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| Press Release

EPRI Report Suggests Regional Grid Disruptions Resulting From a High-Altitude Electromagnetic Pulse

PALO ALTO, Calif., Dec. 20, 2017 (GLOBE NEWSWIRE) -- New research on the potential risk to the U.S. electric grid from a high-altitude electromagnetic pulse (HEMP) event suggests that service interruption due to a late-time pulse or E3 alone would be limited to a regional level and would not trigger a nationwide grid failure.

The Electric Power Research Institute (EPRI) report focuses on the likely service interruption on the power grid from the detonation of a nuclear weapon high above the earth’s surface. Such an event would release separate electromagnetic pulses that could disrupt the flow of electricity without the widespread physical destruction and radioactive fallout from ground-targeted nuclear attacks.

Three types of electromagnetic pulses that could impact the electric grid are a high-magnitude, short duration pulse (E1); an intermediate pulse similar to lightning (E2); and a late-time component (E3), which is similar to a severe geomagnetic disturbance event. This most recent report evaluated the effects of the E3 pulse.

EPRI conducted 11 different simulations of a HEMP event across the United States. Five of the simulations would have triggered a regional power failure potentially affecting several states. Two would have led to more localized failures.

The report also identified steps that could potentially limit the impact of an E3 during a HEMP event. Such steps include installing technologies to reduce or block the flow of geomagnetically-induced currents (GICs) or adding controls to automatically disconnect power system loads during the event.

The EPRI report, Magnetohydrodynamic Electromagnetic Pulse (MHD-EMP) Assessment of the Continental U.S. Electric Grid: Voltage Stability Analysis (, called for further study to determine the combined effects of E1, E2 and E3 on the power grid.

“This report is another step in providing the technical basis that is needed before an effective strategy to mitigate the effects of a HEMP can be developed,” said EPRI President and CEO Michael W. Howard. “We will continue on this path as we identify and test cost-effective measures to reduce grid vulnerability to a HEMP event.”

The report released today was the second of two major EPRI studies on the potential impact of E3 from a HEMP event. The first report (, released in February, focused on the potential for thermal damage on bulk power transformers as a result of a single HEMP event. It concluded that three to fourteen of the transformers would be at risk of thermal damage.

The E3 simulations assumed an event involving a 1.4 megaton bomb detonated 400 kilometers (roughly 250 miles) above the earth. A 1.4 megaton bomb would have the explosive power of 1.4 million tons of dynamite, nearly 100 times more than the nuclear bomb dropped on Hiroshima. The electromagnetic pulse used in this study is based on data from an atmospheric test conducted by the U.S. government in 1962 (Starfish Prime).

“Taken together, the two EPRI studies have significantly increased our understanding of the impact of an E3 pulse on the electric grid. Although the results should help allay our worst fears, we still have a lot to learn,” said Rob Manning, vice president of Transmission and Distribution at EPRI. “It’s important that we build on these analyses by identifying and testing ways to limit impacts of these pulses to all of the grid’s major components and systems.”

The latest E3 assessment also indicated that that the scale of the resulting power outage caused solely by an E3 pulse would be consistent with previous wide-scale events, but recovery times could be affected by damage to critical electronics and other equipment and systems caused by E1 or E2 pulses triggered by the same HEMP event. Future EPRI studies will examine those issues.

EPRI research continues in partnership with National Labs and the Department of Energy to identify the potential impacts of high-altitude electromagnetic pulse on bulk power system and develop cost-effective options for mitigating the potential impacts. EPRI research in 2018 will focus on:


  • Modeling the effects of E1 and E2 on electric infrastructure and developing the capability to simulate the combined effects of E1, E2 and E3
  • Developing additional unclassified E1 and E3 scenarios and modeling capability that can be used to perform bulk-power system assessments
  • Testing the resilience of intelligent electronic devices in a HEMP event
  • Research and development of cost-effective ways to limit the impacts of a HEMP

About EPRI:
The Electric Power Research Institute, Inc. (EPRI, conducts research and development relating to the generation, delivery and use of electricity for the benefit of the public. An independent, nonprofit organization, EPRI brings together its scientists and engineers as well as experts from academia and industry to help address challenges in electricity, including reliability, efficiency, affordability, health, safety and the environment. EPRI's members represent approximately 90 percent of the electricity generated and delivered in the United States, and international participation extends to more than 30 countries. EPRI's principal offices and laboratories are located in Palo Alto, Calif.; Charlotte, N.Car.; Knoxville, Tenn.; and Lenox, Mass.


A photo accompanying this announcement is available at

Clay Perry
Electric Power Research Institute

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