New service, detached structure
You are best picking one Code and following it religiously.   It looks like Ecuador is in the North American system of 120V on small circuits served as 240V/120V split-phase. So use American or Canadian code. 

Any house in the United States gets only 3 wires from the power company and down the weatherhead: 2 hots and neutral. Typical weatherhead:



Note above that the bare weight-carrying cable is also carrying neutral.  That is an idiom only the power company gets away with. 

Each house derives its own ground with ground rods or water pipe bonds or both.  And then, ground is bonded to neutral in the main panel only.  From there to all other points, neutral and ground are carried separately.   Go 8' on the copper bar, and use 2 of them at least 6' apart.  On an outbuilding you would also need a grounding system bonded to the ground bus.  That does not substitute for a wired ground, that is still needed. Dirt is not a good conductor. 

That brings you into conformance with USA practice.  

The main panel being defined as the panel where power comes in from the utility. If the power company provisions power to two of your buildings, you have two services.  Don't mix them.

Wire from a main panel to a subpanel in an outbuilding must be 4-wire (hot-hot-neutral-ground). If you only need 120V devices, you can omit a "hot".  Generally we bury lines between buildings, but if you go overhead, your bare/carrier wire can't be hot or neutral, those must be insulated.