Selective power outage in my house - did the power company do this?

Factual Questions
1

So, it’s officially As Hot as Fuck in Southern California this week, and the local power company, San Diego Gas and Electric, has been asking people to conserve power wherever possible during the day so as not to cause blackouts.

Well, despite that, the power went out today. When it happened, my wife and i were actually just down the street from our place, having lunch with a friend at a restaurant. When the lights went out, we were pretty sure that we’d have no power at home either.

When we reached our building, however, the restaurant downstairs seemed to have power, and when we walked into our place we saw that the ceiling fan was still on. A check of the place revealed that the downstairs TV and entertainment system worked, all the lights worked, and my desktop computer, which i had left running in the second bedroom upstairs, was still on with all my programs and windows open on the screen. The central air also worked.

A closer look, however, revealed that there was no power to the oven, the microwave, or the refrigerator in the kitchen, and there was also none to the washer-dryer combo, which is in an alcove on the same (bottom) floor of the apartment. The other power outlets in the kitchen, however (connected to juicer, blender, toaster, etc.) worked fine.

My first thought was that some circuits had been tripped, but investigation revealed that this was not the case. I went and knocked on the door of one of our neighbors, and they had the same problem: most power working, but large appliances like fridge, oven, and washer-dryer not.

I’m no electricity expert. My only guess was that maybe these appliances are on different voltage outlets, and that the power company has the ability to shut down some type of outlets, and not others. Is that even possible?

Anyway, we went out to the movies, came home a couple of hours later, and everything is now up and running again.

I’ve never seen a case where part of the power in a single place was on, and other parts are off, except in cases of tripped circuit breakers. Anyone know what’s going on here?

2

Your house is fed by three wires, two of which carry AC current from the transformer with a 180-degree phase difference and 240volts between them, and a grounded neutral wire that carries current back to a center-tap on the transformer. If you measure between either hot wire and the neutral you get 120 volts.

You lost of one of those AC current feeds, leaving about half your stuff, plus all 240v appliances not working. This is sometimes due to overloaded wires heating up and sagging until they hit a branch, or sometimes they just get knocked down for other reasons. (If there was a wider blackout, sometimes surge current can cause one of those feeders to break, even if there would not otherwise be a blackout in your immediate area.) In any case, the failure was almost surely localized to your immediate vicinity (e.g. you and your neighbors.) Because anything bigger would entail a failure on the primary side of the transformer which would take down all the power to your house instead of half.

3

We had something like this happen once. I’m no electrician, but here’s what I understood had happened:

If you’re in the US, you likely have a 240v line coming to your house, which is actually two 120v lines in tandem. Not much in your house requires 240v (only some appliances), and the two 120v lines then are split up in your circuit box, each of them supplying power to half of your 120v circuits.

In our case, one of those two “legs” failed, in between the pole and the house. Some of our circuits worked just fine, but anything than ran on 240v, and all of the circuits which were on the failed “leg”, went out.

Edit: ninajed by friedo, who added the bit about the ground line.

4

Recent thread by me.

5

Well, you learn something every day, especially on the SDMB.

Thanks for the answers folks.