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Geomagnetic Storm Power System Transformer EMP Threat

March 20, 2012, by Ken Jorgustin

North America’s electricity infrastructure is clearly one of our society’s most important assets. As reliance on digital technology and ‘just in time delivery’ distribution systems has increased, many North Americans have come to depend on the reliable delivery of electricity to their homes and businesses to power nearly every aspect of their lives.

The bulk power system is one of North America’s most critical infrastructures, underpinning the continent’s governments, economy and society. As reliance on electricity-dependent technology has increased, the reliability of the power grid has become a necessity to keep most of us alive.

The North American bulk power system is made up of more than 200,000 miles of high-voltage transmission lines, thousands of power generation plants, and millions of digital controls. More than 1,800 entities own and operate parts of the system across North America. These entities range in size from large investor-owned utilities with over 20,000 employees to small cooperatives with only ten. To say the least, because of the numbers involved, there are many various differing methods, configurations, and designs employed within the overall system which add layers of complexity when considering vulnerabilities and solutions to hypothetical problems.


Geomagnetic disturbances, the earthly effects of solar weather, are not a new threat to the electric sector. Recent analysis suggests that the potential extremes of the geomagnetic threat environment may be much greater than previously anticipated. Geomagnetically-induced currents on system infrastructure have the potential to result in widespread tripping of key transmission lines and irreversible physical damage to large transformers. The 1989 event that caused a blackout of the Hydro Québec system proved beyond a doubt of the geomagnetic vulnerabilities and their potential consequences.

The high-altitude detonation of a large nuclear device or other electromagnetic weapon could have devastating effects on the electric sector, interrupting system operation and potentially damaging many devices simultaneously. A coordinated attack involving intentional electromagnetic interference could result in more localized and targeted impacts that may also cause significant impacts to the sector.

The physical damage of certain system components (e.g. extra-high-voltage transformers) on a large scale, could result in prolonged outages as procurement cycles for these components range from months to years. Many of these components are manufactured overseas, with little manufacturing capability remaining in North America.


Intense solar activity, particularly large solar flares and associated coronal mass ejections can create disturbances when this activity is directed towards the Earth. The coronal mass ejection’s solar wind plasma can connect with the Earth’s magnetosphere causing rapid changes in the configuration of Earth’s magnetic field, a form of space weather called a geomagnetic storm. Geomagnetic storms produce impulsive disturbance of the geomagnetic field over wide geographic regions which, in turn, induce currents (called geomagnetically-induced currents or GIC) in the complex topology of the North American bulk power system and other high-voltage power systems across the globe.

Recently, a number of investigations have been carried out (EMP Commission, FEMA under Executive Order 13407, Federal Energy Regulatory Commission , the Departments of Energy, Homeland Security, and Defense). These investigations have been undertaken to examine the potential impacts on the U.S. electric power grid for severe geomagnetic storm events and EMP threats. These assessments indicate that severe geomagnetic storms have the potential to cause long-duration outages to widespread areas of the North American grid.

Most well-known in North America is the March 13-14, 1989 geomagnetic storm. This storm led to the collapse of the Hydro Québec system in the early morning hours of March 13, 1989. Starting at 2:44 AM (EST), operations on the Hydro Québec power grid were normal. At that time a large impulse in the Earth’s geomagnetic field erupted along the U.S./Canada border (Figure 4). This started a chain of power system disturbance events that only 92 seconds later resulted in a collapse of the Québec Interconnection.

Technically speaking…

Telluric currents induced by the storm created harmonic voltages and currents of considerable intensity on the La Grande network. Voltage asymmetry onthe 735-kV network reached 15%. Within less than a minute, the seven La Grande network static var compensators on line tripped one after the other… With the loss of the last static var compensator, voltage dropped so drastically on the La Grande network (0.2 p.u.) that all five lines to Montréal tripped through loss of synchronism (virtual fault), and the entire network separated. The loss of 9,450 MW of generation provoked a very rapid drop in frequency at load-centre substations. Automatic underfrequency load-shedding controls functioned properly, but they are not designed for recovery from a generation loss equivalent to about half system load. The rest of the grid collapsed piece by piece in 25 seconds.

March 13, 1989 blackout – These images depict the ground level geomagnetic intensification over four minutes.

Using the traditional NOAA geomagnetic storm indices, the March 1989 storm was ranked as the third largest storm of all time (since rankings started in 1932). Until recently, many in the electric sector and scientific community therefore believed this storm was representative of the worst case threat that could be posed by geomagnetic storms to North America.

However, recent and more systematic analysis of impulsive disturbances that cause large Geomagnetic-Induced-Current flows has allowed re-examination of the March 1989 storm and other historical storms. This analysis of both contemporary and historic storm data and records indicates dB/dt impulsive disturbances larger than 2000 nT/min have been observed on at least three occasions since 1972 at latitudes of concern for the North American bulk power system. This is an intensity roughly four times larger than the levels experienced in March 1989. In extreme scenarios, available data suggests that disturbance levels as high as 5000 nT/min may have occurred during the geomagnetic storm of May 1921, an intensity roughly 10 times larger than the disturbance levels observed in 1989. Were a storm to occur with these intensity levels, it is reasonable to expect that the bulk power system would experience major impacts. (That’s putting it nicely…)

The demand for electricity in North America has grown dramatically over the past 50 years. To support these energy demands, the EHV (extra high voltage transformers) infrastructure has grown as well. The high-voltage transmission grid presents a complex network topology that couples almost like an antenna through multiple ground points to the geo-electric field produced by disturbances in the geomagnetic field.


The U.S. has 80,000 miles of extra-high voltage (EHV) transmission lines making up the backbone transmission grid that enables the long-haul transport of electricity for our nation. EHV transformers are critical pieces of equipment on the transmission grid. 90% of consumed power passes through a high voltage transformer at some point. If these transformers fail especially in large numbers, therein lies a very big problem. EHV transformers are huge, weighing hundreds of tons, making them difficult to transport – in some cases specialized rail cars must be used (and there is a limited supply of these). Many of the EHV transformers installed in the U.S. are approaching or exceeding the end of their design lifetimes (approx 30-40 years), increasing their vulnerability to failure.


The operating levels of high-voltage networks have increased from the 100-200 kV design thresholds of the 1950’s to the 345 to 765 kV extra-high-voltage levels of today’s networks. As a result, the ratio of resistances varies significantly with voltage class, as the resistance is approximately 10 times lower for the 765 kV than for the 115 kV lines. In general, the higher the voltage rating, the lower the resistive impedance per unit distance (in ohms per km), which will in turn produce ~10 times larger Geomagnetic Induced Current flows in the 765kV elements for the same geomagnetic disturbance environments.

The design of transformers also acts to further compound the impacts of GIC flows in the highvoltage portion of the power grid. While proportionately larger GIC flows occur in these large high-voltage transformers, saturation of EHV transformers occurs at the same level of GIC current as those of lower-voltage transformers. Transformers experience excessive levels of internal heating brought on by stray flux when GICs cause the transformer’s magnetic core to saturate and spill flux outside the normal core steel magnetic circuit.

Well-documented cases have noted heating failures that caused melting and burn-through of large-amperage copper windings and leads in these transformers (Figure 9). These transformers generally cannot be repaired in the field, and if damaged in this manner, need to be replaced with new units, which have manufacture lead times of 12–24 months or more in the world market.


The intention of this somewhat lengthy article is to speak more technically towards the technical aspect of this very real high-impact risk that we face. It is especially concerning as we approach to the peak of the current solar cycle (although not a necessary requirement to receive such a devastating blow from the sun). If you are honest with yourself and really think about the major and absolute dependence that we have on the flow of electricity for our very survival, then this should scare you. Don’t be ‘sheeple’. Think for yourself and do what you can to become more independent of the system.

Without electricity, a high percentage of today’s modern civilization would die within a month, two at the most. It would be unimaginable horror.

Read the book, One Second After, for a reality check.


(Some information sourced from a report of the North American Electric Reliability Corporation and the U.S. Department of Energy’s 2009 Workshop titled, High-Impact, Low-Frequency Event Risk to the North American Bulk Power System)


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