It's about not having too much unbalance between the load on each phase, not really the size of the load itself.
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Universal Mobile Connector (UMC) in Australia
- Thread starter Power Hungry
- Start date
OzTzlaBloke
Member
How does that matter in single phase? Everywhere else in States of Aus where physics remains the same, thinks it doesnt. Im going 7KW single phase in NSW no problem.
It matters because it contributes to an overall phase unbalance at the low voltage transformer, which wastes energy and reduces overall network capacity due to higher losses in the transformer and in the neutral conductor.
Yeah. If you and your neighbours all agreed to use the same amount of single-phase power at the same time, and were connected to different phases of the grid, it'd be ok. I assume that the smaller and more spread out population in Queensland makes it harder to balance the loads? For me, I live right near a hospital and other major consumers of energy. Anything I do in either power consumption or production will be a rounding error in the local network, but I can appreciate the rules have to apply to everyone.
One of my goals is to use power in the middle of the day, smoothing the top off my solar export curve for the sake of network stability. I'd just love that to be more automated than it currently is, especially for consumers who don't want to have to think about it. I assume the grid will get smarter over time, with community batteries vehicle-to-grid, etc.
OzTzlaBloke
Member
Brilliant thankyou
Wonder if QLDers could persaude permit type policy to do it and pay a fee for these added losses in the overall infrastructure? The ban it approach in peak vs offpeak seems kinda harsh and authoritarian
I’m not aware of any easy way to find out what firmware version the UMC is on. The UMC firmware is updated by the car if needed after a charging session is finished.
My UMC was supplied with my car in 2019 and came with 8/10A and 12/15A tails. The 10/10A and 15/15A tails I bought last month worked the first time I plugged them in, which implies the UMC firmware was updated on some previous charge, even with the old tails plugged in.
UMCs supplied since 2021 come with 10/10A and 15/15A tails.
It has been a mixed bag. A bunch of people received 8A/12A tails in their UMC kits earlier this year (mine had a CCS Combo Adapter as well). They may have been old stock, but they were ordered and delivered this year.
Same here. My grid voltage often hits 248V around 1130am -1300pm. Admittedly it's because the street step down transformer is in front of my house on the light pole so not much voltage drop to my house compared to the last house in the street and I'm pushing a huge amount of solar export.
If the properties ever redevelop and install solar panels, the grid voltage at the transformer will go over 250V limit at midday and trip my inverter export function.. Ausgrid says they can turn down the transformer taps but the problem then becomes an issue for the last house at peak grid demand causing lower voltages.
The overvoltage will be more a problem for those down the end of the line. The transformer will keep your end from deviating too much in either direction.
No, the overvoltage is a problem for those close to the transformer as the voltage is always highest at the transformer and less of a problem for those at end of the line - due to voltage drop mainly from electricity demand - especially in the evenings where there is no solar. Voltage drop due to distance not a big issue apparently.
Some transformers are "smart" and can dynamically adjust output voltage. Unfortunately these are modern units and not a lot of these around. Most older residential street transformers on the poles are static transformers which require manual adjustment of output voltage.
When the street was built and the local grid designed, residential solar power and grid export was not even on the horizon and the street voltage was adjusted to allow all the houses within the transformer supply area to be within a specified voltage range. Residential solar export then impinges on the headroom between street voltage and the hard limit of 250V. The more solar that gets exported the less the voltage headroom is especially around 12 noon.
Undervoltage on the other hand is not good either, because while it is great for those close to the transformer and allows headroom for people like me to export, the voltage drop to the end of the line may make it unsafe for them.
The voltage is only higher at the transformer side when the transformer is supplying power. The voltage drops in the direction that power is flowing. When solar exports are very high and many houses on the circuit are supplying power, the voltage ends up raised at the end of the line where the exporting houses are.
The transformer has very low impedance and strongly drives the voltage on the low-voltage side to the feeder voltage divided by the turn ratio.
The same thing happens within your house. The voltage will be lower at your EV charger charging at 32A than at your point of attachment, but it'll be higher at your PV inverter supplying 16A than at the point of attachment.
Correct, but the voltage at the transformer output is set irrespective of the output (unless it's zero output). In order to export to the street, the inverter export voltage must be higher than the street voltage. This causes the street voltage to rise depending on the ratio between what the transformer is supplying and what the inverter is supplying.
Yes the voltage will reduce in the direction of flow. The house furthest from the transformer will see the lowest voltage. But what is the highest voltage and where it is, is my problem - because closest to the transformer will always be the highest.
If the houses at the end of the line install solar and export, the voltage will rise there, but because the street voltage is lower there, they have more voltage headroom to export. And depending on the street export vs demand, it could push the voltage at the transformer output higher, reducing my voltage headroom
My house which is closest to the transformer always sees the highest voltage in the street. Even in the evenings the voltage is invariably 245-246V. At 12pm peak solar output the inverter voltage hits 248-249V.
At some point if street solar production is more than consumption, power will flow in reverse back through the transformer. However, currently mine is the only house with solar- that I can see. This means that if houses start installing solar further down the line, the street voltage could rise - reducing the voltage drop. And potentially my inverter could see 250V and stop exporting. I'm basically 1-2V under the inverter cutoff on many peak solar days.
Last edited:
raynewman
Active Member
The rise is dependent on the current exported and the impedance back to the transformer.
Closest to the transformer will be the least variable.
The voltage is lower there because of the power drawn through the higher impedance back to the transformer. If they all switch from importing to exporting, that impedance works the other way and they'll see a large voltage rise. The best situation for those houses is if some of them are exporting and some importing, bringing the voltage closer to nominal.
Almost all of that 3V rise would be between your inverter and your point of attachment.
Is your inverter set to drop out over 250V? The Australian standard says 10 minutes sustained above 255V, or any time over 260V. Of course your DNSP might have set tighter requirements, but it's worth asking your installer if the settings can be loosened.
If I recall the 2014-2019 or so Ss and Xs were base 11kW, with a $4k? Dual charger (22kW) option.
Later Ss and Xs were down the middle at 16.5kW
I studied electrical engineering and worked for a short while at a distributor but I no longer work in the field (and have never been an electrician, too much crawling around in hot roofspaces for me!). I do keep up with what's going on around the electricity system in Australia, because it's an exciting time with a lot of change that's pretty relevant to all of us.
My 2018 S came with the 22kw charger. It was not an optional extra. I think it all changed when the new nose shape was introduced.
That's what the installer said for the 3p SMA inverter. He has "cranked" it up the the max allowed. He could be wrong about the actual limit condition.
The Ausgrid guy came around and would not lower the transformer voltage because it was below 250V (246V) when he measured it. One of the reasons I was told for the higher voltage is because I am semirural so the voltage needs to allow for voltage drop to the furthest house.
Here is a screenshot from today at 12:30pm
I'm hoping no one installs significant solar and then export. There is no limit to export in my area and I exported circa 20MW in 2022. So I'm hoping (selfishly) that the neighbours don't put up large exporting arrays.
It is what the inverter sees that is the issue - for me at least.
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