did you ever see a plasma ball fly out of a power strip? - Page 1
Forum section: electronics / general

author: coppercone2
author_rank: Super Contributor
timestamp: March 15, 2021, 12:34:51 am
content: So my power went out and when it came back on this all metal Lowes brand power strip spit out a fireball into the middle of the living room (looked like welding splatter from a dirty job). When I took it apart later it look like a standard damaged MOV type deal. The power strip was on a table facing a wall so it must have shot a fireball into the wall then bounced it off the drywall into the room.What I don't get is that its pretty well sealed/tight and the MOV is far away from the outlet receptacles. How does something make it all the way there? I feel like an ant could have had trouble getting there through that maze of shit. The seal on the power strip was good tight metal fit, so the only place it coulda came from was the holes.A triplite also got damaged but I did not see what happened, it just looks really fucked up inside with MOV soot. They shattered/exploded btwThis was ~ 1 year old, contractors grade with the heavy rubber cord, attached to a little bedside table with a lamp and a clock on it. I took apart the clock and looked at the lamp light bulb (its very simple) and there was no problems. I know it was clean because it was attached under the table protected from dust by the table top in an area where normally nothing happens so I know there was nothing in the socket.The trajectory was really weird too because it must have traveled in like a logarithmic spiral or something.I have seen videos of I think silicon sparked with alot of energy to make some kinda plasma ball shit so I wanna think maybe the material in the MOV did it. But it was not a menacing white ball, it was like orangeiush and rather small but when I saw it I knew what it was.this must be the source,https://www.digikey.com/en/products/detail/bourns-inc/MOV-20D201K/2799097?utm_adgroup=Circuit%20Protection&utm_source=google&utm_medium=cpc&utm_campaign=Dynamic%20Search_EN_RLSA_Buyers&utm_term=&utm_content=Circuit%20Protection&gclid=CjwKCAiAhbeCBhBcEiwAkv2cY7Nj-BGjxjWTHtIdaMadEM-j_QlTepGD0Tl-1ReS6YFqvY8u0fT3JBoCX6cQAvD_BwEit looks like 3 in parallel with 1 blown

author: SilverSolder
author_rank: Super Contributor
timestamp: March 15, 2021, 01:54:57 am
content: Wow, sounds like an underwear-replacement-required event...

author: coppercone2
author_rank: Super Contributor
timestamp: March 15, 2021, 02:12:23 am
content: Basically I have a living room/kitchen connected by a open double wide door in this small houseThe table and the refrigerator are on the same circuit (it is done according to the wall not the room), I noticed when the power went out I went to go clean because it was like too dirty to wheel the generator out, and I got a little winded moving a snow blower back to the shed up hill, then the power came back but the fridge was off so I flipped the breaker that was off and it either quietly reset or reset while I was walking up the stairs, when I was upstairs my family member was down stairs so I yelled to try to turn it on again (I thought maybe I was being too gentle with the reset or something), and when they did I saw it happen.It was not scary because it was a little low energy (maybe its just because I have experience with a cheap ass arc welder), but the ramifications of that making it into a box of tissues that I normally keep on the table would be potentially very bad. I did not see exactly where the ball traveled until it was in plain sight in the middle of the living room, because maybe the lights flashed or I was just thinkin about the refrigerator too hard or somethingSo it must have traveled from the MOV down one of the folded crimps, out the hole, near or bounce off the wall then arc fly to the middle of the room.I don't see any signs of arc damage to the contacts when I look down em, and the whole thing is sealed tight. The PCB is far away because it has light pipes going to the LED that are hot glued into place. The bottom of the glue on the light pipes is scorched but not the top. The other possibility is that it maybe made turbulance which made the light pipes deflect down and make a temporary hole for the plasma ball before going back into place but it seems dubious that it can happen. The tripp-lite actually took way more internal damage but it was at my computer bench so I don't know what happened under the table.. I think those are sealed better though. This one has like a long crimp thing that is hollow instead of individual outlets.The folding of the metla is actually high quality on this, I can assure you that the chassis was tight, it HAD to either some how form outside or travel outside through some complex path. Maybe they skid over a ground plane like a circuit rail gun thingy?Edit I wanna say I saw it when it was OVER the table the power strip is mounted on but I could not tell where it came from but the only damaged thing is the power strip, the clock works fine and I took it apart and it just has a little transformer anyway and the light bulb is sealed and the lamp is the most simple lamp and it was screwed in tight and it was moving upwards at a lower elevation then the lamp so it could not have came from the lamp. The outlet had 2 plugs so it could not have come from there and the MOV is like shattered so I assume it went from the MOV and out one of the grounding holes.What do you call this phenomena?And yea when its screwed in and tight there is still a hole for the ground pin big enough for a large ant. the brand name is PRIME 101418 UTPB 2135

author: amyk
author_rank: Super Contributor
timestamp: March 15, 2021, 02:32:52 am
content: https://en.wikipedia.org/wiki/Ball_lightningPictures please...

author: coppercone2
author_rank: Super Contributor
timestamp: March 15, 2021, 02:35:11 am
content: of what? there is a cracked mov and some soot

author: coppercone2
author_rank: Super Contributor
timestamp: March 15, 2021, 02:38:36 am
content: i got one close up to give maybe an idea of energy levels involved. some pieces came out of the chassis when openedI see the better ones are wrapped with kapton but that will do fuck all I think. I bought a replacement trip light online. I think its worth it, it has some coils and shit maybe to slow things down a little. fucking lowes

author: coppercone2
author_rank: Super Contributor
timestamp: March 15, 2021, 02:44:16 am
content: here is the other strip from trip lite (plasma cannon not suspected)the fault light turned on after the power surge,It looks like maybe that one made more soot but I think the MOV looks to be in better condition despite being torn open. And its physicality built like 500 times better. The trip lite is also on a newer wire on its own circuit breaker without more crap on it so I assume it took a bigger hit also.. that one was connected to another sony wall clock, a 27 inch monitor and a cell phone charger.not to distract from the issue of shit shooting out plasma balls like a fucking imp from doom but maybe those pictures might give someone an idea of the voltage/power levels involved in the surge.. i personally have no idea. nothing else in the house appeared to break that i noticed

author: coppercone2
author_rank: Super Contributor
timestamp: March 15, 2021, 02:49:35 am
content: looking at the two pics it makes me kinda think like all those magnetics tame it down a little bit, especially since the less damaged one is on a shorter new piece of nicely tightened romex going only to that outlet direct from the circuit boxLike the tripp lite has metal on it but the other one looks like there is nothing left? not that i care so long again its not shooting plasma balls.yeah i guess im traumatized i wanna put my tissues in a steel box now

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: March 15, 2021, 03:16:56 am
content: I remember some random dude from a long time ago shorting out large batteries and calling it "ball lightning"Fun!

author: coppercone2
author_rank: Super Contributor
timestamp: March 15, 2021, 03:23:04 am
content: yea thats it, at much higher power.good reason to keep your house tidy and put linens away into the cabinet and stuff like that. maybe i will find a classy metal tissue box because its seriously pissing me off. Couch is leather so it should be OK.damn this is like being punched in the nuts you think its a sunday and your looking for charred bullshit the rest of the day

author: CatalinaWOW
author_rank: Super Contributor
timestamp: March 15, 2021, 03:33:49 am
content: Was there a burn spot where the ball landed in the middle of the room? If not, it is possible that there was merely a flash of light out of the power strip and the rest was an after image resulting from the bright flash in your dark adapted eyes.There is a reason that ball lightning and other plasma ball phenomena are rarely if ever documented.

author: coppercone2
author_rank: Super Contributor
timestamp: March 15, 2021, 03:43:01 am
content: nah it did not flash I just saw the ball, I am used to seeing them because its verysimilar(not identical) to arc welding splatter. It extinguished before it landed. The power strip is underneath the table mounted to the table leg and support bracket facing a eggshell texture medium blue wall, its not flashing or reflecting any light off that. The explosion was contained in a metal box so it cannot flash anyway.looked like a dim little sun or something, I caught it when it was traveling over the table (not sure how it go there) and towards the middle of the living room before it dropped. I stood there for a while looking to see if I could see any smoke come from the hardwood floor near where the parabolicish trajectory endpoint projected landing zone but I dunno what the fuck it was, for all I know there is no 'core'. I watched some stuf about it now and people say the big ones end with a explosion and they disappear into thin air. but mine just dimmed out of existence.I have a good idea of what bright lights to do eyes (again, lots ofwelding), its nothing like that related to bright flashes. Its a nice subdued day and I got up at like 2pm so I was nice and restedthe problem is the floor has not been refinished in like way too long and its a real shitty surface finish so evidence is gonna be hard to findthat guy should spark the stuff over a sheet of glass so he can find out what the lighting balls do after they burn up.

author: Nominal Animal
author_rank: Super Contributor
timestamp: March 15, 2021, 11:17:49 am
content: True ball lightning is real but rare, and has been demonstrated in laboratory considitions since 2004 at least.Theory I think is most plausible is that the plasma forms some kind of structure that holds it together; it does not necessarily have any solid parts at all. Something similar to the Leidenfrost effect, where a vapor layer separates a liquid and a solid, allowing one to e.g. dip a (moist) bare hand in molten lead (say 725 K) for a fraction of a second without getting burned (as shown on e.g. Mythbusters).In particular,R Morrow 2018 J. Phys. D: Appl. Phys. 51 125205describes the separation as caused by positive ions driven away, and negative ions into the "ball" as the separation mechanism, and the light as mainly caused by the negative ions burning. Such structures can last ten seconds, while the amount of material involved is neglible, definitely less than typical welding spatter. (I'm a horrible welder, though.)That model is interesting because it also kinda-sorta explains the stories of ball lightning after lightning has hit a chimney, because carbon soot and silica is involved (carbon soot from burning, and silica in the rocks/bricks) – carbon (soot) seems to be a necessary ingredient, and the two used in the laboratory production of ball lightning. The thunderstorm itself provides suitable atmospheric conditions for ionization in general. Prior to widespread introduction of lightning rods, lightning would have struck chimneys much more than they do nowadays. At least all the historical reports of ball lightning I've heard in Finland, have involved lightning hitting a chimney (or very similar conditions).That said, not all reports of ball lightning are ball lightning, but more biophysical effects from bright flashes ("afterimages"). Also, when people experience an adrenaline surge, their perception of time can be very distorted: an event that takes a fraction of a second, can feel like several seconds. (I've had that happen to me once, with a wound that cut open a surface blood vessel requiring stitches. I vividly recall calmly examining the first droplet of blood flying in a beautiful ballistic arc, as if in slow motion, before everything sped back up to normal speed.)

author: SilverSolder
author_rank: Super Contributor
timestamp: March 15, 2021, 12:14:17 pm
content: Quote from: Nominal Animal on March 15, 2021, 11:17:49 amIf you read TinTin as a kid, you know that ball lighning is real and comes in through chimneys, LOL!

author: Nominal Animal
author_rank: Super Contributor
timestamp: March 15, 2021, 01:18:37 pm
content: Quote from: SilverSolder on March 15, 2021, 12:14:17 pmHa!But no, Hergé just used the existing tales in his story. For example,"Globe of Fire Descending into a Room" in "The Aerial World," by Dr. G. Hartwig, London, 1886. P. 267. Library Call Number QC863.4 H33 1886. Image ID: libr0524, Treasures of the NOAA Library Collection:Another common thing is passing or appearing through a window (silica glass). The interesting thing is how silicon and carbon form nanostructures whose properties can be modified by doping with iron, calcium, and oxygen. Some researchers have actually captured the spectrum of a suspected ball lightning in nature (Jianyong Cen, Ping Yuan, and Simin Xue, Phys. Rev. Lett. 112, 035001 – Published 17 January 2014).

author: coppercone2
author_rank: Super Contributor
timestamp: March 15, 2021, 02:04:06 pm
content: it must be something with the carbide? MOV. I found a broken clock and a 3rd fried power strip. This was really strong.the only adrenaline rush I got was from buying the replacement power strips because tripp lite is so expensiveim sorry but this 'flash' theory is incorrect. buy one and see that thing CANNOT flash. And it was mounted under the table facing a wall that is 3 inches away with a lamp in the way. I was not effected by some kind of lights, its not even a thunder storm, it was a nice day just real windy

author: SilverSolder
author_rank: Super Contributor
timestamp: March 15, 2021, 04:21:45 pm
content: Quote from: coppercone2 on March 15, 2021, 02:04:06 pmTripp lite is good stuff, it's what I use everywhere too. It isn't exactly cheap, as you say, but they are a once-in-several-decades purchase...

author: Nominal Animal
author_rank: Super Contributor
timestamp: March 15, 2021, 05:28:30 pm
content: Quote from: coppercone2 on March 15, 2021, 02:04:06 pmIn case you are referring to me, I wasn't suggesting that; quite the opposite.Laboratory ball lightning experiments use high voltage, and carbon and/or silicon, and some metal. You could say that the effects of a lightning strike on the power lines vaporizing a MOV is pretty damn close.Because of that, I would say it is possible to have occurred exactly as you described (a plasma effect similar to ball lightning); very rare, but not unbelievable at all.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: March 15, 2021, 11:54:49 pm
content: A plasma ball still seems unlikely for the following reasons:A plasma created inside the power strip seems like it would be quenched as it left the tiny exit holes you describe. (That is actually one of the design goals of a good enclosure).A plasma would not tend to follow a parabolic trajectory. A hot ball of ions would be unlikely have its motion dominated by gravity. The necessary magnetic fields to maintain the ball imply really rapid motion of the plasma, possibly in a toroidal vortex. There would be strong interactions between that and the atmosphere (bouyancy, friction, convection ....)Obviously something happened. But I would bet on a jet of molten metal or just hot gases before I went to the plasma ball possibility. When I have been able to reconstruct events like this the initially inexplicable has often turned out to be something relatively mundane. Of course most of the time I haven't been able to make all of the facts fit and just end up scratching my head.

author: coppercone2
author_rank: Super Contributor
timestamp: March 16, 2021, 02:39:16 am
content: it got to like a distance of 4 feet away from, the power strip. its unified because it changed directionI think they have some repulsion properties that's why they can get down chimneys and stuff. I thought it maybe skid in that ground crimp tunnel folded metal crap like a maglev trainit was a unified moving thing because it changed direction like that spiral I drew, it could not have been a jet or lance or something.

author: coppercone2
author_rank: Super Contributor
timestamp: March 16, 2021, 02:45:20 am
content: I don't know if it curved or bounce off the wall, I only noticed it when it was already in flight, roughly across the table but if thats where it came from thats the path it had to take it and it makes sense thats where it came from because it had the blown MOV, the bad smell and the spark noise. The table is like almost pressed up to the wall so it appears decent , just the cables get out with out pinching, the table is a wooden william senoma deal. all the surfaces in that room are either rustic or really worn, nothing in these glinters or shines even right after you wipe the floor, it has a robinson crusoe/ giligans island worn old abraded wood feel (really really mate).the power strip is setup to not get water on it if there is water spilled on the table, it recessed on the table brace 3 inches away from the side.There is nothing else there that can make whatever this is. it is a very relaxing room the blinds are usually half drawn and it has pretty much no reflective surfaces.The bulb is a LED bulb, it is in a glass lamp that is about 1.5 foot tall with a cloth covering around it separated by 8 inches from the bulb to the side of the lamp shade, the clock is a sony dream machine that is working fine. There is no sign of any char on any of those things.I think I am going to consider a whole house transient suppressor because my solar needed to be replaced before, the grid sucks here. I have 3kW of solar

author: Berni
author_rank: Super Contributor
timestamp: March 16, 2021, 06:50:14 am
content: It might still be "welding splatter" but in a way you are not used to seeing it.Lots of things including metals burn in air once hot enough and given a large enough surface area. Some metals burn a lot easier than others and can burn in very different colors of flame. This is also where the color of a lot of high current arcs comes from, its the metal vapor coming off the contacts giving off light in its characteristic color.So the ball you seen might have been a cloud of some metal vapor or dust burning in air. Its perfectly possible the dust is the contents on that MOV. For example a popular component of MOVs is zinc oxide, its possible the high energy event ripped it apart and results in lone zinc ions burning with oxygen. Zinc really loves to burn in air with a bright flame (much like magnesium but not as reactive) and looks nothing like steel burning.Also plasma itself can stick around a bit since it takes time for it to cool down. This can be seen when a large electrical arc is interrupted, it does not go away instantly but it dissolves into fiery flame that drifts apart and fades away.All of this is mostly why multimeters have CAT ratings. You don't want the ball of flame to engulf your arm if such a high energy event happens inside the meter.

author: coppercone2
author_rank: Super Contributor
timestamp: March 16, 2021, 06:52:52 am
content: why does it hold together in a ball though? it was moving like a comet or asteroid or whatever. Ok its like a 0.5cm fire ball that is traveling in the air kinda slow over a 3 or 4 foot arc. It is somewhat like a star pyrotechnic inside of a shell firework, its kind of a unique visual signature.It looked kinda odd though, no smoke trail, not super bright, it was not sputtering or showing effects of burning. I played around with firework chemistry I kinda have a general idea of how these things behave.. maybe it seemed more 'translucent' too, like an alcohol flame.It reminds me more of a welding splatter bead thing for some reason, maybe its because of time, but it was more 'calm' then a pyrotechnic star, those welding beads are kinda like tame. But again the color was doom imp fireball, like a orange/red, not a sodium filled yellow or a white magnesium burn, reminded me more of strontium stuff (like a road flare)

author: Berni
author_rank: Super Contributor
timestamp: March 16, 2021, 06:59:11 am
content: Quote from: coppercone2 on March 16, 2021, 06:52:52 amThe ball can still be a drop of burning molten metal that is skating across the ground much like welding splatter. Except that some metals burn a lot faster and with a brighter flame, making so much light that the whole thing just looks like a ball of light.Good demonstation example of this is magnesium burning:

author: coppercone2
author_rank: Super Contributor
timestamp: March 16, 2021, 07:02:05 am
content: No it did not look like refractory metal fire, it looked like strontium if anything. It was not bright at all like a flash powder or magnesium pyrotechnic composition or magnesium metal burning or titanium sparks. it reminds me of strontium carbonate or nitrate fueled/colored things.I know what you are saying but that is literary like flash bright..Ok if you ever took apart a Rubidium oscillator it reminded me of the type of thing you see in that more then anything. But orange/red. I have a little one that I think I took apart and powered but I am not sure because it was 6 years ago but there is one on mikes electric stuff youtube channel.I keep saying welding because maybe that is what my mind rationalizes "flying red glowing shit' with, but I suppose I am thinking about it now you might be able to say it did not look solid or was some how ethereal.You can color alcohol fire maybe with strontium chloride to do this but if you hurled a cotton ball soaked with alcohol burning red it would not look like this, but maybe more similar.Ok I guess I can say that it was weird and I am having trouble describing it. So maybe atomic clock oscillator physics package without the glass with a different color that of hot steel splatter but some how ethereal traveling through air in a parabolicish arc trajectory.A few days ago I had my hot air station throw some fire balls, they did not look like this phenomena, those were just solder that was in the barrel that got red hot because of max settings and pushed out when I pressed the air. It was NOT a good likelyhood.

author: Cyberdragon
author_rank: Super Contributor
timestamp: March 16, 2021, 07:35:54 am
content: If you take a welder to pure silicon you get a ball lightning like fireball (there are theories that ball lightning comes in several forms, combustion + ions and pure ions with the "shells" as mentioned above, so the term has not been officially applied to any specific plasma formation).Given that MOVs are silicon, did it look anything like these?

author: coppercone2
author_rank: Super Contributor
timestamp: March 16, 2021, 07:51:22 am
content: I think it was less aggressive and more red orange colored, it is not as bright.But maybe it traveled a little bit and cooled off ? if it was the right size, because I did not catch it for the very first part of its travel, but I think if it was ultra bright i would have noticed shadows, then again it was like 3pmBut it was not as dim as a rubidium oscillator that I was comparing it to. I don't know how to explain the ethereal property I am describing, that part makes it different. Ok psychologically when I saw it I thought 'what the fuck is that' "i better look where this lands' but I did not think "OH SHIT ITS SPLATTERING METAL' (which is what I thought when my microwave oven malfunctioned). There was something about it that made meinstead of(because in a microwave its like a lightning storm when the magnetron shorts out)Could it have like a gas cloud around it as it travels maybe?But also the question is, if it go out of the ground hole, how did it get past everything without scorching the brass?Those videos show the correct travel path though I think and how bouncy it is explains how it got out from between the wall and the table maybe.

author: Berni
author_rank: Super Contributor
timestamp: March 16, 2021, 09:04:36 am
content: Yep that looks like the the usual burning ball of molten metal. But it does look rather pretty.Not sure why they behave like that, but i am guessing that the burning is so vigorous that it creates a expanding pocket of gas around it that makes it float and bounce around much like the leidenfrost effect with water on a super hot surface. Eventually all of it burns up and so it looks like it it disappears in thin air.But in can be indeed hard to recall details in a panic moment. I had a cheep chinese PSU module blow up out of the blue and i don't recall what exactly i seen. All i know is that everything went dark because it tripped the breaker, i think there was a loud bang and i think there was a flash but im not sure. Later on i found the glass fuse in that PSU only had the PCB pins remaining, the rest of the fuse was in the form of shrapnel.

author: coppercone2
author_rank: Super Contributor
timestamp: March 17, 2021, 02:17:50 am
content: this happened at like 3pm with home lights off (the room has 4 plane windows with partial blinds) and an open kitchen with 3x window connected to a porch with 4x big glass window,When I came inside the power came back and I only noticed because the refrigerator was off again but the stove was on so I knew something tripped. (stove clock and refrigerator temperature display), the sony clock is hardly noticeable in the day and its set to dim settings.If it was at night its a different story but this room is bright, the blinds are also not metal but just cloth that diffuses light, the kitchen has no blinds either. I only need light when its already almost dark outside. It was also a very nice day save for the wind.The kitchen window that shines into the room is also facing the porch which is semi sealed (it uses grey smoke diffused plastic corrugation for the roof).. so there was no direct sunlight there, its all nicely diffused with white cloth blinds, corrugated porch roof and the windows that shine directly outside only get inside through reflection, and it was some what overcast, enough at least with high clouds that did not really let the sun shine directly.

author: SilverSolder
author_rank: Super Contributor
timestamp: March 17, 2021, 01:17:06 pm
content: Did you hear the thunderclap / lightning strike itself? Or did it happen far away and just propagate?

author: coppercone2
author_rank: Super Contributor
timestamp: March 17, 2021, 07:50:41 pm
content: i heard nothing I thought it was just something happening with the regulation, I assume wind took out tree branches because it was really windy, this is unrelated to any rain, thunder or lightning as far as I know.I don't know what happens I assume they up the voltage because of losses and it shoots up when load is disconnected by a tree?

author: SilverSolder
author_rank: Super Contributor
timestamp: March 17, 2021, 10:05:55 pm
content: Quote from: coppercone2 on March 17, 2021, 07:50:41 pmI guess it's possible to get one heck of an inductive "smack" out of those big transformers, in the right (wrong) circumstances?

author: Berni
author_rank: Super Contributor
timestamp: March 18, 2021, 06:14:55 am
content: Quote from: coppercone2 on March 17, 2021, 07:50:41 pmOver here we run 3 phase with neutral on power poles. So if a tree happens to break the neutral line first then the voltage on the least loaded phase is going to shoot up.But MOVs are known to spontaneously combust here and there. As they experience surges they gradually deteriorate, eventually they deteriorate enough to start conducting slightly at the rated voltage too, making them get hot. Eventually it deteriorates enough where it just start conducting properly at rated voltage, making an enormous amount of power dissipate in them. This makes them smoke, catch fire or explode.

author: coppercone2
author_rank: Super Contributor
timestamp: March 18, 2021, 06:20:37 am
content: 3 power strips and a clock in 1 day is no coincidence, and I don't think they can explode that bad as the picture shows normally? not sure though

author: Berni
author_rank: Super Contributor
timestamp: March 18, 2021, 07:17:59 am
content: Quote from: coppercone2 on March 18, 2021, 06:20:37 amYeah perhaps the quality of the power coming into your house is particularly bad. Try measuring it with a dataloging multimeter.We had undervoltage problems at out house, we didn't really notice since everything worked fine. But then dad got a solar array installed on the roof and every so often the inverter would trip out into error about mains voltage. So i hooked up a multimeter to the phase it was complaining about the most and logged it over a few days. Turns out the mains voltage was sometimes briefly dropping to 180V, but other times was the proper 230V, sometimes staying at 200V for periods etc... Obviously this was not okay, we emailed the plot to the power company, they came around and installed there own dataloger on all of the phases and came to the same conclusion that this is not good. Eventually they came around and we let them run a new underground cable along our property to give this area of the street its own feed from the transformer.Opposite effects can happen with overvoltage if the power company decides to 'fix' such a problem by turning the transformer up to a higher voltage tap. This may get the people on the end of the line the proper voltage but the people close to the transformer might be getting too much. Fast transients can also come trough the lines since they might not get swallowed by the transformer due to inductance at high frequency.But blowing up is an intended mode of operation for a MOV. They are designed to absorb power surges so that they don't blow up something more valuable. If the surge is small enough that might only result in the MOV getting hot from the energy. If the surge is large then the MOV can absorb so much power that it burns up or even explodes, but even then it is still doing its job in turning the energy of the power surge into thermal energy (or light and sound in the extreme cases), this is energy that could have otherwise continued on and blew up a power supply. Just that these large surges physically destroy the MOV so it needs to be replaced.I repaired things before where lightning hit it. I open it up and find the fuse blown and the MOVs looking like charcoal. I place a incandescent lamp across the fuse to see if the thing still works enough to be worth attempting to fix. Sometimes they are shorted or make a fireworks show when voltage is applied. But often it just needs a new fuse and MOVs. They have taken the sacrifice for protecting the rest of the device.