Generally, it's transformers and cables failing. PG&E, the main PoCo for Northern CA, was on the verge of bankruptcy after the last power debacle here so they have forestalled a lot of needed replacements and upgrades. As a result, a lot of transformers and cables have been teetering on the edge of capacity for a while now and this heat wave pushed them over the top. I heard from one PG&E friend that in Danville for instance, the little town of 41,000 people next to me, there were 4 transformer fires in 2 days and they hadn't had a single transformer fire in 10 years up until now.
Power consumption throughout all of California was at record highs as well, we came dangerously close to rolling blackouts on Monday and Tuesday of this week.
itsmoked and jraef, why can't/won't the people of NoCA press for the state to allow PG&E be made a publically-held utility? (by public, I don't mean Wall Street, but the customers)
Where I'm at, our publically elected utility board members are always pressing for better reliabilty of utility infrastructure.
Unfortunately, these blackouts provide the practical proof of a wrong old engineering concept stated in the holy books of safety codes and other regulations: that ‘demand coefficient’ or however they call it, which is considered to be 0.7 – 0.9 of the installed power of the feeder. This de-rating of power transformers and circuit breakers is not compensated by a forecast in power consumption that the feeder might be forced to deliver not at the time of its design, but over a period of time that can be considered up to 3 decades. And what’s wrong with the designing data that cover 100% installed power of the feeder? I know, one will say that this de-rating concept saves money; but look, is it a real saving when you purchase two transformers (one that burnt, the other is the replacement) instead of installing from the beginning a transformer that is able to carry the whole load?
Maybe the code experts will rethink the whole dimensioning calculations and allow power system designers to provide data that will be more close to reality.
It is my understanding that utilities often run "small" transformers knowing that someday the transformer will fail due to overloading. In the case of cali's heat wave, I imagine many of the xmfr's finally gave into being overloaded for extended amounts of time. I suppose the risk/reward associated with undersizing xmfr's is very profitable for the utility which is most likely reflected in the user's bill.
It's a political/economic problem just as much as it is an engineerng issue. Politicians deregulated the industry based on the theory that competition would lower prices for customers. To make sure their plan succeeded in this goal, they capped prices at artificially low levels. Now there is no market incentive to invest in new generation or transmission. Thus, the demand exceeds supply.
Go to the San Jose Mercury News web page and look for power outage stuff. (Note: The Mercury is predacious, {business wise}, and keeps harrassing you for personal information so pick the power still out link first!.)
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