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I'm up to make a 240v breaker circuit for my equipment so the question is 3 prong grounded neutral or 4 prong separate ground??

things to consider
1 almost 90% of the venues where i work have only a 3 prong outlet
2 sometimes i work on generators which have a 4 prong and many times separate grounding is required by the producers
3 sometimes i got to work on a 120v line

any comment,advice or tip will be apreciated thank you

Might want to sub it out to an electrician.

I wonder if our electricity set up is similar to Puerto Rico?

Our normal every day 240V outlet is 10amp active neutral earth.
Some venues have 3 phase (415V) outlets, but the plugs on these vary, depending on the amperage rating. So some are 4 prong and some 5. Is this what you mean? As in making a breakout box utilising the three phases with circuit breakers on each phase, down to regular 10 amp outlets?

I agree with ncgrove, get an electrician to either build you one, or (sometimes a cheaper option)
have him looking over your shoulder while you build one, or check your work.

I'm no electrician, but isn't ground, ground?; meaning, whether it is the 3rd or 3rd and 4th pins, both are able to put current down to the soil. So this means that pins 3 and 4 would simply just be connected together in your box, and the (single phase?) generator would be connected to a big steel peg in the ground.

thanks to all
Here the electrical wiring came from the grid as a single phase 240v grounded neutral which consists of two hot 120v cables and a polarized (neutral) ground. hence the ground is polarized you can divide each hot cable to make two 120v circuits. here you,ll usually find 3 prong 240v 50a outlet for stoves ,dryers or just a high power utility outlet. you can get 240v from the two hot wires. Now what i want is to make 4 separate 120v 20a circuits via breakers wiring etc. (i know how) my issue is if a separate ground is really necessary or just a screw peg to attach a wire from my box to ground when required

Ok that's totally different to here, so I'll but out...

I'd use something like this http://www.thomann.de/gb/hama_stromverteiler.htm There are probably things like this for the 120v world.

Wouldn't go and create my own. Better get it certified. If something gets on fire, or someone gets electrocuted using your kit you will be held responsible if it looks DIY.

With neutral tied to ground at your plug, if a neutral should happen to go open somewhere along the line, you could potentially have line voltage sitting on the chassis of your equipment. In North America, ground or earth is strictly a safety net; it should never have current flow through it, except when a short circuit fault is shunted to ground.

I've seen neutral wires burnt off the buss bar in panels because the X and Y loads weren't balanced.

With this in mind, I would recommend a separate neutral and ground, but ultimately it's dictated by the local electrical code.

the electrical code here indicates that a grounded neutral should be used from the grid to the main electric breaker box and into all 240v outlets (driers ,ac,stoves) but when lowering down the voltage to 120v you should ground the circuit separate from neutral. Older houses (prior to the code update which is back to the 70s) use the metal electric tubbing as ground which is inconsecuent as the breaker box transmits the neutral/ground via the chassis of the breaker box so ground and neutral are joint that way too in the 120v circuit. either way i,ll consult it with an electrician too. in my thoughts i think a separate ground is useless here as it will be at some point connected again to neutral but i also feel the need for a separate ground in a way that it works as a safe discharger

4 prong plug and 4 conductor wire.