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Our power went down yesterday afternoon (December 12). The utility posted a message on their 1-800 number with expected repair time (a few hours later), but no explanation except that ~2000 customers were affected in our suburban area (Northeast USA).
Here's the weird bit -- LED bulbs stayed on, at reduced brightness. I got out a meter and measured 16 VAC in the house. This was enough to make useful light from "dimmable" LED bulbs (happened to be GE brand). After it got dark, we could also see that incandescent bulbs were giving off a faint reddish glow.
16VAC was also enough to keep a Netgear home router/Wi-Fi box going, it must have a switcher in the wall wart that accepts a really wide input voltage range?
Called a friend on the other side of the country who is an EE (with hardware background). He didn't have a good explanation, but suggested that in the process of bringing the grid back up there might be some big voltage swings--recommended unplugging everything we could. Went out to dinner and all was restored when we got home (no damage).
He also told a story from a rural area (near CA-Nevada border) where there was a power failure that upset the normally-balanced split phase -- instead of ~120V on both sides of neutral, the power went to 80V on one side and 160V on the other side of neutral. Equipment on the high voltage side failed due to extended over-voltage, seems that surge suppressors won't deal with this much energy.
Anyone? How does the grid fail-soft?
(Score: 4, Informative) by Some call me Tim on Tuesday December 15 2015, @04:47AM
Consumer grade surge suppressors aren't designed to handle extended over voltage loads. They shunt to ground momentary spikes from 330Vac (UL listed devices) and up for very brief amounts of time. The components (MOV's) will also degrade after a number of spikes and then you lose all protection. https://en.wikipedia.org/wiki/Varistor [wikipedia.org]
Questioning science is how you do science!
(Score: 0) by Anonymous Coward on Tuesday December 15 2015, @05:00AM
> The components (MOV's) will also degrade after a number of spikes and then you lose all protection.
The good surge suppressors will "fail dead" - once the MOVs are burnt out the power-strip will stop working. Some go permanently dead, others act sort of like a circuit breaker and you can turn them back on and use them as a plain old power strip. The shitty ones just keep working even though all the suppression has been burnt out.
(Score: 0) by Anonymous Coward on Tuesday December 15 2015, @06:58AM
once the MOVs are burnt out[,] the power-strip will stop working
A metal-oxide varistor used as a surge suppressor is a -shunt- device.
It would be interesting to know how the failure of that (typically getting higher in resistance and breakover voltage with age) disables the strip.
I suppose that they could specify the device so that it is *always* pulling some current and, when that current falls below a threshold, additional circuitry could cause a relay to drop out.
That kind of spec would be really non-standard and the protection device would consequently have a shorter lifespan.
-- gewg_
(Score: 0) by Anonymous Coward on Tuesday December 15 2015, @12:42PM
You can have a computer chip count the number of power spikes, then assume the Varistor is damaged after some limit (they are rated by the number of joules after all).
I have a fairly expensive one that promises to beep annoyingly when the protection runs out. Not sure if I think that is a good thing or not... It also has a low-pass filter that will filter the smaller spikes.
(Score: 2) by el_oscuro on Wednesday December 16 2015, @12:08AM
That's true. A number of years ago, I was TDY to London and had to setup US spec computer equipment. So we had transformers to convert the 220 to 120. Part of our setup process involved testing of all of the components prior to use. It was an important event and our shit had to work.
So I plugged in the transformer, plugged the laptop in, and booted into the DOS application we ran. Our laptops were the heavy duty Grid Compasses with titanium cases. Anyway, it ran fine, so I shut it down and plugged in the surge protector...
... Which promptly exploded. We ran a voltage check on the transformers output and instead of the expected 120V it was putting out almost 400V. I guess I should have tried the surge protector before the laptop, but I had never seen one explode before.
I guess they don't make computer equipment like they used to.
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