of its previous work to provide alternative approaches for industry to protect and to test equipment and systems for susceptibility to the threats of HEMP/IEMI. It is hoped that this new document will make an important contribution to our understanding of the threat, and how best to protect our critical infrastructures in the future.


  1. William Graham, Chairman of the U.S. Congressional EMP Commission, “Commission to Assess the Threat from High Altitude Electromagnetic Pulse (EMP): Overview,” Presentation to the U.S. Congress in July 2004.
  2. Vladimir Loborev, “Up to Date State of the NEMP Problems and Topical Research Directions,” Presentation at the EUROEM 94 International Symposium, Bordeaux, France, 30 May – 3 June 1994. Also published in Electromagnetic Environments and Consequences, Part I, edited by D.J. Serafin, et al., p. 15.
  3. William Radasky, “Notations on the HEMP chart presented by V. Loborev in reference [2], based on his words (as translated during the presentation),” Metatech Corporation, 1 June 1994.
  4. Kenneth Smith, “Plot of analytic formulas selected by the IEC to describe the three phases of the high altitude electromagnetic pulse,” Metatech Corporation, April 1992.
  5. MIL-STD-188-125-1, “High-Altitude Electromagnetic Pulse (HEMP) Protection for Ground-Based C4I Facilities Performing Critical, Time-Urgent Missions, Part 1: Fixed Facilities, 7 April 2005.
  6. Richard Hoad, “Frequency domain comparison of IEMI with other transient waveforms,” Personal Communications, November 2016.
  7. Michael Messier, “One scenario to create IEMI effects on the electronics inside a building,” Metatech Corporation, 8 February 1999.

William A. Radasky, Ph.D., P.E.,
has worked in the field of high power transient phenomena for more than 50 years and has published over 500 reports, papers and articles during his career dealing with transient electromagnetic environments, effects and protection. He was awarded the Lord Kelvin Medal by the IEC in 2004, the Carl E. Baum Medal in 2017, and is an IEEE Life Fellow. He founded Metatech Corporation in 1984 and is the President and Managing Engineer. He can be reached at

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