I recently had a power surge at my house, and some devices on my surge protectors died (graphics card, tv, modem) but others were fine (router, xbox, apple tv). I don’t understand what the difference was, can surge protectors be explained more on how they work?
In: Technology
It would be odd for a device to be behind a protector and have that device die from a surge while other devices are protected. Generally a protector does a more “all or nothing” kind of deal.
On the other hand, with some protectors not all outlets are actually protected. It would be much more common to plug 6 devices into a protector and only have 3 protected outlets. That’s not uncommon.
But having said all that, your protector may have entirely failed and some devices were killed by the surge while others were not. Some devices are just more robust than others, and there’s a component of luck here as well. I once had a surge kill a fridge, but the TV (plugged into the other plug in the same outlet) was fine.
It’s also worth noting that it’s not only electrical lines that can carry a power surge. Basiclly any conductive line that goes outside could transmit a power surge, things like cable lines sometimes can kill a cable modem and have that modem send the surge down the ethernet cables and have it kill a PC.
In this case it’s odd that the Modem died but the router didn’t. So likely not that.
The ones I’m familiar with work by opening a path to ground during overvoltage events. These need to be on a grounded circuit to work, which newer homes are. They can also wear out over time or be damaged/consumed during an event and no longer perform their intended duty.
That’s said if the surge was caused by something very energetic affecting the power grid your surge protector could have been insufficient to cope. Perhaps some of the electronics absorbed the energy and protected others or were just more sensitive.
Surge protectors are filled with small components called MOVs. These components can absorb a certain amount of electrical energy before they die, which should stop the flow of electricity. Additionally, these devices have a time parameter, meaning that a small amount of high voltage will get through them before they are fast enough to react to the high voltage. This high voltage can then affect your other electrical devices. Finally, over time, small spikes in power, which you often will fail to see, can add up with these MOVs. A dozen small surges can add up to one large surge. This is why many surge protectors suggest that you replace them every few years
Next, these surge protectors normally only protect your electrical lines. Phone lines, cable lines, etc. can all be conductors for lightning strikes and power spikes. When I worked in retail computer sales back in the 90’s, we would sell dozens of new dial-up phone modems after every thunderstorm. Your cable modem likely died due to incoming spikes from the cable line. Likewise with the TV. And graphics cards tend to be very sensitive to incoming power.
From an electrical perspective, any time you have two devices in parallel they will have an equal potential (voltage) across them. So if you have a printer, PC and LED light all plugged into a power strip (i.e., in parallel), they all have the same voltage 120v across them.
But if a jumper is placed in the last slot of the power strip, you have a direct short also in parallel. If the jumper is zero impedance, then by Ohms Law, there will be no voltage drop across it. So by Ohms Law, the other devices in parallel (the printer, PC, LED) will also have zero voltage across them. The jumper has effectively collapsed the voltage across your devices and source voltage is dropped internally in the source itself and the accompanying wires. Kirchoffs 2nd Law.
An arrester is basically a jumper that is voltage activated. It sits in parallel with your devices and appears electrically as an open (high impedance) circuit under normal voltage conditions. But they have a voltage threshold (often around 330 volts) where the impedance collapses and they become a short instead of an open. That in turn collapses the voltage across across any device in parallel with it. When the high voltage is removed, the arrester becomes a high impedance device again and the circuit is back to normal.
That’s the theory.
In reality, the arrester (normally a metal oxide varistor (MOV) or something similar) doesn’t go to zero impedance, so there is always some voltage drop still present. Also, the arrester has to have the capacity to survive being a short circuit for the brief length of time it is acting as such. This capacity is expressed in either amps, Joules, or both.
So in answer to your question, the voltage across all the devices is mitigated to some extent, but not entirely, and at that point whether they survive or not is more a matter of their individual protection and robustness. Having one device survive a surge while another dies is very common.
They are NOT an over voltage device; they are a surge/spike protector. In other words, a condition lasting milliseconds if not microseconds. A sustained over voltage, like from a bad transformer, will simply destroy it if it exceeds its voltage rating.
There are a multitude of sources for surges, not only lightning. Utility device operations are a constant source (breaker operations, capacitor bank switching, etc.) and while they are usually of longer duration, they are usually lower energy. Anyone thinking these are infrequent occurrences has never seen an isokeraunic map.
[https://hazards.fema.gov/nri/lightning](https://hazards.fema.gov/nri/lightning)
Bottom line. You are not aware of most surges.
An arrester is like a seat belt. A dog runs in front of your car, you hit the brakes and the shoulder strap goes tight. No blood, no foul. Then someone hits you going 30 mph in an intersection. You may have a bruise, but you didn’t lose your teeth on the steering wheel.
But if you hit a semi going 70 mph head on, you’re dead.
Arresters are the same way. If lightning hits your house, it won’t matter if you have an arrester or not. But if it hits a block away, you might be fine. And most do. And as noted, you probably aren’t even aware of most surges.
The basic answer is, most things we call surge protectors are kinda crap and aren’t very good at that job. As to why some things fail, but not everything does. That’s mainly just chance. A power surge isn’t a guaranteed death sentence, especially since there can be different severities of surges.
My advice to you is to get a UPS for your most expensive equipment.
Sounds like you might have both a Surge Protector and an Uninterruptible Power Supply (UPS). Typically Surge Protectors only suppress surges of power coming in over the power lines. UPSs have a built in battery as well as a surge protector so it can maintain power to the devices in the event of a power failure.
Routine is for a plug-in protector to earth a surge destructively via any nearby appliance. An IEEE brochure demonstrated it. A plug-in protector in one room earthed a surge 8,000 volts destructively through a TV in an adjacent room. That made obvious if others bothered to first learn what a plug-in protector does.
A 5,000 volt surge is incoming on the hot wire. That surge connects unimpeded into all nearby appliances on each hot wire. That protector has a let-through voltage; typically 330. Now 4,670 volts is also incoming on each neutral and safety ground wires. Where is the protection? In profit margins.
Surges do damage by hunting for an appliance that makes a best connection to earth. Some devices made that best connection destructively. So that surge need not flow through a dishwasher, clock radios, furnace, LED and CFL bulbs, refrigerator, GFCIs, garage door opener, recharging electronics, door bell, stove, central air, or smoke detectors … this time. Details in paragraph 11.
It is electricity. It only does damage when it has an incoming and a completely different outgoing path. Damage is often on the outgoing path.
If one does not properly earth ground a Type 1 or Type 2 protector, then that surge is inside hunting for earth ground. That connection to earthing electrodes must be low impedance (ie less than 10 feet). Only effective protectors are allowed to make that connection. If a Type 3 (plug-in) protector was earthed, then even an electrical code violation exists.
Did they forget to mention all this when selling a $3 power strip with five cent protector parts for $25 or $80? Of course. They know which consumers are easy marks.
Honesty only exists when numbers say why and how much. Effective protector (for about $1 per appliance) means *hundreds of thousands of joules* (a surge) dissipates harmlessly outside. Then a surge is **nowhere** inside. Then best protect at an appliance, already inside all appliances, is not overwhelmed.
Effective protectors are not promoted by a massive disinformation campaign. Effective protectors do what Franklin demonstrated over 250 years ago. These devices were routine all over the world over 100 years ago. In all facilities that could not have damage.
Then scammers discovered a market of the most naive consumers. Who do not always demand facts with numbers. Then spend $25 or $80 on a $3 power strip with five cent protector parts.
Incoming surge on AC mains. Since those wires have no effective protection. Hunting for earth ground.
TV cable is required to have best protection earthed for free. That is done without any protector. So that TV cable was a best outgoing path, destructively via a router, Xbox, Apple TV, etc.
Nothing new. [All professionals](https://www.reddit.com/r/audiophile/comments/195guja/online_ups_vs_power_conditioner_vs_surge/khz6k9h/) have long been stating reality. Since reality is never found in a tweet, then many cannot read it.
In your case, [this AT&T discussion](https://coderanch.com/t/601307/Lightning-protection-PSTN-line#2744140) probably defines everything.
Most of what was posted here is disinformation. Since most do not like to learn they were easily duped, then many will only downvote. Rather than ask questions to learn more. Or a science well proven all over the world even over 100 years ago.
No low impedance (ie less than 10 foot) connection to earth ground electrodes means NO protection. Made obvious by what was first taught in elementary school science. That simple.
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