Directly to ground pole outside drove into ground
Depends what you're trying to protect.
If your goal is to protect the oven from ESD (static electricity) damage or lightning-strike damage, or help it receive radio signals, then going out to a ground spike can help you with that.
It won't do a thing for human safety, though. To protect humans from electric shocks, you can go one of two ways.
You replace the oven's breaker with a 2-pole GFCI breaker. If there's any place to mark this, you mark the oven's outlet with the words
GFCI Protected No Equipment Ground
And then you wire the oven correctly for a 4-wire connection (i.e. remove the neutral-ground strap on the oven) and don't connect ground. If it's a receptacle you fit a 4-prong (NEMA 14) receptacle and do not connect ground and apply the above sticker.
Retrofit a ground
You need a #10 ground wire going back to any of these points:
- The ground bar of the service panel this oven is powered out of
- A junction box of any other circuit with a #10 or larger ground path going back to the panel
- non-flexible metal conduit which is continuous all the way back to the panel
- the Grounding Electrode System, i.e. the bare ground straps between the service panel and the house's grounding electrode(s) - ground rods, metal water main, or Ufer ground.
This wire can be retrofitted as a solitary wire. This wire does not need to follow the same route as the other wires.
If you really, really want to, you can replace the whole 3-wire cable with a 4-wire cable, but that is just a harder way to do the above.
The ground system serves two purposes.
Static Electricity, Lightning and other "Natural" Causes
These types of electricity need to get back to the "source", which is the physical ground (the earth). A ground rod or connecting to a metal pipe that extends into the ground accomplishes this.
Return of current if there is a fault in wiring or equipment
This could include wire damage resulting in a hot wire touching the metal frame of an appliance and many other types of faults. The grounding system provides a low resistance path to get back to the neutral at the main panel to complete the circuit. This is much better than the current going through a person touching the appliance and completing the circuit through their body (NOT a good thing at all). Assuming there is an actual short circuit, the ground path will conduct all the available current so that the circuit breaker will trip. If the only path is the relatively high resistance "physical earth ground", the current may stay well above dangerous levels (it doesn't take much to kill) while staying well below "trip the breaker" levels. FYI, GFCI comes along to provide additional protection in key areas, particularly wet areas like kitchens & bathrooms, because even the smallest ground fault can be dangerous when water is involved because wet skin conducts much better than dry skin.
You need to have both of these protections in place, and normally they are all handled through one set of wires that connects both to the ground (through ground rods or water pipes) and to the neutral at the main panel. Two functions, one combined system, one wire to each appliance or receptacle.
However, I suspect the reason for the question is that you are trying to convert a stove from 3 wire to 4 wire and just don't have a ground wire available and running a new ground wire to the panel is much more work than simply running a wire out to a pole stuck in the ground. The good news is that you can retrofit grounds - i.e., piggyback on another electrical ground elsewhere in the kitchen. There are some constraints regarding minimum wire size, though if you have metal conduit then you may be able to use that as your ground.
Yes under CEI regulation. It's called TT earthing, but in this case you have to protect the stove with RCD (GFI in american words).
That because 'local' ground loop may have resistence high enugh not to let trip an MCB in case of leakage, but high enough to make an imbalance to trip an RCD.
In any case you shouldn't have other masses next to the stove connected to 'another' ground 'on the reach of the user' because, in case of fault, there could be a voltage between the two grounds leaving a potential hazard.
I agree with isherwood, ground in a reference point and it varies from point to point. To be effective the ground in your house needs to be referenced at the same point. There is electrical potential all around us at all times but a difference in voltage is what allows current to flow. If you were to take two points in the earth and measure between them you would get a reading. There are more reasons for proper grounding that are better explained by others as I'm licensed but not really an electrician.