The QotD script is run by the cron daemon on panix2.panix.com -- I learned the value of having it execute somewhere outside my house a while ago.
When I woke this morning the power had come back on throughout the house, but then a few minutes later it went out completely and stayed off a while. It came back on again about an hour and a half ago, but I waited until I was sure it was staying up before restarting the computers. As of a few minutes ago, I'm finally back online (my LAN takes a while to get back up correctly, but an insidious typo that makes just enough things work to think the problem is elsewhere doesn't help).
Any idea what happened? With part of the house powered and the rest without, I would be thinking breaker box. But when you said that it all died later and then everything came back on, I couldn't picture a failure mode that account for that...
Only thing I can figure, and I'm not sure what I think I know about power distribution and house wiring is accurate enough for this to be a reasonable guess or not, is that somehow one leg of the 220V line into the house got taken out somewhere upstream of here, and only the three rooms that still had power last night were attached to that leg. (If I understand correctly, the line coming into a house has three wires: two 'hot' wires at 110VAC relative to ground and 180° out of phase with each other so they're 220VAC relative to each other. Any 220V outlets are wired to both 'hot' legs, and each 110V circuit in the house connects to ground ant to one of the hot legs. Um, except that I've got something wrong in that, because in a three-prong 110V outlet, the ground pin is not exactly interchangeable with either of the other two prongs, so I'm confused as to just what the center of the 220V circuit coming into the house is.)
Strikes me as odd that my house is so 'lopsided' in its wiring if that's the case.
Also seems funny that a BGE problem could take out one side of the 220 but not the other, though perhaps that will either make complete sense or sound absolutely laughable to someone who knows more about power generation and distribution.
Actually, the outlets contain ground, neutral, and hot. Both neutral and ground are 0 volts, and are bonded together at the breaker box. But, if your wiring is up to code, they are brought out to the outlets by separate wires. In many areas, the feed is a single phase high voltage drop (for instance, our street is fed by a 7200V 8A supply). This goes to center tapped step down transformers on the poles. The center tap is grounded, providing the split-phase 240V to the house.
Hmmm, All the large mains that I'm dealt with are all three-phase. In addition to stepping down the voltage, the transformers are wired to "hand-out" split-phase 240 balanced across the legs. That makes it easy to drop a 3 phase line into a location.
Of course, then we can start talking about 208 three phase vs... etc. :)
That's "close enough" to truth for dealing with house wiring. Mostly I would add that the power on the street is three phase and you get two of the three phases delivered to the meter base. (That's what is messing with your mental model. Think of it like this:
Pole A B Pole
\ /
\/
+----- Ground
|
|
Pole C
Between any pole and ground you get 110/120 AC single phase Between any two poles you get 220/240 AC (treated as single phase)
It does sound like one of the substation's automatic breakers faulted out and improperly did a partial dump of the load (it should have tripped all three legs). I would guess that when all the power dropped our and then returned was the crew cleaning & resetting the switchgear.
As to how your house wiring is so unbalanced, that usually happens as circuits are added, moved, upgraded, etc. Each electrician figures that the existing wiring as a whole is balanced so his change won't make it to unbalanced. (They're supposed to calculate the load balances at the breaker box each time it could possibly change, but most don't. Indeed, for some the last time they did that calculation was on their license exam...)
Back in the '70s, during the Carter Energy Crisis, most utilities would help homeowners with the costs to have an electrician come out and re-balance their electrical load. (the more balanced the load was across the phases, the more efficient the generating & distribution system could operate.)
Re-balancing the electric load across both phases would also keep you from exceeding the max load on one side.
Janice (Not a licensed electrician so YMMV, etc. But I did study it quite a bit irt HVAC and datacenter applications...)
Technically, neutral is 'ground at the generator', while ground at your outlets Should be a local ground that actually runs to a grounded pipe or pole stuck into the soil nearby. Typical practice is to scrape the paint or oxide from a (metal) cold water supply pipe near where it enters your basement (thus, hopefully therefore in ~nearby contact with damp contiguous soil) and run a wire from there to the ~central ground point of your house.
Ground and neutral are Not supposed to be shorted together in your master breaker box but ~usually are. If they are set up Correctly, there can be a substantial voltage between them. I've seen a 60+ vac differential more than once.
Local ground is Intended to be the dump for Any charge that can't or won't go ~home to the generator as it ~should, via the neutral. Lightning bolts, for example, introduce power into the system that isn't part of the plan and can therefore make a spectacular mess. ;-)
Along with any lightning rods on your roof, the outlets' ground wire is Supposed to go to an actual ground. The more serious ham radio folks and electrical engineers (not to mention commercial antenna testers and such) put a large copper (sometimes plated steel rather than solid) rod into the ground near their building and run a nice heavy copper strap to the ground point of the building.
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When I woke this morning the power had come back on throughout the house, but then a few minutes later it went out completely and stayed off a while. It came back on again about an hour and a half ago, but I waited until I was sure it was staying up before restarting the computers. As of a few minutes ago, I'm finally back online (my LAN takes a while to get back up correctly, but an insidious typo that makes just enough things work to think the problem is elsewhere doesn't help).
(no subject)
Janice
(no subject)
Strikes me as odd that my house is so 'lopsided' in its wiring if that's the case.
Also seems funny that a BGE problem could take out one side of the 220 but not the other, though perhaps that will either make complete sense or sound absolutely laughable to someone who knows more about power generation and distribution.
(no subject)
0 volts, and are bonded together at the breaker box. But, if your wiring is up to code,
they are brought out to the outlets by separate wires. In many areas, the feed is a
single phase high voltage drop (for instance, our street is fed by a 7200V 8A supply).
This goes to center tapped step down transformers on the poles. The center tap is
grounded, providing the split-phase 240V to the house.
(no subject)
Of course, then we can start talking about 208 three phase vs... etc. :)
Janice
(no subject)
Pole A B Pole \ / \/ +----- Ground | | Pole CBetween any pole and ground you get 110/120 AC single phase
Between any two poles you get 220/240 AC (treated as single phase)
It does sound like one of the substation's automatic breakers faulted out and improperly did a partial dump of the load (it should have tripped all three legs). I would guess that when all the power dropped our and then returned was the crew cleaning & resetting the switchgear.
As to how your house wiring is so unbalanced, that usually happens as circuits are added, moved, upgraded, etc. Each electrician figures that the existing wiring as a whole is balanced so his change won't make it to unbalanced. (They're supposed to calculate the load balances at the breaker box each time it could possibly change, but most don't. Indeed, for some the last time they did that calculation was on their license exam...)
Back in the '70s, during the Carter Energy Crisis, most utilities would help homeowners with the costs to have an electrician come out and re-balance their electrical load. (the more balanced the load was across the phases, the more efficient the generating & distribution system could operate.)
Re-balancing the electric load across both phases would also keep you from exceeding the max load on one side.
Janice (Not a licensed electrician so YMMV, etc. But I did study it quite a bit irt HVAC and datacenter applications...)
(no subject)
Ground and neutral are Not supposed to be shorted together in your master breaker box but ~usually are. If they are set up Correctly, there can be a substantial voltage between them. I've seen a 60+ vac differential more than once.
Local ground is Intended to be the dump for Any charge that can't or won't go ~home to the generator as it ~should, via the neutral. Lightning bolts, for example, introduce power into the system that isn't part of the plan and can therefore make a spectacular mess. ;-)
Along with any lightning rods on your roof, the outlets' ground wire is Supposed to go to an actual ground. The more serious ham radio folks and electrical engineers (not to mention commercial antenna testers and such) put a large copper (sometimes plated steel rather than solid) rod into the ground near their building and run a nice heavy copper strap to the ground point of the building.