Stumped!

[Darkwood]

I agree with the inverter bit, the Net metering side however is totally wrong

Well as i say i dont do the installs but i use inverters for other uses, i may be wrong on how the metering side is done and would be more than happy to stand corrected, but as goes electric flow and where it ends up is all down to path of least resistance and if your a long way from the substation it maybe the case it will find its way directly into supplementing your power supply demands, but all you have really done is matched the mains for voltage and frequency as well as syncronising the waveform, once its been coupled up to the mains its destination is purely determined by path of least resistance whether this be sharing the house loads or popping up the mains and helping supplement next doors loads etc etc ... is here nor there but it will be accounted for through the metering system.

 

[Glen Powell]

I am sure I said that in a previous post, you will however find inverters do kick out a slightly higher voltage at peak generation regardless of other factors, the frequency is not in question here as the inverter will not output unless synchronised however there can be deviations between voltages, this is more common on multiple inverter installs are an area where multiple installations are carried out in local area.

The DNO is now plagued with voltage anomilies on the grid and from what I see this is down to a number of installs in same are (this is a different topic all together).

Quality of inverter and how it syncs is just as important, path and resistance already covered to the enth degree me thinks.

 

[Darkwood]

Well with the noise been generated into the mains .. i assume their is a high proportion of modified sinewave inverters as opposed to pure sign wave inverters ( cost been the obvious reason) and i can see these having strict guidelines been applied with a clampdown of their use soon as the DNO are already implementing fines to commercial and industrial firms who are feeding excessive noise into the grid regardless of the cause. Domestic dosn't really get scrutinised as its harder to source the issues but im sure an industry clampdown on cheap inverters is around the corner.

 

[Gavin A]

Well with the noise been generated into the mains .. i assume their is a high proportion of modified sinewave inverters as opposed to pure sign wave inverters

you'd assume wrong, there's no way they'd be allowing modified sine wave inverters to be grid connected (well ok, so essentially all inverters are modified sine wave to a degree, but all would be sold as pure sine wave type if off grid).

Personally I've found it easier to understand this and explain it all via plumbing analogies, but maybe that's because I've got some background in that field as well as renewable energy / electrics, and my scenario here was probably a little complex.

 

[yellowvanman]

Where the inverter and mains meet (say at the mains meter) the voltage is one value, to get to that point the inverter has to generate the ac at a higher voltage to take account of voltage drop from its supply cable and so 'push' current down the cable.

Whatever current is coming down the cable on the line (brown) conductor from the inverter has to return back via the neutral (blue conductor) to complete the circuit, so the round trip of current from the inverter is much shorter than the mains round trip from the nearest transformer, so if the electrons are taking the path of least resistance the current from the inverter is used in the house first and if not enough more is used from the mains!

 

[Darkwood]

Ive also been led to believe the sychronisation of the sine wave is generated at a slight voltage lag to aid the injection into the grid, this and the very small voltage increase together is what give it the pushing force against the incomming grid, is this correct?

 

[yellowvanman]

Ive also been led to believe the sychronisation of the sine wave is generated at a slight voltage lag to aid the injection into the grid, this and the very small voltage increase together is what give it the pushing force against the incomming grid, is this correct?

You're making this more complicated than it is! I don't know whether the inverters do what you are saying, but I'd be surprised if it is, but will stand corrected if anybody knows better.

Looking at it more simply. Lets take Kirchoffs law - sum of all currents at a node = 0.

So lets say the cu, inverter and meter are all connected to a henley block. The inverter is generating some power so it has to go somewhere, so lets say its generating x amps, cu is using y current.

If x > y then the inverter is exporting to the mains at a current (x - y) amps

If x < y then the mains is supplying current to fill the inverter short fall at (y - x) amps

 

[Earthstore]

Well I bet the OP is stumped now.....

 

[snowhead]

Right, explanation no. 49.

To the O.P;

Imagine electricity as a person standing on a staircase.

Now we've got 2 staircases and 2 persons.

The person on the GRID staircase is on step no 4.
So when the sun shines the person on the P.V staircase goes to step no.5 on his own staircase and chucks all his current at the load, your house and beats off the GRID.
Because the GRID now doesn't have to work so hard, he can move up onto step 5.
Not to be outdone, the P.V moves to step 6 and continues to chuck and win.

However, now your nextdoor neighbour turns off his kettle and shower, lightening the load for the GRID allowing him to move to step no 7 chucking all the current he can at your house and winning.
Poor old P.V can't do a thing, no more sun available.
He/she has to sit it out and wait for the Tanning studio down the road to turn on all the sun beds and drag the GRID down a couple of steps.

Summary, whilst ever the P.V can beat the GRID on voltage, it wins.
Of course the movement up and down the stairs is continuous and very quick.

 

[liquidity]

Are these spiral or straight staircases? Any landings?

Sorry; I'll get my coat.