Confusion over PV connection to grid

[akaPABLO01]

Wrong again.......

So, why do SMA manufacture this system:

http://www.windandsun.co.uk/product...ms/SMA-Integrated-Storage-System#.WYMcOclwbqA

Another thing is that I have received no reply back from elsta or landis and gyr metering

 

[jcb360]

I discussed many scenarios with him
1. If a large site has machinery that stores electricity through capacitors and the site is active, solar is providing 50% and grid 50%. Then all machines are switched off for lunch which store electricity which then dissipates back into the site network how is this not registered as export with solar?

2. How does solar with battery storage know how it is storing solar, it can't just operate 1 singular way receiving storage from solar. Storage banks are set up to draw electricity off peak and dissipate peak time meaning 2 way.

3. The network was built as a 1 way transfer, network transformer to site. This meaning electricity does not flow to your socket and reverse back on grid. It is transferred at 240 V. Export is transferred at higher voltage to ensure export, 2 way flow.

4. You solar produces at a dc voltage around 630v. This is then transferred into AC at a higher voltage than network in order to EXPORT.

This concludes that all generation is produced at higher voltage and exported and it is the meter which separates network lower voltage from inverter higher voltage. The meter either registers export with import and either puts a kW on or freezes is demand is lower than inverter production.

This must be so, generation cannot mix with network until it hits the grid and all energy must be drawn from the grid.

More half baked pseudo electrical engineering.

Why don't you read the answers the OP received to the same question over on the Navitron forum?

 

[upnortheast]

100 posts and still clear as mud.- think I will stick to milking cows,

 

[jcb360]

Here's a study which proves that PV generation is used on site, in preference to being exported, if there is on site demand for the power:

http://www.energence.co.uk/energy-s...onitoring-energy-management-device-emd-trial/

 

[Exfarmer]

I discussed many scenarios with him
1. If a large site has machinery that stores electricity through capacitors and the site is active, solar is providing 50% and grid 50%. Then all machines are switched off for lunch which store electricity which then dissipates back into the site network how is this not registered as export with solar?

2. How does solar with battery storage know how it is storing solar, it can't just operate 1 singular way receiving storage from solar. Storage banks are set up to draw electricity off peak and dissipate peak time meaning 2 way.

3. The network was built as a 1 way transfer, network transformer to site. This meaning electricity does not flow to your socket and reverse back on grid. It is transferred at 240 V. Export is transferred at higher voltage to ensure export, 2 way flow.

4. You solar produces at a dc voltage around 630v. This is then transferred into AC at a higher voltage than network in order to EXPORT.

This concludes that all generation is produced at higher voltage and exported and it is the meter which separates network lower voltage from inverter higher voltage. The meter either registers export with import and either puts a kW on or freezes is demand is lower than inverter production.

This must be so, generation cannot mix with network until it hits the grid and all energy must be drawn from the grid.

This is complete and utter bulls**t

inverters will convert the DC voltage, which will vary depending on the numbers of panels and the sunshine .
They convert the energy to a sufficient voltage to ensure it is dissipated. if the power is all used on site then it will only need to convert it to to the incoming voltage which should be anywhere between 216 and 253 volts legally. outside these parameters the trips should go.
The inverter should be set to trip if 253 volts is exceeded.

The voltage varies in the network depending on the size of the feed , the length and size of cable from the mains generator, i.e. at the other end of the National grid network.
Your local DNO has to guarantee that their cabling. can bring the Grid voltage to your property within the legal parameters at all times.
When you install PV or other generation the DNO has to approve the install to guarantee their cabling can remove any excess power with in the parameters. If not they will require you to pay for their upgrade to the local network.
electricity will flow to wherever there is an earth a construed earth as in the neutral or to match a Potential difference across phases, indirectly back to the earth.
This flow will cause a reduction in the voltage on the incoming line , in the case of a long extension lead this is easily measured and the effect will sometimes cause motors to burn out if the lead is too long.
Exactly the same happens in the grid.

When you are using no power from your generation the inverter will have to up the voltage very marginally above that of the grid to force the power back into the network, via your local transformer.
there is absolutely no way the power can go both ways at the same time in the same cable, it would be defying the laws of physics. Anyone who tells you this deserves to be sacked.
However , it is perfectly possible for energy to be imported on one phase but being exported on one or both of the other two.

 

[akaPABLO01]

More half baked pseudo electrical engineering.

Why don't you read the answers the OP received to the same question over on the Navitron forum?

I can't see a navitron link can you pm it please

 

[jcb360]

I can't see a navitron link can you pm it please

https://www.navitron.org.uk/forum/index.php/topic,28676.0.html

 

[akaPABLO01]

This is complete and utter bullpoo

inverters will convert the DC voltage, which will vary depending on the numbers of panels and the sunshine .
They convert the energy to a sufficient voltage to ensure it is dissipated. if the power is all used on site then it will only need to convert it to to the incoming voltage which should be anywhere between 216 and 253 volts legally. outside these parameters the trips should go.
The inverter should be set to trip if 253 volts is exceeded.

The voltage varies in the network depending on the size of the feed , the length and size of cable from the mains generator, i.e. at the other end of the National grid network.
Your local DNO has to guarantee that their cabling. can bring the Grid voltage to your property within the legal parameters at all times.
When you install PV or other generation the DNO has to approve the install to guarantee their cabling can remove any excess power with in the parameters. If not they will require you to pay for their upgrade to the local network.
electricity will flow to wherever there is an earth a construed earth as in the neutral or to match a Potential difference across phases, indirectly back to the earth.
This flow will cause a reduction in the voltage on the incoming line , in the case of a long extension lead this is easily measured and the effect will sometimes cause motors to burn out if the lead is too long.
Exactly the same happens in the grid.

When you are using no power from your generation the inverter will have to up the voltage very marginally above that of the grid to force the power back into the network, via your local transformer.
there is absolutely no way the power can go both ways at the same time in the same cable, it would be defying the laws of physics. Anyone who tells you this deserves to be sacked.
However , it is perfectly possible for energy to be imported on one phase but being exported on one or both of the other two.

Unfortunately you've misunderstood my post. I stated that dc voltage is produced at a higher rate, my installs consist of usually 20 panels per string some 600 plus DC< voltage. Converter to ac parameters but dispersed at a fractionally higher voltage then grid Within the legal parameters. I'm not suggesting the 600v dc is transferred at this level in AC

 

[Exfarmer]

Unfortunately you've misunderstood my post. I stated that dc voltage is produced at a higher rate, my installs consist of usually 20 panels per string some 600 plus DC< voltage. Converter to ac parameters but dispersed at a fractionally higher voltage then grid Within the legal parameters. I'm not suggesting the 600v dc is transferred at this level in AC

when in a great big hole stop digging!
you stated

This concludes that all generation is produced at higher voltage and exported and it is the meter which separates network lower voltage from inverter higher voltage. The meter either registers export with import and either puts a kW on or freezes is demand is lower than inverter production.

This must be so, generation cannot mix with network until it hits the grid and all energy must be drawn from the grid.

The meter only registers direction of flow and the amount of the flow. It separates nothing.
if production is 30 Kw, usage is 40Kw flow will be import at the rate of 10KW / hour, i.e. 10 units.

If production is 40 Kw and usage is 30 Kw flow will be export of 10 units per hour. The production , usage and flow will be varying all the time of course.
The actual voltage difference at the meter will be negligible in a properly constructed system except possibly when a large motor is started

 

[akaPABLO01]

https://www.navitron.org.uk/forum/index.php/topic,28676.0.html

Hmm. No REAL answers there but only this

Quote
If my PV is producing more than I am using, can I be self sufficient?
- if you mean 'no instantaneous import whatsoever' then yes, however that is fairly meaningless IMHO

I assume you have a 3 phase system. Being pedantic it is possible to be exporting and importing at the same time with 3 phase.

e.g. assume you are generating 6kW on each phase (18kW in total) and someone is consuming 10kW on one phase. You will be importing 4kW on one phase and exporting 6kW on each of two phases.

The meter should however be able to handle this and show no import. If you had a three phase export meter it would show 8kW export.

Be aware that a small number of three phase import meters incorrectly added export to the import

This from 3 pages is the only remotest plausible theory I can extract from that thread.

However, I've now been told by 2 SMA engineers, 1 German and 1 English that all energy generated is placed onto the grid 100%. (1 based in U.K. And other in Germany)

this just doesn't make sense with SMA. Why do these people (&myself) believe this.

 

[akaPABLO01]

when in a great big hole stop digging!
you stated


The meter only registers direction of flow and the amount of the flow. It separates nothing.
if production is 30 Kw, usage is 40Kw flow will be import at the rate of 10KW / hour, i.e. 10 units.

If production is 40 Kw and usage is 30 Kw flow will be export of 10 units per hour. The production , usage and flow will be varying all the time of course.
The actual voltage difference at the meter will be negligible in a properly constructed system except possibly when a large motor is started

So you've concluded I think the inverter transfers AC at 600+ volts?

Inverters shut down at about 266v ac

 

[akaPABLO01]

when in a great big hole stop digging!
you stated


The meter only registers direction of flow and the amount of the flow. It separates nothing.
if production is 30 Kw, usage is 40Kw flow will be import at the rate of 10KW / hour, i.e. 10 units.

If production is 40 Kw and usage is 30 Kw flow will be export of 10 units per hour. The production , usage and flow will be varying all the time of course.
The actual voltage difference at the meter will be negligible in a properly constructed system except possibly when a large motor is started

Why doesn't grid export? If a site has a supply, 50kW and nothing is being used, and load is at the socket and 10kW of solar is produced why does this 10kW enter the grid? Surely it should mix with supply with that circuit, what separates it from supply at socket and exports 10kW?

 

[akaPABLO01]

British Gas just called and could not answer. It's been escalated

 

[akaPABLO01]

@jcb360 & @Exfarmer

As above

If your site has a 50kW incoming supply at socket and solar is switched off you have 50kW available to draw.

If you have 10kW solar and switch this on and nothing is drawing down you export 10kW.

You claim if you have a usage of 10kW you use the solar first, this must mean then that it mixes on your site with the incoming supply.

If you have no use of this 10kW solar it exports. How does the meter identify that 10kW is solar export if it's mixed with network supply on site?

The identifier must be higher solar voltage to grid voltage and all generation must be exported with the meter identifying draw versus solar export.

If solar was used first on site then it would mix with network on site therefore making it redundant for export monitoring.

 

[e3120]

 

[jcb360]

@jcb360 & @Exfarmer

As above

If your site has a 50kW incoming supply at socket and solar is switched off you have 50kW available to draw.

If you have 10kW solar and switch this on and nothing is drawing down you export 10kW.

You claim if you have a usage of 10kW you use the solar first, this must mean then that it mixes on your site with the incoming supply.

If you have no use of this 10kW solar it exports. How does the meter identify that 10kW is solar export if it's mixed with network supply on site?

The identifier must be higher solar voltage to grid voltage and all generation must be exported with the meter identifying draw versus solar export.

If solar was used first on site then it would mix with network on site therefore making it redundant for export monitoring.

In simplified terms, the electricity meter measures current flow - Amps. It can also determine direction of current flow.

Why don't you try the experiment with the clamp meter and load of known size I suggested a few pages back?

If you are a solar installer, surely you or your electrician have a clamp meter?

The theory is valid whether the micro generation connected is via inverter or asynchronous generator.

 

[akaPABLO01]

In simplified terms, the electricity meter measures current flow - Amps. It can also determine direction of current flow.

Why don't you try the experiment with the clamp meter and load of known size I suggested a few pages back?

If you are a solar installer, surely you or your electrician have a clamp meter?

The theory is valid whether the micro generation connected is via inverter or asynchronous generator.

But if solar has mixed with site "flow" how is solar given preferential export?

I know about amps, I simplyfied the network flow to be 50kW whether that be 100amp/ phase or not to make my point about "flow"

If demand is 10kW and no solar then 10kW is drawn to compensate current already in the site circuit. If solar supplies this then no current is drawn.

How is solar "flow" different to network flow that registers export after mixing with site circuit flow?

You are still not giving me a solid answer to my question.

 

[Exfarmer]

I am sorry but am I missing something, has Pablo lost his own plot?

 

[akaPABLO01]

I am sorry but am I missing something, has Pablo lost his own plot?

Nope, I'm asking a valid question which probably needs someone with a higher understanding of physics coupled with electrical depth.

The answers I'm receiving do not have depth or full breakdown here or navatron. Albeit, the one reply I quoted from nab holds some weight.

Electricity network was designed for a 1 direction flow. Solar mixes with site electricity on demand and is used on site. When it is not in demand it "flows" why does it flow grid bound. It must be transmitted at higher voltage therefore all must flow grid bound and the meter compensates either adding units or declaring a portional export or full export.

There is no weight in any answers here and frankly I think it's all guess work as 50% believe it all goes grid bound and the other site usage. Everyone has an opinion but nobody has the scientific explanation.

I think I'll email some more people over the weekend when I get downtime

 

[Exfarmer]

Just think of voltage, like pressure in a water pipe, the water will always flow to the point of lowest pressure. The same is true of electricity, for current to flow the voltage must be higher than the the background voltage, its called potential difference. Turning on a switch lowers the voltage and current flows into the light/ motor whatever to correct the difference
Current comes from the mains but you can push it back up by raising your voltage, this will only be a very small amount as the grid can absorb an awful lot and you will be limited by the wires to your source. The lighter the wiring the higher you will have to push the voltage to force the current back.
I think you are confused by the alternating nature of DC where the power is indeed pulsating, but the current is actually only ever flowing in one direction