[Editors note: Normally, SurvivalBlog does not usually allow for banter back and forth between contributors of articles and letters, as it has a habit of getting personal and out of hand. However, we will make exceptions when the technical information presented warrants it. Today’s letter is a continuation of the discussion between two such contributors on the effects of NEMP upon metal buildings, and it’s starting to get very technical. If you have a technical bent, enjoy being the fly on the wall.]
When subjected to a rapid increase in an electromagnetic field, the differential in conductivity between steel and zinc is what causes the dielectric effect. Zinc has a conductivity of 106 x 16.6 Siemens per square meter, and steel has only 10.1 x 106. Plus steel has a resistance of roughly 10-8 x 9.9 ohms per square meter, and zinc has a resistance of 6.0 x 10-8. It is this differential in the face of an instantaneous rise off induced current that creates a temporary dielectric effect just as if you had parallel plate capacitors. See this website for a description of parallel plate capacitors.
Also see effects of SGEMP. Key here is the electrons are created on the outside of the structure and must pass to the inside through a layer of greater resistance (speaking of the zinc-steel-zinc layers). Yes, once current flow is established, the author is correct; however, it is in the instantaneous rise of current that is a part of E1 EMP that the problems arise. (A good primer can be found here on the differences between the three types of EMP.)
The author is correct in that normal electric currents won’t cause a dielectric effect. HEMP will. HEMP or nuclear EMP also creates a magnetic field in the earth. See this document for a good starter on the true nature of HEMP or nuclear EMP.
Metal fencing, aka zinc coated steel wire, is a known good collector of nuclear EMP effects. See this document for details. It screams capacitor to me.
Finally, as to grounding, as stated above a nuclear EMP does create a ground magnetic field effect. Grounding, however, is for far more than lightening strikes, as the author stated. Most data centers (and I’ve been running them for close to thirty years now and currently have 167 data centers worldwide that I am responsible for) ground for many more reasons than lightening, aka E2 type EMP. See this document for an idea of what we deal with. Mostly we ground to even out the effects of variances and differentials in any long line, be it electric power, data cables, or even the steel structure of the building.
In short, there is about as much difference between regular electrical concepts and those that deal with the first few nanoseconds of HEMP as there is between regular electrical transmission theory and quantum electrical theory. – H.D.