A “Deliberate Approach” to Electromagnetic Pulses

New EPRI Research Outlines Possible Impacts and How to Protect Against Them

By Chris Warren

An EPRI study has found that a high-altitude electromagnetic pulse (HEMP) is unlikely to cause nationwide and long-lasting blackouts as a result of damage to critical substation assets, though the potential exists for substantial disruption of transmission systems. The study also highlighted steps that can be taken to protect grid assets against the worst impacts of HEMPs. Additional research and investigation are needed to understand potential HEMP impacts on power plants, distribution systems, renewable energy systems, and other parts of the grid—as well as other critical infrastructure sectors that support grid operations such as natural gas, water, and telecommunications.

Building on earlier work, the report provides analysis of potential transmission grid impacts and cost-effective mitigations. (It does not examine impacts on generation, distribution, and end-use loads.) EPRI worked closely with HEMP experts at the U.S. Department of Energy, the Defense Threat Reduction Agency, and the Lawrence Livermore, Sandia, and Los Alamos national laboratories.

Researchers modeled the voltage surges that digital protective relays can be exposed to as a result of E1 pulses. A detonation 125 miles above the earth’s surface can generate an E1 pulse spanning an area of approximately three million square miles. However, impacts diminish with distance from the ground zero location and can vary depending on the location of the electronics.

“We modeled these electric fields and incorporated them into a power grid model to assess equipment exposure to voltage and current surges,” said EPRI Senior Program Manager Randy Horton, who oversees HEMP research.

Through laboratory testing, EPRI measured the effects of E1 pulses on equipment such as digital protective relays. In one set of tests, researchers simulated E1 pulses directly hitting equipment and recorded when the equipment was damaged or disrupted. In a second set of “direct injection” tests mimicking voltage and current surges in the cables feeding into equipment, researchers recorded the levels of E1-induced surges that caused damage or disruption.

“The modeling told us what the equipment could be exposed to during an event while the lab testing told us the exposure levels that the equipment could withstand,” said Horton. “By evaluating these two sets of results, we were able to determine if damage or disruption could occur.”

Results indicated that E1 pulses have the potential to damage digital protective relays spanning an area as large as an entire electrical interconnection. The severity and extent of damage depends on the location of the equipment and the strength of the electric field produced by a HEMP. Some equipment may fail completely, while other components may be disrupted or unaffected. E1-related damage to digital relays and other controls could hamper recovery efforts and long-term grid operations. E1 pulses are unlikely to cause an immediate, interconnection-wide blackout, though more research is needed to gauge how damaged digital relays could affect power system stability.

Assessment of E2 impacts indicated that damage to the transmission system is not expected to occur. Assessment of E3 impacts indicated that a regional blackout (multiple states) is possible, but immediate, widespread transformer damage is not expected to occur.

Other findings:

• A moderately powerful E1 pulse could disrupt or damage approximately 5% of digital protective relays in the transmission line terminals of an interconnection while a more severe E1 could disrupt or damage about 15%.
• Viable options to mitigate E1-related damage include shielded cables with proper grounding; low-voltage surge protection devices and filters; grounding and bonding enhancements; and reserve supplies of digital protective relays and communication equipment.
• Viable protections against E3-related damage are similar to protections against geomagnetic disturbances and include keeping replacement transformers on hand and blocking or reducing the flow of geomagnetically induced currents.

“Overall, we found that a HEMP’s potential impacts on the transmission system are real and of concern, and they can be mitigated by several approaches that are outlined in our report,” said Horton. “Our findings do not support the belief that HEMPs can cause nationwide blackouts lasting for years.”

In 2016, EPRI launched research on HEMPs to investigate concerns that a HEMP attack could result in long-term blackouts. It aims to provide utilities, regulators, and policymakers with a technical basis for assessing the potential impacts and for making decisions about mitigation options.

At the time, some stakeholders advocated that utilities deploy measures that the U.S. military uses to protect electronics in key facilities from a HEMP attack. “Those measures were never designed to be used in a substation and are very costly,” said Horton. “Before regulators and policymakers required utilities to follow those military standards, power companies wanted to better understand the possible impacts and hardening measures.”

In February 2017, EPRI released its first publicly available study to thoroughly examine potential impacts of E3 on large power transformers in the electric transmission system. It concluded that even though an E3 pulse could generate significant currents in tens of thousands of transformers, the likelihood of widespread and long-lasting blackouts from E3 alone was small. A December 2017 study evaluated E3’s potential impacts on voltage stability in the transmission system. Both studies have since been updated with new data from Los Alamos National Laboratory.

The objective of EPRI’s ongoing HEMP research is to inform stakeholders, including utilities that are investing in mitigations and regulators that are crafting policies and rules for hardening substations and other transmission infrastructure. “We are building a technical basis for informing decisions,” said Horton.

EPRI has launched a demonstration project to design and implement hardening measures at more than a dozen utility substations across the United States.

“We are taking a deliberate approach,” said Horton. “Through our upcoming field tests at substations, we can improve understanding of costs, identify unintended consequences, provide engineering solutions, and help address long-term asset management.”

“We also see broad benefits from communicating our findings with other critical infrastructure sectors such as gas, water, and telecommunications,” said Horton. “To date, we have looked at HEMP impacts only on the transmission system, so we don’t want people to conclude that EPRI has solved the HEMP problem. A HEMP would not just hit the transmission system. It would hit everything, and we want to be prepared. We are also planning to investigate impacts on generating facilities and other utility infrastructure across the energy system.”

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