Vertical ground electrode and its diameter

... from the book "Grounding: answers to questions"

Will the grounding resistance reduce at the increase of ground conductor's diameter?
Will the service life of the ground electrode incease at the increase of its diameter?

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Diameter of a vertical ground electrode and its grounding resistance

Two factors have major influence on ground resistance :

soil resistivity (electrical)
electrode length

It can be clearly seen in the formula for calculation of grounding:

formula

Increase of the ground electrode diameter slightly changes soil resistance:

at the increase of the diameter in 2 times, the resistance decreases by 9% of the initial value
at the increase of the diameter in 10 times, the resistance decreases by one third
at the increase of the diameter in 100 times, the resistance decreases slightly more than 2 times (by 60%)

For comparison:

increasing the length of the ground electrode in 2 times, the resistance decreases almost 2 times
increasing the length in 10 times, the resistance decreases by 8 times

Diameter of the vertical ground electrode and its service life

Increasing the service life of a vertical ground electrode primarily depends on its material and protective coating material.

For an electrode made of black steel - an increase of the ground electrode in the diameter, directly affects the increase of service life. The more material in the electrode, the longer it will corrode.

For a steel electrode with zinc coating - ground electrode diameter increase, as in the case of black steel, increases its service life. In addition, the service life will be influenced by the thickness of the zinc coating that is less subject to corrosion than steel: the thicker it is, the longer the electrode will serve.

For a steel electrode with copper coating - the increase of the ground electrode diameter does not affect its service life. It will depend on the thickness of the copper, because corrosion of steel will begin only after the coating is destroyed. Copper is several times less subject to corrosion than zinc - therefore such coating, providing its integrity after installation, is the most qualitative and protects the ground electrode against corrosion the longest (detailed information about this - on a separate page "Copper-bonded electrodes").

However, at the violation of the copper layer to the steel base, due to the occurrence of electrochemical corrosion, the ground electrode will be destroyed within 2-5 years. Therefore, it is very important to comply with all necessary requirements at the manufacture of coppered ground pins, which unfortunately done by not all manufacturers. Tests of such "crafts" in comparison with high-quality products are presented on a separate page "Ground pin".

Useful materials: