Ground Grid Rods

If the horizontal electrodes are located below the frost line and the touch and step potential will be limited as required, all season, no need of vertical electrodes- in my opinion, too.

The Authority Having Jurisdiction (AHJ) will stipulate the construction requirements and any periodic testing, if required. For the U.S., most jurisdictions will follow NFPA 70, Article 250, Section III, "Grounding Electrode System and Grounding Electrode Conductor".

You can also find grounding standards in the IEEE NESC-C2, National Electrical Safety Code, Section 9, "Grounding Methods for Electric Supply and Communications Facilities".

Earthing is a very funny thing for you can not rely on the mesh always being low resistance especially in a drought. Installed a mesh earthing system for the construction of a power station and the mesh had to be steel, the earth rods were reo bar welded to the mesh and the jumpers to the tower had to be steel.

Another time while doing earthing on an explosive facility we had to drive copper clad earth rods and each one had to be a few ohms individually and less then 1ohm collectively. Some holes were bored with a rock drill down to 70m and then the earthing conductor was lowered down and the holes were filled with conductive clay. After all a lightning strike on the facility would have led to several hundred tons of Ammonium nitrate make itself felt.

Outside substation fences for a distance of 1m an earth wire was buried and earth rods were driven and the wire was connected to the fence earth as well as the substation earth to maintain a reasonable step potential. To test the substation earth actual AC current was injected into the earth system through a set of electrodes and the current measured from which the earth resistance was calculated. The 4 terminal earth resistance meters were deemed to be of poorer accuracy.

Best practice is to follow the engineered design and tests required. remember a fault can generate many 10 of thousands of amperes and a lightning strike many millions. It had been tested on a lightning strike that after the initial shunt to earth the voltage would rise by 70KV per foot of cable. Remember one flash and your ash!

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NEC Art 250.52 Grounding Electrodes. (A) Electrodes Permitted for Grounding.(4) Ground Ring. A ground ring encircling the building or structure, in direct contact with the earth, consisting of at least 6.0 m (20 ft) of bare copper conductor not smaller than 2 AWG.

IEEE NESC-C2, National Electrical Safety Code. 094. Grounding electrodes. B. Made electrodes.3. Buried wire, strips, or plates. a. Wire:

Bare wires 4 mm (0.162 in) in diameter or larger, conforming to Rule 93E5, buried in earth at a depth not less than 450 mm (18 in) and not less than 30 m (100 ft) total in length, laid approximately straight, constitute an acceptably made electrode.

Site conditions determine that. It's not something an international anonymous Engineering forum can answer.