sunspots and power failures urban legend or for real?

They can cause large DC currents to flow in long-range AC power lines, tripping breakers and causing all sorts of interesting effects.

It's more a thing that you need to maintain the grid against than something (like a truck running into a power pole) that just takes things down no matter what.

It doesn't just pop out in a web search, but there is some information out there -- you may be able to find a credible report with numbers.

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re

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Google helps

-- Bill Sloman, Nijmegen

The Sun has a large magnetic field. We also orbit inside the Sun's atmosphere which consists of fast moving charged particles. The Earth-Sun system is a dynamo inducing huge ground currents (as in, in the ground), as well as other currents in the sky like aurora borealis.

Quebec is more vulnerable than some due to the enormous distances involved in our grid.

It's not so much the sunspots, directly. It's the solar flares that come along with them.

In summary (definitely oversimplified and not 100% literally accurate): sunspots are the surface manifestation of a complex knotting of magnetic fields on, above, and under the visible surface of the sun. These magnetic fields can store an incredible amount of energy. They're powered by the flow of currents within the sun, and by the differential rotation of the sun's gas/plasma body (e.g. the parts of the sun near its poles rotate with a different period than its equator).

Periodically, different sections of the fields break and recombine, releasing some of the magnetic energy in the form of a solar flare (with "some of the magnetic energy" being measured in units of Really Big Hydrogen Bombs).

The flare superheats portions of the sun's atmosphere (causing a burst of ultraviolet and X radiation that we can detect), and accelerates part of the sun's atmosphere outwards (a "coronal mass ejection"). The radiation travels at the speed of light, the CME travels rather more slowly (and takes several days to reach the Earth's orbit).

The ejected solar atmosphere consists largely of plasma - protons and electrons. When it approaches the Earth, it runs into the Earth's magnetosphere (the portions of the magnetic field) and the charged particles are channeled by the Earth's magnetic field, flowing down the magnetic field lines towards the North and South magnetic poles.

The results are striking. The particles themselves can ionize atoms in the upper atmosphere, creating auroras visible far towards the equator. And, the heavy flow of charged particles creates large-scale magnetic fields, which then induce currents into conductors on the Earth's surface below.

These induced currents (low-frequency, sometimes approaching DC) are the thing which cause damage to power distribution networks.

The most famous example I know of in recent history took place in

1989... it resulted in damage to and shutdown of the electrical grid throughout much of eastern Canada. Damage is estimated at hundreds of millions of dollars. For details, see

There was an even bigger solar storm in 1859 - by report it was so strong that the induced currents caused arcing of long-distance telegraph lines, and actually allowed telegraph operators to operate their telegraphs with no battery connected at all. If an 1859-level solar storm were to occur today... well, the results would be messy. The surge currents can burn out the high-voltage distribution transformers and voltage converters used for the long-distance electrical grid... and the time to build new ones and replace the damaged hardware could run into months.

See

for mention of the 1859 storm.

There are plenty of other articles findable via Google on both of these solar storms.

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Why not look it up. Google is your friend.

You are asking about coronal mass ejections. A bunch of dense solar plasma hitting the Earth's magnetic field deforms it and induces huge currents in the long wires of the national grid at high latitudes.

You also get very pretty auroral displays visible at latitudes well away from the poles for the strongest solar storms.

You can get alerts when it is worth watching for aurora at your location

Regards, Martin Brown

Though there's an importance difference, in that trucks into power pole accidents tend not to be correlated with other similar issues. Whereas having transmission lines fail at the same time due to solar effects can easily destabilise the network, and lead to widespread outages.

Sylvia.

are

a

thanks for that link...this section seems most relevent to my question...

"=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D from Wikipedia Electric power When magnetic fields move about in the vicinity of a conductor such as a wire, a geomagnetically induced current is produced into the conductor. This happens on a grand scale during geomagnetic storms (the same mechanism also influences telephone and telegraph lines, see above). Power companies transmit alternating current to their customers via long transmission lines. The nearly direct currents induced in these lines from geomagnetic storms are harmful to electrical transmission equipment, especially to the transformers=97it overheats their coils and causes saturation of their cores, constraining their performance; it also tends to trip various protective devices. Potentially the heat generated in the iron cores of the generators can destroy them and chain reaction could blow transformers throughout a system[7]. On March 13, 1989, in Qu=E9bec, 6 million people were without commercial electric power for 9 hours as a result of a huge geomagnetic storm. Some areas in the northeastern U.S. and in Sweden also lost power. By receiving geomagnetic storm alerts and warnings, power companies can minimize damage and power outages. =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D"

So the sun spots or magentic storm induce a ****DC CURRENT**** into the power lines and the xformer cores tend to saturate... makes sense... and the saftyies trip causing a power failure..

so thinking about how much DC current gets induced on a line and how much DC current it takes to bother a power xofrmer...

From experience with smaller xformers I know a small amount of DC VOLTAGE on a xformer can be very bad becasue the DC current will increase limited only the the DC resistance... but it sounds like these magnetic induced currents are more like current sources rather than voltage sources. I would guess an xformer could handle an additional DC current from a current source as long as the combination of AC current and DC current did not exceed the flux limitation.

OK So now it is starting to make sene, the flux swing in the core is a function of the primary applied AC voltage and not (to first order) the secondary load. So if the xformer is designed for a certain primary AC voltage and that uses up say 90% of the available flux swing.... and then this extra DC current comes along and is say only

10% of the AC current, then all of the sudden the core is near saturation... the only way to prevent this if you knew a storm was coming is to reduce the AC VOLTAGE applied.. it does no good to reduce the load..

OK interesting... so the key point is that the AC grid is intolerante of relativly small additional DC currents due to the small margin to core saturation for efficent xformer design..

sort of ties into the microwave oven xformer thread...

thanks

Mark

Yeah but it's probably a common mode current, ie, same current in both wires.

OK So now it is starting to make sene, the flux swing in the core is a function of the primary applied AC voltage and not (to first order) the secondary load. So if the xformer is designed for a certain primary AC voltage and that uses up say 90% of the available flux swing.... and then this extra DC current comes along and is say only 10% of the AC current, then all of the sudden the core is near saturation... the only way to prevent this if you knew a storm was coming is to reduce the AC VOLTAGE applied.. it does no good to reduce the load..

Unfortunately some loads will draw more current with less applied voltage. Usually things like motors, switching power supplies, and similar devices that draw whatever power they need to drive the load.

I wonder how this induced DC current affects DC transmission lines? It could possibly add to or detract from the current already flowing. I suppose it could cause a voltage surge that exceeds the ratings of the thyristors used to convert from and to AC.

Paul