Dave, seen this? Grid overvoltage story in the Guardian - Page 1
Forum section: electronics / general

author: Mr Purple
author_rank: Newbie
timestamp: October 19, 2024, 05:26:44 am
content: https://www.theguardian.com/australia-news/2024/oct/19/could-australias-outdated-voltage-standards-be-taking-years-off-the-life-of-your-toaster

author: tszaboo
author_rank: Super Contributor
timestamp: October 19, 2024, 08:41:04 am
content: I wonder what appliance uses less energy with less voltage? SMPS will have higher efficiency. Space and water heaters will use the same, because they need to be on for longer to heat up. Motors will rotate at the same speed, and their consumption is mostly dependent on the load.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: October 19, 2024, 09:14:37 am
content: As mentioned above, a large proportion of loads will draw about the same total energy over a range of voltage, but at lower voltages, transmission losses will be higher, so I wonder if that would offset any gains from those appliances that draw less at lower voltages.

author: tooki
author_rank: Super Contributor
timestamp: October 19, 2024, 11:09:07 am
content: Quote from: tszaboo on October 19, 2024, 08:41:04 amIncandescent light bulbs I guess?OK, in fairness, old gadgets with linear regulated power supplies would burn off more waste energy as heat with higher input voltages.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: October 19, 2024, 03:05:10 pm
content: Quote from: tooki on October 19, 2024, 11:09:07 amLED bulbs with capacitive droppers, vacuum cleaners, some motors in washing machines, ceiling fans, aircons & heaters that are run full blast so the thermostat never kicks in.

author: coppice
author_rank: Super Contributor
timestamp: October 19, 2024, 03:08:19 pm
content: Quote from: tooki on October 19, 2024, 11:09:07 amI wonder what percentage of total electronic load on the grid is linear supplies in 2024?

author: ejeffrey
author_rank: Super Contributor
timestamp: October 19, 2024, 04:34:10 pm
content: Quote from: mikeselectricstuff on October 19, 2024, 09:14:37 amPresumably this would be accomplished by changing taps on neighborhood or individual customer transformers whenever they do service, not lowering the voltages on long distance transmission lines. So the impact on transmission losses would be quite small either way. Constant power devices would see their net transmission losses go slightly up, while resistive loads with thermostats would have losses go down slightly due to spreading the load out over more time.

author: wraper
author_rank: Unknown
timestamp: October 19, 2024, 04:38:08 pm
content: Quote from: tooki on October 19, 2024, 11:09:07 amAny resistive stuff, such as space heater, kettle, toaster, clothes iron, hair drier.

author: coppice
author_rank: Super Contributor
timestamp: October 19, 2024, 04:41:22 pm
content: Quote from: wraper on October 19, 2024, 04:38:08 pmmost of that stuff just finishes the job faster, and takes no additional energy.

author: wraper
author_rank: Unknown
timestamp: October 19, 2024, 04:51:20 pm
content: ^Out of things I mentioned it's applicable to clothes irons and electric kettles. Some space heaters depending on room temperature.

author: tooki
author_rank: Super Contributor
timestamp: October 19, 2024, 05:48:36 pm
content: Quote from: wraper on October 19, 2024, 04:38:08 pmThose will use less power, but the same energy because they need to run longer.

author: tszaboo
author_rank: Super Contributor
timestamp: October 19, 2024, 07:18:34 pm
content: Quote from: coppice on October 19, 2024, 03:08:19 pmI wonder how many MBAs working at the power company, giving interviews know the difference between power and energy.Scary these are the same people that make decisions.And even in the article, solar power baaad. Big bad. Except the voltage is somehow higher during the night.

author: coppice
author_rank: Super Contributor
timestamp: October 19, 2024, 07:27:43 pm
content: Quote from: tszaboo on October 19, 2024, 07:18:34 pmWhen the EU set limits on power consumption for some appliances, like vacuum cleaners, it made some sense. Manufacturers had been competing with higher and higher power ratings, but using horribly inefficient motors. Sounds sensible. As soon as that was enacted they started talking about capping the power of things like kettles. Maybe their first effort just hit a sane target by luck.

author: TimFox
author_rank: Super Contributor
timestamp: October 19, 2024, 09:26:03 pm
content: In physics, we make a careful distinction between power, energy, strength, force, momentum, etc.In normal English, these words are often considered synonymous.A common problem when science encounters the general population.

author: Whales
author_rank: Super Contributor
timestamp: October 20, 2024, 06:39:57 am
content: Quote from: wraper on October 19, 2024, 04:51:20 pmClothes irons and electric kettles both have control loops, they heat until a threshold temp is hit. Lowering their on-state power draw won't appreciable change their total energy draw (and in the case of a kettle may increase it, because more time is spend wasting heat to the environment).

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: October 20, 2024, 08:02:20 am
content: Quote from: ejeffrey on October 19, 2024, 04:34:10 pmI'm talking about losses in the cabling from the transformer to the house - relatively short distance, but a lot of it - no idea of the avarage resistances involved.

author: coppice
author_rank: Super Contributor
timestamp: October 20, 2024, 05:04:04 pm
content: Quote from: Whales on October 20, 2024, 06:39:57 amTo be more precise, only a small number of kettles - those which allow you to set a target temperature, heat the water, and hold it at that temperature - have control loops. Most kettles just cut out when the water boils. Either way, they only use the required energy. If they used more there would be a lot of steam peeling the decorations off the walls.

author: tszaboo
author_rank: Super Contributor
timestamp: October 20, 2024, 06:12:01 pm
content: Quote from: mikeselectricstuff on October 20, 2024, 08:02:20 amTypical grid impedance is 100-200mOhm. In your house, there are ~16 AWG wires for ~15m, which might double this ballpark.So for 230V and 2300W ultra turbo non EU conform kettle, 10A, the losses are 20-40W. Let's say 1.5%.If you reduce the voltage (no idea why but let's just entertain it) to 95% of it's nominal, then the current goes down to 95% and the losses go down 1-(0.95*0.95) -> 10%. Also known as 0.15% or the technical term I believe is f* all.

author: wraper
author_rank: Unknown
timestamp: October 21, 2024, 05:49:27 am
content: Quote from: tooki on October 19, 2024, 05:48:36 pmHalf of those are not even temperature controlled.

author: Jeroen3
author_rank: Super Contributor
timestamp: October 21, 2024, 06:13:53 am
content: What a weird article. They blame the voltage, but actually it's the at capacity last mile LV network. Most older network I'm, sure in AU also were laid out with a lower "typical household" load then today.QuoteNo, that's not how it works. Voltage is not a reflection ofgridcapacity. The bottlenecks can be upstream in MV or HV networks, then your LV voltage doesn't create capacity. The grid operator may even intentionally raise the LV network to curtail PV systems. As they do here in holland in some oudated regions.

author: wraper
author_rank: Unknown
timestamp: October 21, 2024, 07:48:09 am
content: Quote from: Jeroen3 on October 21, 2024, 06:13:53 amThe issue is that although AU has 230V nominal instead of old 240V, all they did is put the new nominal number 230 V with high high side tolerance (+10% to -6%). So nothing changed in practice, but you're supposed to safely use 230V appliances.

author: tooki
author_rank: Super Contributor
timestamp: October 21, 2024, 08:17:37 am
content: Quote from: wraper on October 21, 2024, 05:49:27 amYes, they are. The only one of those thatisn’ttemperature controlled is the toaster — but the user will have to toast for longer to get the color they want. Similarly, if someone is using an old-fashioned hair dryer without temperature control, they’ll need to run it for longer.

author: jonpaul
author_rank: Super Contributor
timestamp: October 21, 2024, 08:23:21 am
content: IEC, NEC, UL and other utility spcs exist for the allowed limits on mains voltage.Normally a PSU/SMPS/consumer device has a band of acceptable voltage areound a nominal.https://www.power-sonic.com/blog/single-phase-and-three-phase-voltage-by-country/In US the nominal was changed over the years 100>>110>117.Tolerance band can be 8,10,12%.Modern PSU topology includes a PFC that accepts any mains eg 70..260V and outputs a 360V DC bus with a boost PFC.Jon

author: tooki
author_rank: Super Contributor
timestamp: October 21, 2024, 08:49:54 am
content: Quote from: jonpaul on October 21, 2024, 08:23:21 amNominal was never 117V. That was a labeling compromise between 115V and 120V, the latter of which has been the nominal voltage for nearly a century.

author: Berni
author_rank: Super Contributor
timestamp: October 21, 2024, 09:59:43 am
content: Yep this is pointless.The biggest difference is for resistive heaters, yet most of those run on some form of thermostat.So the only thing remaining is appliances with high power brushed motors like vacuum cleaners, angle grinders etc.. that will be slightly less powerful. This most certainly will not make a 100$ difference in your power bill, even if you love vacuuming your rugs daily.Tho in general power companies try to keep the voltage cranked up because they are compensating for the voltage drop in the lines. They have a specified tolerance window of +x%/-x% so in order to have the best chance of staying in the window they crank it up on the high side so that more voltage drop can occur before it falls out of the bottom of the tolerance window. But the problem is the voltage drop is not always there during low load hours (also solar panels are becoming popular now) so you get the full voltage.Peoples electronic devices die because the engineer that designed it was instructed by the company to make the PSU cheap and not last too long out of the warranty period. If not that then it is a brief overvoltage event (storm or some line fault) that pulls live to 500V for a moment is what kills it, not something that would be any less likely if the AC voltage was smaller.

author: wraper
author_rank: Unknown
timestamp: October 21, 2024, 02:42:18 pm
content: Quote from: tooki on October 21, 2024, 08:17:37 amBarely any hair driers are temperature controlled. Many space heaters are not temperature controlled.

author: Berni
author_rank: Super Contributor
timestamp: October 22, 2024, 05:23:12 am
content: They don't have thermostats but the humans using them will end up using them for longer as they will take longer to get the job done (be it get hair dry or heat up a room).Also most hairdriers have multiple heat settings, so you can use your hairdrier at reduced power whenever you like with a flick of a switch rather than changing the whole line voltage.Tho that being said most cheap vacuum cleaners are horrendously inefficient, mostly thanks to them being traditionally advertised in watts. So what the manufacturer ends up doing is specifying a inefficient loose tolerance impeller (wider tolerance = cheaper to make) that overloads the motor into pulling as much power as possible while also using as thin of a wire as possible on the windings to burn some more watts, then use the immense amount of airflow that a vaccum cleaner produces to blow across the motor and get the heat out so that it doesn't overheat, hence the air blowing out of a vaccum cleaner is really hot, most of that looses. So over here they introduced a law that limits consumer vacuum cleaners to 900W to stop the watts pissing contest (especially here where you can pull 3kW from a normal wall outlet).

author: tooki
author_rank: Super Contributor
timestamp: October 22, 2024, 07:16:04 am
content: Quote from: wraper on October 21, 2024, 02:42:18 pmPerhaps I am biased due to which models are sold in the two countries I spend the most time in (Switzerland and USA), but I have rarely ever seen a space heater without a thermostat, and hair dryers now commonly have thermostatic control. And even the models without true thermostatic control still use some mechanism (either a bimetallic strip or a sensor) to limit the maximum temperature — in addition to the thermal fuse to prevent fires if the airflow is blocked or the fan seizes while unattended.