I made it with Avasva handbooks !

...THAT YELLOW WIRE LOOKS LIKE A STRIKE WOULD VAPORIZE IT !!!!!!

Here is a good source for grounding info kzfaq.info/get/bejne/hNF0jNOZ1c2co4E.html this will give you AWG TO mm square www.engineeringtoolbox.com/awg-wire-gauge-d_731.html I don't know your code but you should be able to put the ground rod a few cm under ground. We would need to use an 5/8" 8 foot rod, about 1.5 cm and 2 and half meters. keep the soil around it damp if you can, not soaking wet just not dry.. so you did it correct not to go under the panels if you have dry weather. Be safe electricity will kill.

Discover how to do it with Avasva.

It is good practice to keep your ground-rod wire as short as possible, i.e. plant the rod close to the installation. If your panel frame gets struck, the current in the wire will rise so fast that if the wire is too long you will get a side-flash out to nearby conductive material, eg the wires back to the house, or your mppt charge controller etc. Lightning wants to go to earth, whatever route it chooses. The easier you make the path, the more likely it will go the way you want it to go.

Ground connections serve three main purposes, one is to protect you from being electrocuted if you touch something that has a earth leakage, and the second is to protect against the fault currents induced from a lightning strike near your installation. In your case since you're off grid you effectively have a floating mains voltage (I think it's called a IT system in the UK) where none of the phase / neutral is connected to ground so there should not be any earth leakage currents in any of your equipment unless you've tied the neutral to a single earth point in your house which then provides a earth leakage return path if something should go faulty. Have you got any RCD's in your house and have you tested it? The third purpose of a ground connection would be to provide a safe path to ground in case of a direct lightning strike and if that's what you want to mitigate against then you need to beef up the cabling and ground rods a lot as the direct currents from a direct lightning hit are in the thousands of A's so any resistance counts. You would also need spark arrestors on all wires that are exposed to the environment to enable a direct lightning strike to bypass your installation. At lest in the UK you should also put any cables that goes in the ground in conduits or the cable itself should be rated for underground installation, this is mainly to protect against physical damage to the cables in case someone digs in the area. Do you know what the codes are in Spain?

I made it. I used InpliX scripts for that. It was pretty easy to make it

Here is a video that may help you, in respects to grounding. It maybe more than you want, but it is a good resource. kzfaq.info/get/bejne/o9aXdLl2mbvbdqs.html