John Doe wrote:
Isn't concrete an insulator??

"The preferred ground in most jurisdictions is a concrete encased grounding
electrode (aka a Ufer Ground, after the inventor's name Herb Ufer).. "

What am I missing here?

Concrete is a conductor, and generally a better conductor than the soil
around it (it's hygroscopic), so rather than the sort of iffy contact
between the rod and soil, you have a much larger contact area between 20
feet of wire and concrete, and an even larger contact surface area
between the concrete and the soil. Run some numbers, and it turns out
that capacitive coupling from concrete to soil is probably lower
impedance than resistance.


There ARE high resistivity concretes (used for things like supporting
rails on electric trains), but that's unusual.

There's lots and lots of field tests, lab work, and theoretical analysis
to back up the consistent good performance of Ufer grounds.