When normal electric is generated you have a star point and that is grounded thus u get your neutral off that point you dont just get a neitral from anywhere its earthed???
The first thing you need to appreciate
properly is the difference between Neutral (N) and Earth (E)
Earth is the conductor that provides a low-impedance path to the Earth (i.e. the body of the planet) to prevent hazardous voltages from appearing on anything you might touch... It's the 'fault condition' return path if you like.
Neutral is the circuit conductor that
normally carries current back to the source. - The
normal return path.
So, for example, in a normal household setup we (hopefully) have a device that monitors the 'balance between live and neutral currents on a 'what goes in must come out' basis; any imbalance means that current is returning to its source via the protective earth (rather than neutral) - which means something's gone wrong! - And in these circumstances we want to quickly isolate both live and neutral paths.
You will, I hope, appreciate the need for RCDs - ELCBs GFi's however you fancy calling them? And have an idea that's (roughly) what they do? - And hopefully the penny will begin to drop that beyond the RCD, neutral and earth are two different things; even though they might be physically linked elsewhere in the greater scheme of things?
So far so good?
Now... 'When you generate electric'
you might or might not have three 'generator coils' in the machine. So, let's think of a single coil generator for now rather than confuse things thinking about three-phase...
Thinking about the solitary output winding...
As the machine (generator) goes through it's cycle one 'leg' of the coil 'pushes' current while the other end 'puls' it back it, and vice versa as the thing goes round. Thus;
neither leg can be said to be inherently either live or neutral - In fact, what's delivered to homes on the U.S. system is almost-precisely that... They actually get two 'hot' wires fed to the house which measure 240v across these connections called L1 and L2. Not everything in the US runs on 120V! (Not to get too bogged down - I'll gloss over the vagueries of the American system, it's centre-tapped neutral etc and how the 120v is derived etc...)
Let's get back to the simple single-coil generator... as others have suggested, neither L1 nor L2 are 'inherently' neutral conductors they are opposite ends
of the same phase.
Following me so far?
Let's go back to your picture of "When normal electric is generated" or more accurately when 'normal' electricity is dropped via the distribution transformer down to 240V (or so) to be fed as a single live wire to your home...
The three SECONDARIES of the transformer (up a stick in a field or hidden away somewhere in a small building) are indeed each connected at one end to a common star point... Which is then neutral
relative to the three phases. - As we only want only one phase to our house, to get power to us we need to be 'sent' the
neutral and the phase.
Now... Hopefully it's becoming clearer that in this situation there is no inherent reason for there to be a relationship between neutral and earth. One useful way to think of this (although its strictly-speaking incorrect) is that the live wire is the 'send' and the neutral is the 'return'.
There are a few practical and safety issues with that though.
Because there is no relationship between Neutral and Earth it's possible for there to be a significant potential difference between them! ...Which, should you become the conductor in the earth-neutral path can be really quite distressing.
In normal distribution, it's both convenient and safer to tie neutral to earth at the transformer (power station if you like).
Because, by this means, you've forced a relationship between neutral and earth it therefore becomes possible (and common) to 'send' a combined Protective Earth/Neutral (PEN) conductor to 'partner' the live. - The neutral for the system being derived from that.
Now... Let me get back to your original questions...
If you have a portable generator and you plug for instance a fridge or any appliance directly into it, how is the neutral/earthing provided??
Well... Earth is the Earth itself; literally Terra-firma. You could connect to the earth of an existing system or connect the frame of the generator to a buried rod. If you don't, the generator - and potentially the appliance - is not earthed.
- And it's because the manufacturers cannot be sure that their generators
will be earthed that they leave the as output 'floating' - effectively L1 L2 (like wot the Yanks use) or the 'push-me-pull-you' ends of the single phase.
If you just connected (for example) L2 (as 'nominal' neutral) to the frame/earth pole of the generator
and fail to tie it to an effective earth you can create a situation where the frame is sitting at a high enough voltage relative to earth to present a shock hazard! - Not only the frame of the generator but any appliance with an 'earth' connector!
This is a significant hazard in the film, TV and entertainment industries where generators for high-powered lighting and signal equipment are common. - One thing I'd strongly advise against is making up ANYTHING that links Neutral/Earth at the generator output! - This could only ever be safe if the operators fully understood the issues and you could be guaranteed that the generator would only ever be used connected to a proper earth.
