A new Electric Power Research Institute (EPRI) report finds that a limited number of bulk-power transformers would be at potential risk of thermal damage due to a single high-altitude electromagnetic pulse (HEMP) attack, but that additional work is needed to fully investigate the impact to the entire bulk-power system.
HEMP is caused by the detonation of a nuclear weapon above the earth’s surface and is characterized by 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. Potential impacts can range from damage to electronic components and insulators (E1 and E2) to voltage collapse and transformer damage (E3).
The EPRI report, “Magnetohydrodynamic Electromagnetic Pulse (MHD-EMP) Assessment of the Continental U.S. Electric Grid: GIC and Transformer Thermal Analysis,” evaluated the E3 grid impacts from a single high-altitude nuclear burst over 11 target locations. It included a geomagnetically induced current (GIC) analysis and transformer thermal assessment.
The study used modeling and assessment techniques and included bulk-power transformers, which convert high-voltage electricity from one transmission voltage to another enabling it to move from a generation source to the end user. It found between 3 and 14 transformers would be at potential risk of thermal damage; however, the risk from thermal damage does not suggest that they would be rendered inoperable during an E3 event. Rather the results indicate that while transformers may be at risk of damage, further analysis would be needed to understand the extent of damage using asset and system specific data, including the condition of the transformer.
“HEMP is a complex and challenging issue,” said Rob Manning, EPRI vice president of Transmission and Distribution. “This report provides the technical basis that is needed before an effective strategy to mitigate the effects of HEMP can be developed. There is still a lot of work to be done in order to better understand how HEMP may impact grid reliability and recovery efforts.
“This assessment indicates that the failure of a large number of bulk-power transformers due to thermal damage from E3 is unlikely. But the study results should not be interpreted to indicate that it is not a potential problem since impacts related to widespread outages due to voltage collapse are still being investigated,” he said.
In April 2016, EPRI, in collaboration with the U.S. Department of Energy (DOE), started a comprehensive three-year research project to provide a technical basis by which electric companies can address the HEMP threat by evaluating potential impacts, hardening and mitigation options, and recovery plans. (To see the DOE project outline click on this link.)
EPRI is also collaborating with utilities and several national laboratories. To view the report, click on this link.