Science Questions

Can we protect the grid from solar storms?

Tue, 21st Jan 2014

Listen Now    Download as mp3 from the show And now for the weather, in space...

Question

Bill Black, by email asked:

How can we protect power grids from solar storms?

Answer

We put this question to Lucie Green, from University College London (UCL)...

Lucie - Well, we can't stop its impact with the Earth.  That's absolutely certain. Electricity pylonSo, when it arrives, what happens is it encounters the Earth’s magnetic field.

So, these coronal mass ejections are magnetic bubbles themselves in a sense and then they interact with the Earth’s magnetic field.  If you change the Earth’s magnetic field, you can start to create electric currents.

But the national grids, they are interested in the very large events.  There's day to day space weather as I said was sitting in a dynamic and variable atmosphere of the sun. 

But national grid in this country are really interested in the big one that could cause a lot of currents, set up a load of currents that would then affect their electricity networks. 

So, they do take into account what the sun does.  They are watching it all the time. 

What they can do is make sure that there are people at the relevant substations that need to be monitored. 

But they do have ways of bringing up power lines if necessary and monitoring the systems. 

But all of these take time, and this is why we need the forecast, the warning of what's going to arrive at us and whether it’s going to have a strong impact.

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Space weather forecasts will start from the spring of 2014 and are designed to give early warning to private companies and public utilities with critical equipment that is vulnerable to electrical malfunction during a large solar storm . Smith Henry, Thu, 23rd Jan 2014

Space weather induces very low frequency currents in the Earth (almost DC).
This can couple into high-voltage transformers via their earth connection, and cause the transformer to overload, and (in severe cases) burn out.
Some electricity companies have experimented with putting a circuit breaker in the transformer earth lead, so that if these low-frequency currents occur, the transformer continues operating in "floating" mode, and the transformer and power supplies should be protected. evan_au, Sat, 25th Jan 2014

One nice thing about solar flares is that the visible portion travels to Earth in a matter of minutes.  The ion portion which causes the electromagnetic interactions travels over the course of a few days.

If a satellite was placed at the L1 Lagrangian point, it should be able to produce very precise measurements and predictions of the electromagnetic pulse several hours in advance of its arrival to Earth.

I assume a portion of the potential electromagnetic pulse damage is independent of the powered on state of the electronics.  However, one could potentially 100% power down critical items before the pulse hits. CliffordK, Sat, 25th Jan 2014

The damage to transforms arises from the direct current induced by the Solar storm saturating the core and allowing excess current in from the grid.
would be possible to fit capacitors in series with the incoming power line at least in to critical to fail systems. syhprum, Sat, 25th Jan 2014

The crash bang modern films always show the small cylindrical transformers mounted on poles that are such a part of the American scene exploding, what is the typical KVA rating of these transformers ?, to an European the configuration of the system seems rather strange with the centre tap of one of the 220v delta three phase windings grounded to provide two 110v supplies to domestic users.
Would un-grounding this centre tap help the solar storm situation or would dangerously high voltages be fed into the neutral line of domestic users.
(perhaps they would prefer a risk of shocks to losing their power) 
Could the connection be left un-grounded until a modest and safe voltage builds up and then a relay or Zenner diode device could close to bleed the current off. syhprum, Sat, 25th Jan 2014

I'm seeing ratings of the utility transformers between 5 & 1000 KVA or so. 
For a house with 200A, 240V service, that comes up to about 48 KVA, so I would expect the ratings of a transformer to be greater than the 50 KVA for a single house.  A bit less per house if several houses are wired together.

Here, we use essentially 100% electric heat, hot water, etc.  In communities with natural gas heat and hot water, they often have 100A service, and can take lower rating equipment.

A while ago I was experimenting with a solar system.  12V batteries through a transformer to 120VAC, then stepped up to 240VAC.  The problem was that it was difficult to keep the load balanced. 

With a balanced load, one would get 120V on each tap, and 0V coming through the "ground".  With an unbalanced load, I felt it would throw my voltages way out of whack. 

Let's see, it wouldn't work without having at least something on each leg.  But, if the power was different between the two legs, then I felt it would throw the voltages way off, say 1500W on one leg, and 5W on the other leg.  I'm not sure if I tested it, but I felt the lower wattage leg was getting significantly high voltage.

Anyway, I think the answer was to have two independent windings for the two 110V legs.  Everything is typically grounded, both at the transformer, as well as the electrical panel.  Most electrical equipment should work with free-floating power, but it would be complex, and perhaps inadvisable to make an ungrounded electrical system.

In a "main panel", the center leg (white) is wired directly to the ground (bare or green).  Sub panels do separate the two.  But separating the ground would mean replacing every main electrical panel in the country.

One's electrical distribution panel typically has fuses (except the Neutral/Ground side).  The utility company also has some fuses in their lines.  If one had isolation breakers or fuses for every transformer, then would one just need to reset or replace the fuses?  Replacing a hundred million fuses across the country would be a pain, but possible in a few days. CliffordK, Sat, 25th Jan 2014

When I was fixing TV,s for living I came across one case where the neutral line had failed on the three phase star connected 415/240v domestic system so that the voltages varied wildly as people switched different loads on, I broke the rules and connected the neutral to ground to avoid the TV getting destroyed. syhprum, Sat, 25th Jan 2014

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