The Truth About Solar Storms 91
StartsWithABang (3485481) writes On Wednesday, The Washington Post ran a story about a very large solar flare two years ago that missed Earth, but not by too much. From a scientific point of view, what is it that happens when a solar flare interacts with Earth, and what are the potential dangers to both humans and humanities infrastructure? A very good overview, complete with what you can do — as both an individual and a power company — to minimize the risk and the damage when the big one comes. Unlike asteroids, these events happen every few centuries, and in our age of electronics, would now create a legitimate disaster.
One of many... (Score:3, Interesting)
This is one of many things that causes power outages and loss of communications. In the urban areas, in the cities, people take the stability of the system for granted. Out in rural areas we live with the knowledge that the grid goes down on a regular basis and sometimes stays down for weeks. No power. No phone. No cell phone. No internet. No outside source of water, sewer, emergency services, etc. We make do. We live to survive these events. A solar storm could produce a much more significant event. People in urban areas really need to start being more prepared. The history of stability is very short.
Re:Another ignorant fearmongering article (Score:3, Interesting)
If you've got voltages being induced on your primary wiring much higher than the peak-to-peak of the regular supply, I think you've got much bigger things to worry about.
Telegraph wiring of the 1850s was typically connected to a battery; I imagine that the voltages induced in those long wires was overloading those batteries to the point there were fires. The batteries would have been small: big enough to work the mechanism on the other end for the receiver. Today's loading would be the equivalent of thousands of such batteries; with ordinary resistive loads such as light bulbs and the kitchen stove, multiplied by the number of households having something on, the induced voltage seen at your house should be pretty close to zip.
Re:The failure mode is transformer core saturation (Score:5, Interesting)
... the induced DC from a solar storm isn't as instantaneous as a lightning strike. It takes minutes to develop, which leaves time to disconnect the lines and affected transformers if they are properly monitored.
But ARE they monitored for DC? It's not a usual problem.
Warnings on the order of minutes might be useful if the transmission line were the only one invoved. Unfortunately, the power grid is a GRID. Lots of multiple, parallel, transmission lines, and many, many, more going elsewhere and often creating loops.
Redundancy is a good thing in most situations. But when you have to drop a high line, and don't drop all the others simultaneously, you shift the load onto those that are still connected. When you're cutting off because you're near the limit - either due to heavy load at the time or because of the DC issue - you can drive the others beyond their limits (or throw things out of sync and add a bunch of "reactive current" to the load) and create a cascading failure. (Indeed, this is how the first Great Northeast Blackout occurred: Three of a set of four high-lines crossing the St. Lawrence Seaway near Niagra tripped out, and the redistributed load put one after another generator above its limits, blowing its protective breakers and making it progressively harder on those remaining.)
Gracefully shutting down the grid is not something you do on a couple minutes' notice, even if you have a plan in place.
As I understand, the induced DC is something on the order of hundreds of volts, which is much less than the tens of thousands of volts transmitted across ordinary high voltage transmission lines; disconnecting them should not result in arcing problems across the switches.
First, the problem with the induced near-DC is not the voltage, but the current. Transformers and transmission lines have as little resistance as possible, because it's pure loss of valuable energy. The magnetizing alternating current (i.e. the part of the AC that's there all the time, not just when there's a load) is also limited by the inductance of the transformers, but that doesn't impede the direct current at all. A couple hundred "DC" (very low frequency - fractional cycle per minute) volts, induced for minutes around the loop, can drive a hysterical amount of current.
Once the transformer is saturated, most of the damage comes, not from the direct current, but from the line power, which ends up dissipating lots of energy in the transformer. Meanwhile, at these voltages and currents, the switches that interrupt the AC are largely dependent on the momentary off time as the cycle reverses to quench the arc. If, say, the event happened when the line was running at about half its rated load, the direct current will be higher than the alternating current, so there will be no off time. This can keep the current flowing even through an open breaker (while dissipating megawats IN the breaker). Interrupting DC is MUCH harder than interrupting AC.
Heck, at these voltages even interrupting AC [youtube.com] is hard. (The video is of an interrupter where the jet of arc-suppressing gas failed for one leg.)