In one-phase system, voltage is distributed over one phase while the other is called "neutral" and should be grounded, AFAIK. But, I think that I have experienced shock when touched one phase in 3-phase system, which does not even have a common ground. Is it charging-recharging of the the body capasistance? Is it less adverse than plugging a person between the phase and ground/neutral? If that is the case then why does the phase gives you the shock but ground does not? I see that birds are fine sitting on the power transmission lines, the high voltage one, I suppose.
If you have a 3 phase star mains system then there is always a common ground ( the to earth connected center on the transformer) and therefore a way of the current to pass from the touched phase trough the body to earth.
In a 3 phase delta mains system there is also a way for the current to pass but this time it is trough the body, the capacitance of the transformer and a different phase on the transformer.
When we have a frequency regulator the above can also take place with the same motivation.
Birds on a HV line can get hurt by lightning because a current can flow from the lightning bolt to the HV line. This in a capacitive sense or when the surge arrester gets activated. Anyway it will kill the bird.
Can 220v touch shock an insulated person?
Insulated from what? If I touch a wire with my finger and another one with my rubber boots, am I insulated or not? Let's try and answer the other questions first.
But, I think that I have experienced shock when touched one phase in 3-phase system, which does not even have a common ground.
As far as I know, there is always a ground wire in every 3-phase system. Closing a loop between touching a live wire and the ground CAN hurt you. If it is a Y connection, a neutral is present as well.
If that is the case then why does the phase gives you the shock but ground does not?
Touching the ground conductor alone does not shock you because the potential difference between the ground and the ground conductor is well... zero!
Same applies if you touch the neutral wire (DO NOT try it though!), as the potential difference between the neutral and the ground wires should be zero, if everything works correctly. In practice, I think it is normal to observe up to a few volts difference, but again, for safety reasons, DO NOT attempt to close a loop between the neutral and the ground using your body!
I see that birds are fine sitting on the power transmission lines, the high voltage one, I suppose.
This is again because the air acts as a very good insulation between the live "high-voltage" wire and the ground. If it is actually very high voltage, birds can get hurt (see how lightning works).
To clarify things a bit more
To get a better idea, in order for current to flow through a conductor, a voltage difference should exist between the end-points. A conductor can be any path of any material, as bad as air or as good as copper.
Because copper has indeed very good conductivity (in simple terms meaning current can pass through very efficiently and easy), we use it to create closed circuits. On the other hand, because air has pretty bad conductivity (or if you prefer, is a good insulator), it is often used in between end-points, where we do not want to create a circuit (as is the space between air wires and the ground).
What I am trying to say here is that anything can act either as a conductor or an insulator, depending on the voltages we are working with in each case.
This is a very impressive example where due to very high voltages, air temporarily acts as a conductor, where normally should be an insulator.