Where is this Diablo wind, I don't see it. https://earth.nullschool.net/#current/wind/isobaric/500hPa/orthographic=-104.00,41.82,428
Go back a few days! The outages are over for Northern California but the Santa Ana winds may pick up in Southern California.
https://www.sfgate.com/weather/article/PGE-power-shutdown-wind-was-it-a-strong-event-14506572.phpThey weren't thinking this windstorm would be as bad as 2017 but 70 MPH is nothing to laugh at.
PG&E is at the mercy of the weather predictors. If they overstate the windspeed, and they would rather do that than understate it, PG&E has to react.
The utility worries about the wind blowing the lines together or toppling the towers. More likely is the winds blowing trees over or even just large branches across the wires. I think they were predicting winds over 65 MPH.
And no, we can't underground the 500 kV lines. At best, the technology is new and, at worst, it is 25 times as expensive. True, once undergrounded things are a lot better but keeping high voltage in one place is no ease task.
https://www.apnews.com/5fe83d4daed64b5daa67ef5e5d81a936The medium voltage lines could be undergrounded but these usually go to a clients neighborhood of, perhaps, 5 people. Do you really think those customers want to pay the cost of undergrounding? They paid the cost of getting power to their property, it wasn't free, but they certainly won't want to pay to replace what they already have.
Remember, PG&E isn't selling electricity when the customers are dark and they're in the business of selling. They don't like the situation any more than the customers but they simply can't afford to wipe out a few more towns.
The environmentalists make it difficult to cut trees and clear undergrowth. Controlled burns have a way of becoming uncontrolled. And then there is arson. Not every wildfire is PG&E's fault.