{"id":48476,"date":"2026-03-15T08:33:10","date_gmt":"2026-03-15T15:33:10","guid":{"rendered":"https:\/\/brainfiller.com\/?p=48476"},"modified":"2026-03-15T09:17:40","modified_gmt":"2026-03-15T16:17:40","slug":"japan-earthquake-arc-flash","status":"publish","type":"post","link":"https:\/\/brainfiller.com\/es\/nfpa-70e\/japan-earthquake-arc-flash\/","title":{"rendered":"9.0 Earthquake | Fukushima | Arc Flash | and Me"},"content":{"rendered":"
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Fifteen years ago on March 11, 2011, a devastating earthquake struck Japan with a magnitude of 9.0. Little did I know at the time that I would become part of the international investigation team.<\/p>

Most people remember two things: the devastating tsunami and the disaster at the Fukushima Daiichi nuclear power plant. But there was another event that almost no one talks about\u2014an arc flash<\/strong> at a different nuclear power plant. The Onagawa Nuclear Power Plant.\u00a0\u00a0Wait\u2026 what?<\/strong><\/p>

The massive earthquake caused violent ground motion across northeastern Japan. The Onagawa Nuclear Power Plant, was actually the closest nuclear facility to the earthquake\u2019s epicenter. Despite the extreme shaking, the plant\u2019s structural systems performed remarkably well. But something unusual happened inside.<\/p>

During the earthquake, a fire broke out in a 6.9 kV switchgear lineup at Unit 1.<\/p>

A fire? Inside a nuclear plant? During an earthquake? Naturally, people wanted answers.\u00a0<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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Ready to go with the test. Wireway filled with insulated cables<\/figcaption>\n\t\t\t\t\t\t\t\t\t\t<\/figure>\n\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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Success! The damage looked similar to the Onagawa switchgear<\/figcaption>\n\t\t\t\t\t\t\t\t\t\t<\/figure>\n\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t
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The International Delegation<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t
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The Japanese government assembled an international team to investigate what happened. Experts from Japan Nuclear Energy Safety Organization (JNES), the U.S. Nuclear Regulatory Commission (NRC), Southwest Fire Research Institute, as well as a few other international organizations, …and me.\u00a0 As it turned out, I was the only one from the delegation that had a background in arc flash.<\/p>

Together, the goal was to determine the answer to the puzzling question:<\/p>

How can an earthquake start a fire inside nuclear power plant?<\/strong><\/p>

One of the early meetings was held just outside Philadelphia. The Japanese delegation walked us through the sequence of events at Onagawa. They had photos, timelines, equipment damage reports. \u00a0People began floating all kinds of theories about how the fire started but honestly, none of the explanations I was hearing made much sense from an electrical standpoint.<\/p>

Then one slide popped up during the presentation. It was a photo of the damaged switchgear bus bars. They were seriously distorted.<\/p>

And at that moment\u2026 Ding ding ding. <\/strong>I think I just figured it out from only one photo.<\/p>

I asked a simple question: \u201cHow did the bus bars become deformed?\u201d<\/strong> The assumption in the room was that the intense heat from the fire warped them. OK, here comes my follow-up question: \u201cIf heat caused the deformation\u2026 how did the top bus bar bend upward?\u201d<\/p>

Silence – No one knew.<\/p>

So I opened my laptop and pulled up a high-speed arc flash video showing bus bars during a high-current fault. When massive short-circuit current flows through parallel conductors, the magnetic forces can be enormous. The Lorentz forces between conductors can cause bus bars to bend, distort, and repel each other. \u00a0<\/p>

So I now floated my theory.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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9.0 Earthquake and Arc Flash<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t
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A magnitude 9.0 earthquake is hard to comprehend \u2013 I can not even imagine. The ground doesn\u2019t just shake\u2014it violently accelerates structures in multiple directions.<\/p>

So what if the seismic motion caused something inside the switchgear to shift and bus bars to flex?<\/p>

What if:<\/p>

  1. The earthquake shook the metal-clad switchgear.<\/li>
  2. Bus bars momentarily contacted each other.<\/li>
  3. That created a short circuit.<\/li>
  4. As the bus bars separated, the fault escalated into an arc flash.<\/li>
  5. The arc flash energy ignited cable insulation or other combustible materials inside the gear.<\/li><\/ol>

    That arc flash could release enormous energy\u2014heat, vaporized metal, pressure waves, and molten particles. In nuclear safety terminology, this type of event is called a High Energy Arcing Fault<\/strong> (HEAF).<\/p>

    Someone in the room then asked me: \u201cWhat is an arc flash?\u201d So I ended up giving an impromptu arc flash tutorial to an international nuclear investigation team. Not something I expected when I woke up that morning. But after a long discussion, the group agreed: This was a plausible mechanism – and we needed to explore it further.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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    Arc Flash Testing - The Plan<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t
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    A full-scale test program was developed to see whether an arc flash could produce the kind of sustained fire observed at Onagawa. While traditional arc flash testing focuses on things like: Incident energy and Arcing current, the nuclear industry had a different concern. They wanted to understand the Zone of Influence<\/strong> (ZOI)\u2014how far the effects of a high-energy arcing fault could spread beyond the equipment enclosure.<\/p>

    I\u2019ve been involved in a lot of arc flash tests over the years. Some were very impressive, but not as impressive as what was about to unfold with these tests. The most dramatic one I was ever responsible for was about to occur and involved 15 kV switchgear operating around 7 kV – very similar to what existed at the Onagawa plant.<\/p>

    The objective was simple: Can an arc flash ignite insulation and create a sustained fire?<\/p>

    We had three days. Each day followed the same routine:<\/p>

    1. Install new switchgear<\/li>
    2. Add instrumentation and calibrate the test circuit<\/li>
    3. Set up high-speed cameras<\/li>
    4. Configure the fault<\/li><\/ol>

      Then during the last hour…<\/p>

      Three \u2013 Two \u2013 One – KA-BOOM!<\/strong><\/p>

      Day 1<\/strong> On the first day, we got a spectacular arc flash complete with a huge plasma, molten metal, blast pressure, a fire and major damage. But the fire didn\u2019t sustain. Exciting and disappointing all rolled into one.<\/p>

      That night I went back and studied the video footage as a postmortem. Why no sustaining fire? We decided to tweak the trigger wire configuration and arc duration<\/strong> to increase the energy release.<\/p>

      Day 2 <\/strong>The next test was even more spectacular. The arc ignited, the plasma and thermal energy blasted out of the gear, and for a moment everything went quiet.<\/p>

      Then I noticed a little flicker behind a hole where there used to be a pistol grip:<\/p>

      \u201cWait\u2026 is that a fire?\u201d<\/strong> I exclaimed?<\/p>

      Yes, A small flame appeared. Then it grew. And grew. AND GREW! It became quite an inferno.\u00a0 The switchgear was sitting a few inches off of the ground and the wire way shown in the photo, was packed with cables that caught fire.\u00a0 We had the perfect chimney effect. Air entering from the bottom and the wireway acting as a flame thrower towards the ceiling!<\/p>

      Then someone from the delegation turned to me and asked: \u201cMr. Phillips\u2026 how do we extinguish this fire?\u201d<\/strong><\/p>

      For a split second I panicked. Then I realized something. I had been brought in to create the arc flash and sustained fire<\/strong>, not to figure out how to put it out. So my response: I have no idea!<\/p>

      Be careful what you ask for.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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      Testing the theory<\/figcaption>\n\t\t\t\t\t\t\t\t\t\t<\/figure>\n\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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      Amazing damage!<\/figcaption>\n\t\t\t\t\t\t\t\t\t\t<\/figure>\n\t\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t
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      The Ultimate Fire Drill<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t
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      I was concerned we were going to burn the lab down. The lab was not prepared for such a fire.\u00a0 However after about 15 minutes of controlled chaos, the fire was finally extinguished. How? The old-fashioned way. A garden hose. Fortunately, the equipment had already tripped offline and been electrically isolated, so there was no electrical hazard during the firefighting.<\/p>

      A side story<\/strong>: I was discussing this event recently with a person at a conference. When I got to the description of the fire and fear of burning down the lab,\u00a0 his face lit up and exclaimed; \u201cSo you\u2019re the one!!\u201d<\/strong>\u00a0\u00a0 What?\u00a0 He said he was just at this lab and someone there was telling the story of a person that came close to burning the lab down.\u00a0 OK, I guess that is my claim to fame.<\/p>

      But the test DID<\/strong> prove something important. HEAF events can release enormous energy in milliseconds and may eject hot gases, molten metal, and debris that ignite nearby combustible materials.<\/p>

      The Onagawa switchgear fire became a major case study for the nuclear industry. It demonstrated that arc-flash-driven HEAF events can cause fires and mechanical damage extending well beyond the equipment enclosure, which led to new international research programs and regulatory attention focused on understanding and mitigating these hazards.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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      From Earthquake to Arc Flash<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t
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      The 2011 earthquake taught us many lessons. One of them was something few people expected: A seismic event may trigger a high-energy arc fault inside electrical equipment<\/strong>, which can then ignite a fire. That realization helped drive new research, testing programs, and safety improvements across the nuclear and industrial electrical world. And it all started with one photo of bent bus bars.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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      To Learn More...<\/h2>\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t
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      To learn more about IEEE 1584, Arc Flash Studies and Medium Voltage Power Systems, check out a few of Jim Phillips’ Scheduled and On Demand training programs below.<\/p>\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t

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      \n\t\t\t\t\t\n\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\tIEEE 1584 and Arc Flash Studies <\/span>\n\t\t\t\t\t<\/span>\n\t\t\t\t\t<\/a>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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      \n\t\t\t\t\t\n\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\tSistemas de energ\u00eda de media tensi\u00f3n<\/span>\n\t\t\t\t\t<\/span>\n\t\t\t\t\t<\/a>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t
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      \n\t\t\t\t\t\n\t\t\t\t\t\t\n\t\t\t\t\t\t\t\t\tCapacitaci\u00f3n a pedido <\/span>\n\t\t\t\t\t<\/span>\n\t\t\t\t\t<\/a>\n\t\t\t\t<\/div>\n\t\t\t\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t\t\t\t<\/div>\n\t\t\t\t<\/div>\n\t\t
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      With a career beginning in 1981 and Brainfiller launching in 1987, Jim has built a global reputation as a trusted leader in electrical safety.<\/p>

      He currently:<\/p>