petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
Anyone ever have one catch on fire?
exploding surge protector
- Thread starter petersonra
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eHunter
Senior Member
- Location
- North Texas & Georgia
Several. A few of them were high end name brand surge arresting power strips that sacrificed themselves to protect the down stream devices from over voltages.
There was another case where the surge arresting power strips were downstream of a UPS, but the UPS never experienced any damage.
We recreated the conditions in our shop that smoked about a dozen surge power strips that were subjected to the odd shaped stepped wave from a triplite UPS that caused the units to self destruct in a quick flash that let out the magic smoke. It took about 12-15 minutes on the UPS to let the smoke out, but it was repeatable.
I have also seen several whole house units that were smoked due to storm damage and no, they did not protect the electronic items in the house.
weressl
Esteemed Member
Catch on fire not as often as just plain exploding: SOP failure mode. On larger MV units they use strike counters to predict approaching failure and replacement.
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
We had an almost brand new one that failed in the filed last week when the power was turned on for the first time. Just started smoking according to the guy starting it up. Looks like one or two of the 4 MOVs went south.
Maybe just a bad unit.
Maybe just a bad unit.
ron
Senior Member
- Location
- New York, 40.7514,-73.9925
The reason for some recent UL listing product requirement changes are to reduce the frequency of exploding SPD's.
gadfly56
Senior Member
- Location
- New Jersey
- Occupation
- Professional Engineer, Fire & Life Safety
MOV's Do Go "Boom"
MOV's Do Go "Boom"
I haven't had any catch on fire, but I almost had a heart attack in the theater one night. I had an entire 6-dimmer power pack die. It must have been a cascade failure of some kind, because it sound like automatic weapons fire in the lighting booth.
MOV's Do Go "Boom"
I haven't had any catch on fire, but I almost had a heart attack in the theater one night. I had an entire 6-dimmer power pack die. It must have been a cascade failure of some kind, because it sound like automatic weapons fire in the lighting booth.
In the past when I sold these items as I can recall when metal oxide arrestors are applied incorrectly, yes they can fail catastrophically. In selling them into the MV market very close attention must be paid regarding the system L-G voltage where they are normally installed. The ones that I sold consisted a stack of MO disc, sort of like a stack of hockey pucks. If a specific arrestor is installed where the voltage is great enough to cause the arrestor to start shunting current to ground that arrestor can get hotter than a pistol causing the arrestor to essentially explode.
As such it is the potential across the arrestor that cause them to fail if applied incorrectly. If applied correctly they may catastrophically fail depending upon the magnitude of the voltage that they are subjected to.
kbsparky
Senior Member
- Location
- Delmarva, USA
Had a customer lose their neutral on a service feeding a mobile home. They heard POP-POP-POP and the lights flickered and got brighter, etc -- typical of what you would expect when losing the neutral.
Smoke filled the place, and they got the heck out of there, thinking the whole place was about to blow up.
We found the problem ---> overhead messenger wire broken clean off at the top of the pole.
When we restored power, the only thing we could find that sustained any kind of damage was a plug-in surge protected power strip that was fastened to the wall. The surge blew a hole right through the back side of that thing, and IT was the source of all the smoke and smell.
Needless to say, the customer was quite pleased that was the only damage we could find. Everything else worked just fine: Fridge, microwave, lights, TV, etc.
So the el-cheap-o surge power strip took the brunt and saved the day!
Smoke filled the place, and they got the heck out of there, thinking the whole place was about to blow up.
We found the problem ---> overhead messenger wire broken clean off at the top of the pole.
When we restored power, the only thing we could find that sustained any kind of damage was a plug-in surge protected power strip that was fastened to the wall. The surge blew a hole right through the back side of that thing, and IT was the source of all the smoke and smell.
Needless to say, the customer was quite pleased that was the only damage we could find. Everything else worked just fine: Fridge, microwave, lights, TV, etc.
So the el-cheap-o surge power strip took the brunt and saved the day!
kbsparky
Senior Member
- Location
- Delmarva, USA
Not sure if the lady wet her pants on that one, she was visibly shaken, that's for sure.
But they were pleasantly surprised that we could restore power within a couple of hours, and find only minor damage.
Opening the windows for a few hours to air out the bad smoke smell, and they were able to remain in their home.
They were afraid the whole place needed rewiring and they would have to live out of a motel room for several days.
But they were pleasantly surprised that we could restore power within a couple of hours, and find only minor damage.
Opening the windows for a few hours to air out the bad smoke smell, and they were able to remain in their home.
They were afraid the whole place needed rewiring and they would have to live out of a motel room for several days.
I'm somewhat surprised that there more devices fried given that a neutral was lost.
weressl
Esteemed Member
Just that we understand what actually happens.
MOV's do break down a little bit every time they are subject to an overvoltage. The breakdown is proportionate to the experienced voltage AND duration. Eventually the breakdown will reach a level when the MOV will not be able to safely conduct the overvoltage to ground even if it is within it's original rating. Depends on the magnitude and duration of that 'last' fault the MOV will smoke and fizz or exhibit a more violent failure, such as rupture or even overpressure that can be described as explosion. Again this is their normal failure mode.
Circuit breakers can also experience a similar failre mode. Most MCB's are rated to interrupt a fault of their full rating ONCE. That is the UL testing requirement. Nobody CAN tell you what is going to happen in the case of the next full rated fault as the devices are NOT tested for that. Since you would not know WHAT was your fault level, unless there is an upstream wave capture device present, if you suspect a fully rated fault then you should replace the circuit breaker. (So much for CB long-term cost advantage over fuses.) Of course it (almost) never happens in real life.
So a surge protector and a circuit breaker can 'explode' when exposed to it's rated - or even less - voltage or current, respectively. (Of course the argument can be made - and that statement would be more accurate - that when the failure occurs the device is no longer rated for it's original value.)
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- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
Whether a protector "explodes" or not can depend on how the upstream OCPD functions.
For small (i.e. short duration) surges just having the protecto clamp may be enough to reduce the voltage that other loads see without actually tripping an OCPD. In that case the protector has done its job.
For larger surges with a very high voltage and current source, the protector may clamp and trip the OCPD on instant before being damaged itself.
For situations in between, like a lost neutral, the protector may have to break down completely and short out before it can pull enough current to trip an OCPD.
I assume that in the case of the mobile home the main CB opened, and that was what saved the rest of the appliances?
When you have a bike (motor or pedal) accident and your helmet saves your head, most people are not annoyed at having to replace the helmet, no matter how good its condition may appear to be afterward. They need to think of a surge protector the same way.
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weressl
Esteemed Member
Whether a protector "explodes" or not can depend on how the upstream OCPD functions.
For small (i.e. short duration) surges just having the protecto clamp may be enough to reduce the voltage that other loads see without actually tripping an OCPD. In that case the protector has done its job.
For larger surges with a very high voltage and current source, the protector may clamp and trip the OCPD on instant before being damaged itself.
For situations in between, like a lost neutral, the protector may have to break down completely and short out before it can pull enough current to trip an OCPD.
I assume that in the case of the mobile home the main CB opened, and that was what saved the rest of the appliances?
When you have a bike (motor or pedal) accident and your helmet saves your head, most people are not annoyed at having to replace the helmet, no matter how good its condition may appear to be afterward. They need to think of a surge protector the same way.
Just to be clear: surge protectors are designed to protect against high voltage and OCPD's react to high current.
Great point. I picked up on that also. There may be an outside chance that a breaker may trip as a result of the MOVs clearing the voltage surge which may cause a line to ground fault but I highly doubt that would be likely to happen.
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
Absolutely, but if the high voltage is sustained rather then a pulse, the protector will eventually fail, and you can only hope that the fault current through the OCPD has tripped it by then. Once the protector is thoroughly burned out, it can't hold the voltage down any more.
Just like a fuse or breaker has an inverse I T curve, the protector has a maximum energy it can deflect, which is the product of current, voltage and time.
If you are fortunate the I x T that the protector can withstand will be greater than the I x T product that trips the breaker.
A much more common fault, where a protector is expected to be effective, is a very short term surge, like a lightning induced pulse on the line. In those cases, with or without an OCPD, the protector will be able to shunt the surge down to a tolerable voltage. And there is nothing about such an event that, with or without a protector, would trip an OCPD. (Unless some of the loads were forced to act as surge sinks and they failed by shorting!)
The only situation in which they can interact to give complementary protection is the sustained but limited overvoltage, of which a lost neutral is one example.
weressl
Esteemed Member
That is why they call them surge or lightning protectors because they are designed to conduct high voltage surges that have limited energy content - current - to ground to protect equipment exposed to it in which case the equipment insulation would fail. Surges are the results of operational or fault switching. Overvoltage experienced as the result of missing ground of the neutral don't come close to the rating of these devices.
kbsparky
Senior Member
- Location
- Delmarva, USA
Nope. The bulk of the appliances were all connected to the same leg of the incoming service. The surge power strip was connected to the other leg, and took the bulk of the 240 Volt surge. That made it look worse than it actually was, since most of the lights were on the same circuit/leg of the plug-in surge strip.
First thing that I told the customer over the phone to switch off the main.
After the repairs were made, and we restored power, everything worked fine. Even the lights were not burned out.
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