Friday, March 16, 2012

Someone doesn't know what they're talking about

OHHhh- it's the NYT!

And the reporter is talking about huge substation transformers.
Transformers are about the size of a one-car garage and usually painted some drab industrial color, but without them, intersecting power lines would be like elevated highways with no interchanges. 
 Ordinary transformers are often too big and heavy to travel by road, and they require special rail cars. But because the transformers typically last 50 years, only a few dozen are shipped each year, so even the appropriate rail cars are in short supply. Ratcheting up the degree of difficulty, many of the places where a replacement transformer might have to go are no longer served by rail.

Not the kind that power your neighborhood, schools or malls.
If those are ordinary transformers, I wonder what he call the square green one sitting in your back yard or on the pole in front of your house?


  1. The "ordinary" (huge) substation transformer is what will get fried by a bad solar storm / CME / nuke EMP. The little ones in the neighborhood substation likely won't fry. Solar storm / CME damage is due to inductive coupling of the magnetic fields generated by the event with the long lines between the big substations. This causes low frequency components in the lines that appear as DC to the transformers, which saturate and are damaged. Transformers don't like direct current much.

    The real problem isn't shipping - it's the fact that there are only a couple factories on this planet capable of making the critters, with that multi-year lead time - and those factories run on electricity.

    Shipping a transformer dry seems like a bit of a risk - the transformer must be bone dry inside and the oil must be perfectly clean, or you risk a brand-new blown transformer.

    1. Worked on them quite a bit over the years; we never had one shipped to our plant dry.

  2. And in Houston that moisture would be a problem with it's 100% humidity.

    How does DCV hurt copper windings on a steel core?
    I thought that since it's not alternating, it would be almost invisible to them.

  3. The DC component causes the iron core to magnetize in one direction - AC switched the core back and forth - this is why the core gets hot, by the way - and in a transformer, there's only so much magnetism you can get before the core saturates.

    When a transformer saturates, the windings don't generate reverse EMF and the current rises dramatically - melting things in the worst case, overheating due to IR losses. Even if the windings don't melt, the insulation gets stressed, and it can arc over internally - dead transformer!

    The CME or EMP could induce a low enough frequency for the transformer to see it as "DC", long enough for damage. It's actually the normal AC component that does the dirty work - the DC just pushes the core far enough along the hysteresis curve to saturate.

    Normally, a transformer is designed to work well away from saturation levels, but as our grid gets loaded ever more heavily, some big transformers are going to be working close to capacity, and it won't take much DC to push them past the limit.


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