Are Transformers a National Security Risk?

Are Transformers a National Security Risk?

The electric grid uses three types of transformers:

  • Distribution transformers (DTs) are used to bring electricity from the grid to homes and businesses. They range in size from 15 KVA to 5,000 KVA
  • Substation transformers are used to distribute electricity from the transmission lines to distribution circuits where DTs are used. They range in size from around 10,000 KVA to 50,000 KVA.
  • Large power transformers range100,000 KVA upward. The most important of these operate at very high voltages of 340 KV and above and are responsible for wheeling power around the country. See accompanying map.

(Types, in this sense, is not referring to design, such as autotransformers, etc.)

As recently as 45 years ago, virtually all these transformers were built in the United States. I worked for several years at GE’s transformer plant in Pittsfield, Massachusetts.

Today, only DTs are built in any quantity in the United States. Nearly half the DTs are imported. A very few substation transformers and none of the large power transformers are built in the US.

The situation is actually worse, because there is only one supplier in the US of grain oriented electrical steel (GOES), the type of steel currently used in transformer cores. As a result, the cores of DTs built here were probably imported.

The transformer core consists of a steel core made from either grain oriented or amorphous steel, assembled with electrical coils, to form the core which is the heart of the transformer. The core and coil assembly, i.e. core, is inserted into a steel tank and immersed in insulating oil.

The Department of Energy (DOE), is proposing that all DTs be built using amorphous steel for their cores, but once again, there is only one company in the US making that type of steel. Using amorphous steel will reduce eddy current losses which will save utility company’s money over the long term even though the steel is more expensive.

What is the risk to national security if the US doesn’t restore manufacturing of substation and large power transformers?

There have been repeated, though isolated attempts at destroying substation transformers, primarily by shooting holes in the tanks. Bullets penetrating the tanks could cause short circuits, but usually, merely allow the insulating oil to drain from the tank causing the transformer to fail.

So far, only short blackouts have resulted from these attempts, however, a FERC study, reported by the Wall Street Journal, showed that if the “right” set of nine substation transformers were destroyed, it could shut down the grid for a year or more.

But the large high voltage power transformers are even more critical since it takes at least two years to obtain a replacement from a foreign supplier.

Destroying one of these transformers could cause severe disruptions and lengthy blackouts.

Destroying several could cause blackouts across the country lasting for over a year and killing millions.

These transformers are also susceptible to violent solar storms, such as the Carrington event in 1859, and a smaller solar storm in 1989 that caused a power transformer in Canada to fail. Previous articles have discussed the Carrington Event, the danger from an EMP, and terrorist attacks on substations around the country. See 2014 article, End of Civilization, 

It should also be noted that many of the large high voltage transformers are nearing the end of their expected lives.

Over the past ten years, 266 large power transformers were imported from China. It’s not clear how many were of the high voltage type, rated over 345 KV, and it’s also apparently not known where these transformers were installed.

In view of our adversarial relationship with China, and China’s stated intention to replace the United States as the leading superpower by 2050, these transformers would be ideal Trojan Horses.


We are at the mercy of other countries for the manufacture of power transformers. 

Reestablishing the manufacture of large substation and power transformers in the United States should be a high priority. 

Attention should also be given to the manufacture of amorphous and grain oriented steel to be certain we have a supply of these steels made in the US.

While free markets are important, national security interests should take precedence.

Chips are seen as important for national security, but without power transformers there may be no need for chips.

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22 Replies to “Are Transformers a National Security Risk?”

  1. good article and I have no doubt for less than a couple of billion dollars we could secure our transformer future …

    • It will cost a great deal of money, but the survival of the grid will be determined by whether we do what’s needed or not.

  2. Thank you for reporting on a significant national security risk. For those readers interested in the interaction between heliophysics and the U.S. power grid, this technical webpage is a good place to start.
    The owners of Diablo Canyon Nuclear Power Plant near San Luis Obispo, California used an enlightened approach. The plant uses six transformers that produce 500 kiloVolt AC. They have two spare transformers mounted on concrete pads near the working transformers. A good introduction from June 18, 2020 by Chris Said, Ph.D. is at
    See also: “An assessment of threats to the American power grid” by Weiss and Weiss (2019)
    The web link for the 2008 DTIC report cited above regarding transformer vulnerability has changed. See page 41 of 208 of the report at or
    About 4 months ago, the Congressional Research Service released a report, “Ensuring Electricity Infrastructure Resilience Against Deliberate Electromagnetic Threats”

    • Thanks for the additional informations.
      I hope everyone will look through each document to see where we stand with respect to EMP and solar threats.

  3. This subject got a lot of attention in Fall 2022. Then silence, until one March 14 article at WUWT that this year, and now this article.

    My best guess is nut Zero has so many potential problems that people forgot about this pre-Nut Zero problem.

    I read two dozen climate and energy articles every morning and recommend the best of them to my blog readers. This is one of the best today. Donn is the most consistent author I follow. And I thank reader Gene Nelson for the links.

    Richard Greene
    Ye Editor

  4. Donn,
    You are a walking “Power Generation” Encyclopedia. Your articles and books are all well researched and the information presented clearly and concisely. This transformer supply chain issue is a troubling reminder for those of us that have experience in power generation. I remember one of my Mentors, Mr. Mendall Long at CP&L in the 1970’s. Mr. Long chose three single phase main bank transformers with a spare transformer (single phase) sitting on a concrete pad right next to the operating three. When one failed (rarely) it would only take hours or a day to move the failed unit out of the way and roll the spare into place. Mr. Long’s approach remembered about 30 years afterward, when I saw a 200 MW plant experience three phase main transformer bank failure. It took (then twenty years ago) about 18 months to secure a replacement. Since then the supply chain has become more foreign dependent. The recent failures of transformers due to sabotage in NC should be a (another) wake up call to reshore manufacturing. The U.S. needs more experienced engineers in Congress and important Cabinet positions, but not likely 🙁
    Keep up your great writing!

      • I extend my best wishes for your ongoing health. The U.S.A. needs your in-depth power systems engineering knowledge and experience.

        Having spare transformers on-site makes perfect sense for reliability. Unfortunately, as Meredith Angwin notes in her 2020 book Shorting the Grid: The Hidden Fragility of Our Electric Grid the new so-called competitive electricity markets only offer lip-service regarding reliability. As the unreliable performance of the Texas power grid in winter storm Uri (February 13-17, 2021) established, there are no penalties for unreliable electricity. Only exorbitant $9,000.00 / MWh prices.

        • Thanks. I appreciate your comments.
          Texas is the example that keeps on giving. ERCOT knew there would be inadequate baseload reserves two years prior to the blackouts. I reported this my book, published at the sam time as Meredith’s, The Looming Energy Crisis.

          • ERCOT knew in 2011 that the Texas energy infrastructure could not perform properly in unusually cold weather… when unusually cold weather caused 3.2 million Texans to experience rolling blackouts in February 2011. The extreme cold weather problem was first noticed in the 1980s when it was mild.

            The problem in 2021 was not a lack of reserves. The problem was very cold weather again. That weather significantly reduces natural gas production and the natural gas pipelines require electricity to move the gas, which was a design mistake.

            The result, as in 2011, was insufficient natural gas delivered to natural gas power plants. In 2021 that natural gas power plants produced electricity fell about 25% BELOW the pre=cold weather output even as people wanted more natural gas for heat and electricity.

            People with bias and an anti-windmill agenda often try to blame windmills in 2021. That is false. Windmills do what they were designed to do, which can be next to nothing with low or no winds. That happens in just about every week of the year without blackouts. Windmills provide unreliable power output when reliability of the grid is the primary objective — they make no sense for electric grids, unless you enjoy blackouts.

            The 2011 and 2021 Texas blackouts had one thing in common. Once in a decade unusually cold weather limited natural gas supplies. The problem still exists.

            No amount of extra natural gas reserve power plants would have prevented the 2021 blackout because there was insufficient natural gas for the existing plants.

            More nuclear and coal plants would have helped a lot.

            Windmills were not the recommended answer to the February 2011 blackouts (which happened with few windmills in Texas). Even worse than building so many windmills from 2011 to 2021, was buying them without optional blade heaters, So in 2021, half the windmills iced up and had to be stopped during that extremely cold westher.

            I don’t recal the exact number, but Texas used to have about half te reserve capacity s the average US state. To save money I suppose. More reserve capacity would have helped unless it was more natural gas reserve capacity — there simply was insufficient natural gas supplies so more natural gas plants in February 2021 would not have helped.

            Based on ERCOTs poor track record, they need a lot higher interconnection capacity with neighboring grids. The current capacity is very low. Texas needs outsiders to rescue them the next time winter weather is unusually cold because the entire Texas energy infrastructure does not perform properly when the weather is unusually cold.

          • I’m sorry, but I don’t believe you have the full story.
            Yes, the natural gas power plants hadn’t been winterized. Yes, the pipeline NG compressors had been replaced with electric compressors to fight climate change, but then ERCOT shut off the electricity to the pipelines which stopped the flow of natural gas.
            It’s true that ERCOT kept the price of electricity low because they hadn’t built baseload power plants. I pointed that out in my book The Looming Energy Crisis.
            As for interconnections with MISO etc. it would have done no good in 2021 because the weather pattern had almost brought MISO to its knees and MISO had no spare power.
            I have demonstrated in several articles that if ERCOT had had 10,000 MW of reserve baseload capacity, either coal, nuclear or natural gas, it would have avoided the worst of the blackouts.
            I am not in favor of wind and solar because they are more expensive that NGCC plants and harm grid reliability. Again, my book, The Looming Energy Crisis, and Angwin’s book, Shorting the Grid both explain why.

  5. Thank you Donn and as always great information, sad, but information we need to know.

  6. ” but then ERCOT shut off the electricity to the pipelines which stopped the flow of natural gas.”

    I am basing my comments on official reports on the 2011 and 2021 Texas blackouts and EIA information. You are entitled to your own opinions.

    ERCOT had ten years to prepare for the next very cold weather period, from February 2011 to February 2021. Yet they still could not get enough natural gas delivered for their natural gas power plants in February 2021. PRODUCTION of natural gas also declines a lot in very cold weather — see EIA quote below.

    While it was also very cold in Oklahoma when Texas had their 2021 blackout, and I believe 100,000 people in Oklahoma had a blackout too, other states could have provided electricity to Texas if enough high capacity interconnectors existed (as in the EU). Any state with lots of windmills has to have a backup plan with high capacity interconnectors. Windmills are too unreliable to not have 100% natural gas backup that functions properly in ALL weather conditions, or 100% battery backup (unaffordable), or lots of high capacity interconnectors to dustant states. The best design choice is to not add windmills and solar panels to electric grids

    Texas has a population of about 29,5 million. Electricity WAS supplied to about 24,5 million Texans out of the 29.5 million. They needed enough additional electricity to service about 5 million customers.

    Having more natural gas power plants in February 2021 could not have helped because there was already not enough natural gas getting delivered to the EXISTING natural gas power plants in Texas.

    During the 2021 and 2011 Texas blackouts:
    Coal power plants worked
    Nuclear power plants worked
    Windmills did what they were designed to do
    (not many windmills in 2011, but lots of windmills in 2021,
    Both times there was little wind power — that’s just how
    windmills are designed to work. No wind = no electricity)

    There is only one other choice for blame;
    — Insufficient natural gas delivered to
    natural gas power plants in unusually cold weather.

    Why cold weather cut the power in Texas?
    — State officials including Republican governor Greg Abbott initially blamed the outages on frozen wind turbines and solar panels. Data showed that failure to winterize power sources, like wind turbines and natural gas infrastructure, had caused the grid failure.


    “During the cold snap that affected much of the central part of the country, U.S. dry natural gas production fell to as low as 69.7 billion cubic feet per day (Bcf/d) on February 17, a decline of 21%, or down nearly 18.9 Bcf/d from the week ending February 13.

    Natural gas production in Texas fell almost 45% from 21.3 Bcf/d during the week ending February 13 to a daily low of 11.8 Bcf/d on Wednesday, February 17, according to estimates from IHS Markit.

    Temperatures in Texas averaged nearly 30 degrees Fahrenheit lower than normal during the week of February 14.

    The decline in natural gas production was mostly a result of freeze-offs, which occur when water and other liquids in the raw natural gas stream freeze at the wellhead or in natural gas gathering lines near production activities.

    Unlike the relatively winterized natural gas production infrastructure in northern areas of the country, natural gas production infrastructure, such as wellheads, gathering lines, and processing facilities, in Texas are more susceptible to the effects of extremely cold weather.

    “After reaching a daily low on February 17, 2021, natural gas production in Texas began increasing as temperatures started to rise. Daily production reached an estimated 20.9 Bcf/d on February 24, only about 0.3 Bcf/d lower than the average in the week ending February 13.

    • My opinions are based on facts.
      While much of your post provides facts as reported by others, the EPA and EIA are hardly unbiased observers. It’s their policy to promote wind and solar to fight climate change.
      I doubt whether interconnects would make much difference, but I don’t think they hurt. (Haven’t studied that aspect of the grid, so can’t be sure that it might result in cascading failures.) It certainly goes agains the idea of micro grids.
      My article in May of 2021 at summarizes the situation while also mentioning that Berkshire Hathaway agreed with me.

  7. The authorities all admitted that wind energy was unusually low.

    ERCOT supposedly had a contingency plan for wind power at 6% of nameplate capacity as the lowest possible week in the winter. The actual output went down to 4% of nameplate capacity, although not for a full week. I assume the number would ave been 8% if not for half the windmills having icing problems. But 4% and 6% were not that much different.

    Since Texas could not supply their existing natural gas plants with enough natural gas in February 2021, the electricity output from natural gas fell about 25%, and because of that there were blackouts. Additional natural gas power plants in 2021 would not have helped — they would not have been able to get the natural gas they needed (because actual, existing 2021 plants could not get enough natural gas).

    The Texas blackouts made ERCOT look bad, along with the natural gas infrastructure (but not the actual natural gas power plants), windmills and solar panels too. Coal and nuclear power plants looked good. Natural gas power plants would have looked good if they could have received enough fuel.

    I believe the data I used for my conclusions were accurate.

    I do not take advice from an investment company like Berkshire Hathaway, just because they own some oil stocks.

    I guess we are going to disagree on this issue.

    We’ll have to send this conflict to the UN.