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Comment: The failure mode is transformer core saturation. (Score 1) 30

by Ungrounded Lightning (#47536253) Attached to: The Truth About Solar Storms

High induced votlages in open wires are a problem, but they're not the big one.

The biggie is common-mode currents in long high-voltage transmission lines adding a strong DC component to the current in the substation transformer windings - high enough that when the same-direction peak of the AC's cycle adds to it, the core saturates. Then the inductance of the transformer drops to the air-core value and no longer substantially impeeds the current.

The current skyrockets. The resistive heating of the windings (and the force on the wires from the magnetic fields) goes up with the SQUARE of the current. The windings quickly soften, distort, form shorted turns, melt, open, short out to the frame, etc. The transformer is destroyed, or committed to a self-destructive progressive failure, in just a handful of such cycles - too fast for the circuit breakers to save them (even if they DO manage to extinguish the arcs with the substantial DC component to the current.) Even if the transformer doesn't explode and throw molten metal, gigawatt sustained arcs, and burning oil (or burning-hot oil replacement) all over the substation area, it's still dead.

This happens to MANY of the giant transformers in the power grid. Each set of three transformers that has one or more failed members means a high-voltage transmission line that is shut down until the transformer is replaced.

There are essentially no spares - these are built to order. Building one takes weeks, and there are few "production lines" so little parallelism is available. What is destroyed overnight will take years to replace, while each intercity power transmission line is not functioning until the transformers at its end ARE replaced.

The current occurs because the transformers are organized in a "Y" arrangement, and the center of the Y is grounded at each end (to prevent OTHER problems). The transformers have enough extra current handling capacity to avoid saturation from the DC through that center connection to/from ground from ordinary electrical and solar storms - just not a giant one like we get every couple centuries.

The solution is to put a resistor in that ground connection, to limit the DC in the lines (and dissipate the energy it represents). Indeed, a few lines have such resistors already.

But a suitable resistor is a box about the size of one of the transformers. It's very expensive. And it only makes a substantial difference to the operation of the lines in such a once-in-centuries event. So most executives don't spend the money (and get dinged for costing the company millions) to put them in, to prevent a failure mode that hasn't happened in the generations since Tesla and Westinghouse invented the three-phase long-line power grid.

Or at least they don't until the regulators or their stockholders require it. Which means said decision-makers need a little educational push to decide it's worth the cost and get it done.

Thus articles like this. B-)

Comment: Re:But what IS the point they're making? (Score 1) 240

That's the sound of you missing the point. TFS goes into great detail about facts of whats happened, then says "which makes the point" - but it never MAKES the point. It's just a groupthink argument that everyone must somehow naturally arrive at the same conclusion.

Comment: Re:Bullshit (Score 4, Informative) 168

I live in Florida. Yesterday I had to call the Florida Department of Highway Safety and Motor Vehicles. All I had to do was wait for the option to press '1' for spanish to expire and I was connected immediately to a real person who answered my slightly complicated question easily, clearly and quickly.

I also own a business (and have owned two) in Florida, and every time I've had to deal with the Florida Department of Revenue (sometimes I got busy and forgot to pay my sales taxes) they have been friendly and helpful.

I wish, wish Cox Cable had the kind of friendly and expedient service Florida's government entities do.

Comment: Re: name and location tweeted... (Score 3, Interesting) 785

I'm wondering a little differently. I wonder how plugged in that gate representative must of been to find and successfully identify the source of the tweet and call the family off the plane before it left.

I say this because I don't see some SWA social media monitoring department demanding the tweet be removed in that fashion. I figure it was the 'dissed' gate rep herself that did it.

Real Users find the one combination of bizarre input values that shuts down the system for days.