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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: 0) by Anonymous Coward on Tuesday December 15 2015, @08:45AM
He does have a point in, in some cases.
A firewall usually require two network interfaces. However, you can instead use a managed switch with two VLANs and only one network interface. If you're building your own, a managed switch is a more expensive solution, but when building millions of devices, we're likely talking chips at a few cents a piece. And here's the thing: Most home routers already have a four port switch built in. Except that's at least a five port switch (one port is hard wired to the router), and might as well be a six port one, with the last port used as the uplink port on a separate VLAN, thus saving a network interface.
In this case, switch may very well start out with no VLAN configuration, and only have that loaded when the router starts up (saving a separate memory chip to store switch configuration).
(Score: 2) by frojack on Tuesday December 15 2015, @06:23PM
Except not a single one that I have found works that way.
The WAN port is not physically on the switch group. Separately wired. So just because you can imagine a situation where this might happen doesn't mean this is common or that there is even ONE consumer router that operates that way.
No, you are mistaken. I've always had this sig.