Analog Angle Blog

When Lightning Strikes, Will a Surge Protector Help?

Recently, a thunderstorm fried my PC’s power supply and its motherboard. Although I wasn’t home at the time, I am pretty sure it was the storm and lightning-related surge of some type that did it, and not a random or coinciding failure, since a printer and cable modem on the same AC line were also zapped. Further, I know it was more than the supply, since a vendor-supplied replacement ($40, two minutes to swap it) did not bring the PC back to life.

I am not sure of the “mechanism” by which the lightning came into the system or what the surge (or whatever) looked like – that can only be done with the appropriate instrumentation connected at the time, of course. None of the other electronics on nearby circuits were affected, not even the cheap AC-line powered clock nearby which usually resets to 12:00 after even a momentary brown-out, when the nearby lights flicker for a moment.

OK, these things happen. In these situations, it’s customary to consider not having it happen again, even if it is too late this time. The power strip into which these items are plugged had a label proclaiming it has built-in “surge protection” but of unspecified rating. If I was going to get a separate surge protection device (SPD), I thought it made sense to do some research to assess what rating(s) would make sense.

Perhaps it shouldn’t be a surprise, but I came away confused. Why so? Certainly, surges and transients are inherently confusing topics. First, it’s not really a surge protector or surge suppressor, as they are called in mass-market consumer literature, a more-accurate name would be a transient protector. There’s also a difference: a surge arrester directs the higher-voltage transient to ground, while a surge suppressor absorbs the energy and re-emits it as heat.

Then there are three non-nomenclature issues: how much of this so-called surge protection do you think you need, how to get it, and where to put it? For the first question, numbers were all over the place. Blogs and sites of questionable credibility recommended 200, 400, and even 600 joules. I wasn’t looking to protect my equipment from a direct lightning strike to the house, just from line-related problems. None of them mentioned that it is not just the joules “energy” rating that matters, but also the time over which that energy is spread. There are industry and regulatory standards for that, such as UL1449, “Standard for Surge Protective Devices.”

On the other hand, the credible sources spent a lot of time discussing important issues of whole-site protection (house, office building, or industrial plant) which wasn’t my concern at this point. The basic options were protection by open circuit or by short circuit. This would be accomplished by voltage-breakdown devices (gas discharge tubes and spark gaps), voltage-limiting devices (metal oxide varistors or avalanche diodes), bandwidth suppressors (various filters, inductors and capacitors), and even isolation devices (opto-isolators and fiber optics – clearly not applicable for the problem) as the principle technologies. They also pointed out that a single protection device or subsystem located far from the device to be protected or its AC outlet may not actually be able to protect, given the nature of lightning surges and reflections.

Then there were several other concerns, assuming I even decided what to do. Credible sources noted that some types of SPDs do wear out from stress due to repeated “hits,” even those that were within their ratings; some suggested replacing the SPD every few years. Worse, some sources called out a report from NEETRAC (the National Electric Energy Testing, Research, and Applications Center) in Atlanta, GA which said that many surge protection devices failed to perform according to ANSI, IEEE, UL, IEC or other required specifications (sorry, I couldn’t find the report itself at their site).

Frankly, that last bit of bad news didn’t surprise me at all. It’s not news that there are lots of fake or substandard components and devices out there. How hard would it be for a vendor of SPDs – especially the cheaper ones you get at big-box stores, to substitute these after getting the UL or similar certification? After all, passives such as those in an SPD are easy to fake, and even dummy units will “work” just fine, until they are called upon to actually protect anything (it’s the same with batteries, of course).

The dilemma with SPDs is that the average user has no way to test the unit, so it’s easy to have false confidence in the one you are using. Further, if you could test your SPD, the tests are either stressful and degrade performance, or are destructive, depending on the SPD. Therefore, you must rely on the vendor credibility and assume (hope?) they do sampling tests of the materials, components, and end product. If the SPD fails to do its job, the vendor can simply claim the surge energy exceeded its ratings, a claim which is impossible for consumers to disprove.

So, what to do? I am still in a quandary, for sure. Until I decide, I’ll rely on the best surge-protection tactic I know: unplug the PC when a storm is imminent, or when I leave for an extended time and the forecast incudes thunderstorms. Perhaps this is not an elegant solution, but it is an effective one.

Do you have any experience with, or suggestions about, surge protection for individual units such as PCs in a residential setting, and SPDs in general?

Related Internal Content

Counterfeit Parts: It’s Worse Than We Thought

Teardown: A19 LED bulb

Megavolt/kiloamp tests reveals extreme engineering challenges

External References

Lightning surge protection: Two is better than one!

Importance Of Lightning Surge Protection Devices

The Surge Protection Device (SPD)

NLSI Recommendations for Surge Protection Devices

7 comments on “When Lightning Strikes, Will a Surge Protector Help?

  1. vbiancomano
    September 2, 2018

    When it comes to lightning , my experience is that it's more risky to depend on surge protectors than not to use them at all. That is, surge protectors continue to provide the user with a false sense of security, because the surge energy of a future hit can be as large as one provided by a direct hit (from which very little survives), let alone a bolt that strikes down the street. In that sense, they're often a waste of money as a protection device for lightning , even IMO if high-capacity units are placed at the house's main breaker. With potentially high-risk storms, my solution is to unplug all devices and systems from the mains and shut down the house breaker as well. I also disconnect as many other leads as possible coming into the house (e.g., antennas) from any devices that are grounded, with the hope (not yet confirmed as right or wrong) that the theory of offering an open-circuit device to the lightning will discourage a charge to flow. Then again, do we consider the lightning a small-area constant-current source? There's always unknown elements.

  2. Steve Taranovich
    September 2, 2018

    Thanks Vince, for the added tips! 

  3. Romano.Eduard
    September 3, 2018

    The SAd device can be installed on some specific sections of overhead lines that are especially subject to direct lighting strikes and should as well be installed within the last 3 or 4 spans before substations.

    You can read about solutions here

  4. DaveR1234
    September 5, 2018

    My house was recently hit; the belief was that a transformer primary line fell on the secondary.  Two appliances and a number of wall warts and dimmer switches got fried;  house is still standing so it could have been a lot worse.  It got me thinking about what is the best way to protect all the electronic devices we have tied to the power lines.  I don't feel a MOV to ground can possibly be expected to absorb the energy of my particular surge or a lightening surge unless it is rated to trip the circuit breaker.  What does it take to trip a breaker?  Do MOVs and breakers have an I^2t rating?  MOVs appear to have a limited life; what happens when they reach end of life? Do they go short or open (neither is good)?

    Maybe this is a good business opportunity. 

  5. analog_john
    September 5, 2018

    Bill, thanks for the article. 

    I've had good luck with Isobar surge protector power strips from Tripplite.  They are built like a tank, have a steel case, and are made in the USA.  We used them in the EE and Computer Science departments at Oregon Graduate Institute for 20 years without any equipment failure.  We had one leg ot the 3 phase power to the building fail.  It blew out about 10 Isobars, but they sacrificed themselves for the computer equipment all of which survived.  I use them at home where they have protected from many power line surges, though we don't get much lightning in Portland.

    To the point of your article, the Isobar8ultra has LED diagnostic indicators that indicate LINE OK,  FAULT, PROTECTION PRESENT.  With the “PROTECTION PRESENT” LED you have some confidence that the MOVs are still intact, which was a major point of your article.

    I have no affiliation with Tripplite other than being a satisfied customer for many years.

    Google isobar8ultra for details.  Their web page says:

    Tripp Lite will repair or replace any connected equipment damaged by surges, including direct lightning strikes, up to $50,000 for life.

    John Hunt

    Portland, OR


  6. SpatialKing
    October 1, 2018

    One engineer I worked with had his house hit by lightening.  It hit the bricks in the chimney.  No wires were fried but it did fry everything in the house, including light bulbs that were off, things that were unplugged, and even fried the motor in the fridge.   Folks talk about maybe getting hit but they neglect to mention where the hit occured or will occur.   The closer it is then the energy increases at an expontential rate.  

    Clearly at some distance, good surge protectors will help, but at some point, they no longer matter.


  7. October 19, 2020

    Thank for your writting. We are a lightning protection construction company. In all projects, we always advise customers to use surge protection systems. This is indeed the system that brings many benefits to both families and construction works in general. They protect electrical appliances in the home and help customers feel more secure when storms come.
    Our country has dozens of big storms a year. This is a great solution to ensure safety for your family.
    You can refer to many of our articles on the website: https: //

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