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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: 2) by FatPhil on Tuesday December 15 2015, @12:32PM
Absolutely. However, out of paranoia, check everything. The first thing I did when I started house-hunting was to buy a simple mains socket tester. Plug it in, and a pattern of leds lights up telling you what's good and what's wrong. This was after nearly electrocuting myself on some small consumer electronics device on the first day in my previous place - there was god-knows-what coming out of the *earth* connector. Paid a professional to fix that, I'm a wuss.
> 32A raw connections are rare at 220V in domestic scenarios!
Yeah. It's strange that you're not using 3-phase (or 2/3 of 3-phase)? My sauna stove is available in 1-phase 230V configuration at 40A, but I have a 3-phase configuration at 400V and much lower current per phase. Everyone I know (who has a sauna) has the 3-phase install, but that's because in this part of the world saunas are designed in at building/renovation time, not afterthoughts.
Great minds discuss ideas; average minds discuss events; small minds discuss people; the smallest discuss themselves
(Score: 0) by Anonymous Coward on Tuesday December 15 2015, @01:02PM
Those little detectors do not detect hot ground and neutral (sometime happens to defeat the test, I have read). You can use a voltage sensing pen for that.
(Score: 2) by Runaway1956 on Tuesday December 15 2015, @04:33PM
Depending on what part of the country you are in, the electric company may make 3-phase "unavailable" in residential areas. Where I live, there is no 3-phase to the homes. Of course, there is 3-phase at the highway, and if I were to beg and plead, they would come out, run the third wire down the county road, and hook it up to my meter loop. The fee would be as much as several month's electric bills. If I lived in town, or if I lived at the other end of the property, the 3-phase would be a hell of a lot closer, and cheaper, but still not cheap. Different states have different laws, of course. When I was a kid, my dad wanted 3-phase 480 volt, he just picked up the phone, and it was hooked up within a couple days, no problem, no big bill.