I remember here in the United States, I was required to do these ground impedance tests when I installed an underground transformer at the airport, and also a new electrical system at the petting zoo in the city zoo. At the zoo I was able to wet the ground to get a better reading. It was well under the 25 ohm requirement.
They want to make sure if there’s a lightning strike or something, there’s a low resistance path for the current to flow.
This is a picture of how the test was done.
