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posted by martyb on Tuesday December 15 2015, @04:18AM   Printer-friendly
from the blackouts-and-brownouts dept.

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?


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  • (Score: 2) by sjwt on Tuesday December 15 2015, @10:51AM

    by sjwt (2826) on Tuesday December 15 2015, @10:51AM (#276593)
    Starting Score:    1  point
    Karma-Bonus Modifier   +1  

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  • (Score: 0) by Anonymous Coward on Tuesday December 15 2015, @02:44PM

    by Anonymous Coward on Tuesday December 15 2015, @02:44PM (#276658)

    wikipedia is a bit low on "brownout".

    i happen to have a bog normal 50Hz ~220V/380V three-phase four-wire connection to a Y-transformer.
    Were i live we don't have many small powerplants but rather a big lignite burner that has to service a rather
    big physical area (of course it is interconnected to other power plants in the country).

    sometimes we get "brownouts"; that is one phase is at about 217 V while the other ones could be ~76 V and ~117 volts or so.
    during one of these brownouts i had to do some errands and passed the "service bus" of the electrical power provider
    and they were replacing (again) a fuse on the medium 22kV lines going to my area.
    the 22kV fuse blew on one phase and so the transformer was only fed by two-phases from the 22kV side and then, because it was a transformer,
    it transformed some of the working phases onto the "dead" phase but only yielding 76 V or 117 Volts or such.

    so if a supplying phase on 22kV breaks a fuse then you get a brownout also.

    btw, asking the repairmen about the amp rating for the (massive) 22kV they told me it was 12 Amps ^_^
    i guess they cannot put a bigger fuse because else the 22kV lines would need to be replaced or else start sagging and/or over-heating.