Voltage question.

[Kelvin]

1 hour ago, -rick- said:

 

I assume you mean readable output. Just had a thought, do either of them have an ESPNow firmware you could flash onto them? If they don't monitor current/power usage at all, then ignore.

Yes Home Assistant refers to readable outputs as sensors. 
 

I rummaged around in my box of stuff and came across a Shelly energy meter  so that should allow me to monitor it. 

[Dillsue]

5 hours ago, Beelbeebub said:

Thanks all. 

 

I'm just a little worried as my inverter shuts down if the voltage goes too high (253.6 for more than a certain time) - nothing dramatic, it just dumps me back to grid power - which is annoying as I then start consuming grid power even though my panels and battery are able to support me. 

 

Currently my export is set to 2kw limit pending the paperwork coming through for higher (waiting on installer). But the other day it threw some warnings and shut down briefly. 

 

It's nit the end of the world if I can't export much, though I do have a bunch to spare, but having the inverter shut down from time to time because the operators are running to close to the upper limit would be annoying. 

 Shutting down at 253.6v seems overly close to the limit....my 2 solaredge inverters dont trip til they hit 262v. If that figure of 253.6 is adjustable, I'd raise it slightly whilst you sort things out with your DNO

 

G98 allows you to export up to 3.68kw without seeking permission and your DNO should ensure that when exporting at that rate that your voltage stays below the 253v limit. If you're going over 253v with 2kw of export, things will only get worse with more export. As a minimum your DNO should ensure you can push 3.68kw into the grid and stay below 253v. Is your installer putting in a G99??

[Kelvin]

Solved this in a different way. The Zappi tracks the voltage as a diagnostic in Home Assistant. 

[Kelvin]

The AC voltage at the inverter is slightly higher than what the Zappi is showing. The Zappi is reading this at the meter. The drops (sag) is me initiating charging the storage battery as I was testing being able to control it and automating it from Home Assistant. I’ll check it again tomorrow as it will be a slightly better day for solar generation. 
 

Edited Sunday at 21:50 by Kelvin

[-rick-]

Those are some quite chunky drops. Guess thats what you get for being in the sticks at the end of a long wire?

[Kelvin]

The mains cable is only 23m from the overhead line to the meter cabinet and this is being measured at the meter tails. I’ll set up Shelly and have it measure the V at the CU to compare. I have a 12kW inverter and I had it set to charge at 8kW although I’ve settled on 5kW for normal use. 

[-rick-]

1 minute ago, Kelvin said:

The mains cable is only 23m from the overhead line to the meter cabinet and this is being measured at the meter tails. I’ll set up Shelly and have it measure the V at the CU to compare. I have a 12kW inverter and I had it set to charge at 8kW although I’ve settled on 5kW for normal use. 

 

Voltage isn't measured by the CT at your meter. It's measured at the device, so where your Zappi is. CT measures current. Is there a transformer on the pole or is the overhead line 240V? If the latter, then when I said long wire I meant to the nearest transformer.

[Kelvin]

Yes of course. Apologies,  I wasn’t very clear. What I meant is the Zappi is installed at the meter on a short cable run rather than elsewhere in the house. The transformer is on the next pole adjacent to the pole I’m attached to. There seems to be a nominal 3V difference between what the inverter shows and what the Zappi shows. Measuring using my multi-meter and it matches the inverter. 

Edited 18 hours ago by Kelvin

[jack]

18 hours ago, SteamyTea said:

What do multimeters, or other voltage sensing devices actually measure?

Is it peak voltage (V_p), the full voltage (V_p-_p) or the average voltage (V_avg).

When it comes to AC and power delivery, it is usually to use RMS values (root means squared).

The same is done with current.

When the two are multiplied together, the product is the DC power equivalent.

 

Mains voltage is RMS.

 

Multimeters nominally display RMS, but I think cheaper ones do something like measuring the average peak and estimating RMS by dividing by the relevant factor (sqrt 2, roughly 1.4). This assumes a perfect sine wave. The further from a perfect sine wave the input signal is, the more incorrect the value will be.

 

Better ones will display "true" RMS, which involves performing the actual RMS calculations based on sampled voltage values. There's a lot more to calculate, so you need more memory and processing power, hence true RMS meters are more expensive. 

[-rick-]

45 minutes ago, jack said:

There's a lot more to calculate, so you need more memory and processing power, hence true RMS meters are more expensive. 

 

Certainly true in the past but today when microchips are so capable it's not really an excuse any more. If a multimeter doesn't have truerms it's almost certainly deliberate market segmentation by a company trying to milk as much money from you as possible, find another company.

[Beelbeebub]

So this morning my panels were charging my batteries at about 7kw, with around 500w going to my house.

 

The grid voltage was low 240's, maybe 242, 245 etc. 

 

Then around 12.40, my battery hit 100% and the system switched to export mode. 

 

The DNO limited me to 3.7kw (I can see why) but even so.my voltage jumped well over 250, peaking at 255!

 

It seems to be stabilising around 250ish now, but my connection seems to be a bit crap. 

 

I alps noticed they limited me to a 75a supply but I'm pretty sure we have a 100a fuse! 

 

[Dillsue]

7 minutes ago, Beelbeebub said:

The DNO limited me to 3.7kw (I can see why) but even so.my voltage jumped well over 250, peaking at 255!

 

 

That's the G98 limit that everyone has a concession to export. If your voltage is going over 253v and it's concerning you then let your DNO know and they'll sort it out for you.....they're obliged to if your sticking to 3.68kw of export.

[Beelbeebub]

39 minutes ago, Dillsue said:

That's the G98 limit that everyone has a concession to export. If your voltage is going over 253v and it's concerning you then let your DNO know and they'll sort it out for you.....they're obliged to if your sticking to 3.68kw of export.

Yeah, they basically stuck me the bare minimum, and I suspect (given the voltage rise) they would have set it to zero if they were allowed. 

 

I"ll monitor the voltage and see if they can/will make the required adjustments. 

 

I do wonder, I'm in a long thin village and not too far from the transformer. But some other people, presumably on the same line will be a lot further. If the cables are a bit skinny it's possible they have to set the transformer voltage at the high end so the people furthest away aren't too low.  If that's the case there may not be much room for adjustment. 

 

Oh well. It's not the end of the world, it would be nice to be able to get more export money but ultimately the better option would be to find another use for the spare capacity <starts scrolling through autotrader> 

[DamonHD]

If we are going to electrify everything to achieve Net Zero then the DNO is going to have to deal with much bigger power demands in both directions eg from PV generation and EV charging.  Upgrades will need to happen.  I think that the DNOs accept so.  It is not your problem to make that happen.

[Dillsue]

7 minutes ago, DamonHD said:

If we are going to electrify everything to achieve Net Zero then the DNO is going to have to deal with much bigger power demands in both directions eg from PV generation and EV charging.  Upgrades will need to happen.  I think that the DNOs accept so.  It is not your problem to make that happen.

Exactly.

 

When we added more PV our DNO stumped up for a new transformer, 3 new poles, 100metres cable, pole anchors, earth loops etc. That brought the supply up to modern standards. The neighbours now run through the summer days on our PV. It's also meant that when we recently applied to hook up an EV charger and heat pump the supply was up to spec and got approved in a couple of days.

 

I would imagine that much if not all of the cost of upgrades to hit net zero are coming from the bill payer and central government so minimal cost to the DNOs??

Edited 13 hours ago by Dillsue

[SteamyTea]

1 hour ago, DamonHD said:

Upgrades will need to happen.  I think that the DNOs accept so.

Bit more than accepting, they have a plan.

https://www.nationalgrid.com/media-centre/press-releases/riio-t3-business-plan-published-framework-deliver-most-significant-step-forward-uks-transmission

 

At £35bn over the next 5 years, it is not too expensive in infrastructure terms. 

[Beelbeebub]

Dunno, there's the corroding and falling apart lead sheathed, paper insulatied main feed to a block of 4 flats I look after that clearly runs hot, the pitch potting in the head is leaking out that we repeatedly point out to the dno (basically every time an electrician comes in and goes "holy shit". 

 

And every time somelne comes out, agrees it's crap and needs replacing and then bugger all happens.

 

I've still got several tenants on the old radio switch meters. Repeated visits by meter swap teams have failed to actually swap the meters.... 😞