Grid Tied inverters for household use will soon be useless? - Page 1
Forum section: electronics / general

author: Faringdon
author_rank: Super Contributor
timestamp: September 18, 2021, 02:04:39 pm
content: Hi,This is what i mean...https://www.solarquotes.com.au/blog/grid-voltage-rise-solar/GTI's have got serious problems up ahead !!!If people want there own solar generation. Then pretty soon, they are going to have to "island" their household mains from the grid, and just use a standard Non grid tied inverter from the panels to supply their household...This is obvious, do you not agree?

author: NiHaoMike
author_rank: Super Contributor
timestamp: September 18, 2021, 04:34:26 pm
content: Just use an autotransformer to cut the voltage a bit.

author: nctnico
author_rank: Super Contributor
timestamp: September 18, 2021, 04:44:05 pm
content: Quote from: NiHaoMike on September 18, 2021, 04:34:26 pmBut that will increase the grid voltage even more which in the end damages the equipment in your home.

author: Berni
author_rank: Super Contributor
timestamp: September 18, 2021, 05:17:22 pm
content: The power networks need to upgrade to keep up with ever rising energy demands, there is no way around it.We had a too long line to the transformer that was feeling the whole street. It used to be fine, but as demand rose it just did not cut it anymore. We got a solar inverter and it kept complaining and going into safe mode. So i hooked up a DMM to the worst phase and turns out it sometimes dropped down to 180V for a breif moment. They used to compensate for this by choosing a higher transformer tap, but that was too much for the first houses in the line. We sent the chart to the power company, they came over and left there own dataloger for a bit and came to the same conclusion. As a result they decided to run a new line from a transformer, it went mostly trough our land and our relatives so we helped arrange for approval. Ever since the voltage is rock solid and the solar inverter is happy as can be.As electric cars become more popular this is only going to get worse. They take massive amount of power from the grid and they typically get charged at similar times of the day when people come home from work.

author: Monkeh
author_rank: Super Contributor
timestamp: September 18, 2021, 05:19:43 pm
content: Quote from: Berni on September 18, 2021, 05:17:22 pm'ever rising'?But yes, the LV side of the grid is going to have to adapt to significantly different demand peaks and the reality of distributed generation.

author: Berni
author_rank: Super Contributor
timestamp: September 18, 2021, 05:25:51 pm
content: I meant for residential costumers.The largest users of power tends to be industry and those will usually get there own high voltage feed and a dedicated transformer right on the property. They are doing fine and can pump boat loads of solar power into the grid without the voltage going anywhere.The residents on the other hand are fed over long wires from transformer stations dotted about. These have a limited ability in current handling as at some point the wires connecting them produce too much voltage drop. The transformers themselves are also old and got speced according to how much power they thought they will need in the 60sIts not that the grid can't handle all this solar power. It's this last low voltage local distribution step that is struggling.

author: f4eru
author_rank: Super Contributor
timestamp: September 18, 2021, 05:27:51 pm
content: Yep. Old style networks, not designed for strong local generators, but still can handle it to a point.Takes time to phase out, but will happen.

author: NiHaoMike
author_rank: Super Contributor
timestamp: September 18, 2021, 05:49:37 pm
content: Quote from: nctnico on September 18, 2021, 04:44:05 pmNot if you put the sensitive loads on the autotransformer as well. But aren't modern electronics designed for as much as 265V?

author: nctnico
author_rank: Super Contributor
timestamp: September 18, 2021, 06:04:56 pm
content: Quote from: NiHaoMike on September 18, 2021, 05:49:37 pmAnd how about the neighbours?

author: Zero999
author_rank: Super Contributor
timestamp: September 18, 2021, 06:54:45 pm
content: Quote from: Berni on September 18, 2021, 05:25:51 pmThere has been a fall in electricity consumption by residential customers over the last decade, due to more efficient appliances, such as incandescent lamps being replaced with LEDs.That will reverse as electric cars become more common and the power distribution network will need to be upgraded to cater for it.

author: Berni
author_rank: Super Contributor
timestamp: September 18, 2021, 07:36:22 pm
content: Depends on the area-Here power consumption is going up because people are moving away from burning fuels to heat the house, now getting heatpumps to do the job. More and more people are also getting air conditioning where compared to before barely anyone had it (It does not get all that hot here to make them a must)Oldschool gas burning cookers are getting replaced by modern induction cookers that also use lots of power, while the gas one used 0 power.We really did not use electricity for making heat. About the only common use for it was hot water heaters and ovens.On top of all that it is common to run 230V for up to 2km down the whole street over just one set of wires. It is 3 phase and pretty chunky wires, but at some point the wire resistance still comes into the equation for the accompanied voltage drop.Electric cars are not all that popular yet, but places like Norway that does have a lot of electric cars really had issues with the amount of power they suck up. They had enough power in the grid to make it happen since they have heaps of hydro power, but the last mile low voltage distribution was not up to the job, causing voltages to plummet and light bulbs to dim.

author: Faringdon
author_rank: Super Contributor
timestamp: September 18, 2021, 10:16:19 pm
content: Thanks, you are all correct, but the thing that is being missed in the press is that GTI_based_solar is going to crash at some point........because when you have loads of people exporting solar to the grid via their GTI's...this tends to raise the grid voltage...and GTIs stop working when mains voltage goes up to 253VAC.The only way round this is for households to put their solar into a battery...and then this battery feeds their household loads via an inverter which is not grid tied, ie, not connected to the national grid.Its the only way, surely you agree?But the GTI industry is currently in denial of this.

author: Monkeh
author_rank: Super Contributor
timestamp: September 18, 2021, 10:18:01 pm
content: Quote from: Faringdon on September 18, 2021, 10:16:19 pmNo, because we're not your echo chamber.

author: NiHaoMike
author_rank: Super Contributor
timestamp: September 18, 2021, 10:22:08 pm
content: Quote from: nctnico on September 18, 2021, 06:04:56 pmThey're farther away so they'll see lower voltage. Looking at reference designs for universal input power supplies, they're tested up to 265V, some up to 270V.Since it's the peak voltage that determines the voltage seen by electronics, perhaps the solar inverters, if they detect the voltage going high, could start pushing more power on the lower parts of the sine wave and less on peak? It could be done in a controlled manner such that the harmonics would be of low frequency and unlikely to cause interference. Conversely, electronic loads without PFC would theoretically help the situation by pulling down on the peaks more than the same amount of load with PFC.

author: Cerebus
author_rank: Super Contributor
timestamp: September 19, 2021, 01:13:33 am
content: Quote from: NiHaoMike on September 18, 2021, 10:22:08 pmYou seem to be making the unwarranted assumption there that everything connected to the mains has an SMPS at the front of it. This is not the case.

author: Cerebus
author_rank: Super Contributor
timestamp: September 19, 2021, 01:28:49 am
content: Quote from: Monkeh on September 18, 2021, 10:18:01 pmAh yes, the "presumptive close" the trick of every desperate salesman out there.

author: NiHaoMike
author_rank: Super Contributor
timestamp: September 19, 2021, 01:46:48 am
content: Quote from: Cerebus on September 19, 2021, 01:13:33 amThat's true for an ever increasing percentage of loads. Aside from all the high tech devices commonly thought of as electronics, it also includes most LED lights, modern fluorescent lamps, inverter drive motors, and induction heating appliances.I'm also pretty sure there's a good reason why 265V or 270V is chosen as the upper test voltage for most universal input power supply designs.

author: Cerebus
author_rank: Super Contributor
timestamp: September 19, 2021, 02:47:07 am
content: And excludes motors and resistive heating elements in washers, dryers, ovens, stovetops, kettles, coffee machines, toasters, grills, most refrigeration etc. I think a few kW each for many of those kinds of loads (my kettle alone is 3.5 kW) rather tips things in their favour against the 5-200W each typical of most household appliances that have an SMPS in.

author: bdunham7
author_rank: Super Contributor
timestamp: September 19, 2021, 03:20:21 am
content: Quote from: NiHaoMike on September 19, 2021, 01:46:48 amI believe that the typical utility voltage upper limit in the US would be 252 volts (240 nominal + 5%) and the voltage tolerance for devices would be 264 volts (+10%) and that is for everything not just SMPS designs. However, grid-tied inverters are typically set to a nominal upper value of 264 volts, so they keep producing even if the utility voltage is exceeding their 5% tolerance limit. I don't know overvoltage curtailments are much of a problem elsewhere, but it hasn't happened to me yet.

author: Zero999
author_rank: Super Contributor
timestamp: September 19, 2021, 10:14:42 am
content: Quote from: Cerebus on September 19, 2021, 02:47:07 amHow does it not trip the 13A plug top fuse? Presumably that must be the surge rating.Quote from: Faringdon on September 18, 2021, 10:16:19 pmOr you could just turn on a water heater and air-conditioning to bring the voltage down a bit.

author: Faringdon
author_rank: Super Contributor
timestamp: September 19, 2021, 10:24:11 am
content: QuoteI think this is asking for too much customer participation.When people buy solar and a GTI, they expect to be able to profit whenever there is sunlight.......they cannot necessarily do that if they have a GTI connecting their solar to the grid....which everyone does, or most do at the moment.I also think GTI's cut off when grid voltage becomes >253VAC.(?)I think IMHO, we all agree that the Solar_GTI is in denial of the situation.

author: nctnico
author_rank: Super Contributor
timestamp: September 19, 2021, 10:38:27 am
content: Quote from: Faringdon on September 19, 2021, 10:24:11 amNo. If you would have followed the news a bit then you'd know the problem is well known and newly developed suburbs are typically fitted with a better grid connection. But that still leaves a large number of houses/buildings that have a less than ideal grid connection which may or may not be upgraded at some point. In the end it is a cost versus benefit calculation. Some people likely get the short end of the stick.

author: Zero999
author_rank: Super Contributor
timestamp: September 19, 2021, 11:52:27 am
content: Quote from: Faringdon on September 19, 2021, 10:24:11 amWith smart devices, the user doesn't have to do anything. They can communicate with the inverter and use up extra energy when necessary. Even if you don't have smart appliances, it doesn't take a genius to always set the timer on the washing machine, so it runs through the middle of the day, when the solar panels will power it.

author: Psi
author_rank: Super Contributor
timestamp: September 19, 2021, 12:34:48 pm
content: With electric cars driving new/cheaper batteries it will make more sense to store your excess solar energy locally, rather than push it into the grid during peak outs and pull from grid during off hours.Usually you don't get retail rates for that power, so it costs you extra money to pull it back out again later.If electric cars get cheaper so do power walls.

author: Jester
author_rank: Frequent Contributor
timestamp: September 19, 2021, 01:23:22 pm
content: Quote from: Faringdon on September 18, 2021, 02:04:39 pmI appreciate that at the small ends of the distribution system these high voltage conditions may limit how much an individual inverter can push back into the grid at a particular time. However looking at the bigger picture obviously the utility has control of the voltage and frequency. From my perspective having all these inverters gives us a better distribution of source power, many baskets instead of a few big ones.With electricity rates tied to peak hours, I don’t think to many Tesla owners are charging when they come home at 5pm, that would be foolish.

author: Cerebus
author_rank: Super Contributor
timestamp: September 19, 2021, 02:05:47 pm
content: Quote from: Jester on September 19, 2021, 01:23:22 pmAn assumption based on your domestic market that doesn't translate to a whole world picture. Some places have peak pricing, some don't.For instance, in the UK domestic market we don't generally have peak pricing although some alternative providers are now experimenting with it; we have an off-peak overnight tariff (typically midnight-7AM) that can be used for storage heaters and the like and have had that for a long time. Perhaps the canniest UK EV users are using off-peak pricing but I suspect most don't give any consideration to what time it is when they plug in to charge - the peak pricing disincentive just isn't there.

author: Jester
author_rank: Frequent Contributor
timestamp: September 20, 2021, 11:33:02 am
content: Quote from: Cerebus on September 19, 2021, 02:05:47 pmGood point, apparently (first google hit), smart meter deployment is > 40% worldwide, 67% in North America. First comes the smart meter followed shortly after with peak pricing, it won’t be long.

author: Cerebus
author_rank: Super Contributor
timestamp: September 20, 2021, 12:48:04 pm
content: Quote from: Jester on September 20, 2021, 11:33:02 amIt won't for the UK then because smart meters will never be universal here as there's a "right to refuse" enshrined in law so they just can't do it. If they tried to invent a new "you don't have a smart meter" tariff they would soon get pummelled (by the courts) for punishing people for exercising their rights.I'm actually a smart meter refusenik, for two reasons. (1) The ability to remotely extract usage patterns for individual households is a proxy for "when is this house unoccupied". When, not if, but when some bunch of organised housebreakers get their hands on this data it's obvious what will happen. (2) The ability to remotely cut off electricity. I don't want to be in the situation where someone makes a mistake about a bill having been paid or not and can cut me off remotely. If you have to send a body out to cut me off (a) I can stop them and say "no, you've made a mistake" (b) bodies going out is expensive, remote cutoff isn't - ergo eventually the time between "payment overdue" and "cutoff" will get shorter and shorter and the grace period you currently enjoy if there's a genuine mistake, or you're just desperately waiting for payday will vanish.

author: tszaboo
author_rank: Super Contributor
timestamp: September 20, 2021, 01:34:16 pm
content: Yes, this is an issue already. Belgium has great solar penetration, and it affects customers.That being said, we analyzed about 10K solar installations, with "big data", and only a few % of customers lost income more or less 50 EUR per year. This can be prevented if the DSO installs larger diameter cables (fat chance) or changes the feedline transformer turns ratio. Old transformers were installed so that the house closes to the feed line has as high voltage as possible. If you reduce that voltage, the issue becomes lesser.The extra energy can be used to generate apparent power BTW. Basically reducing the slip between the current and voltage. This thing costs a lot of money. Or orient the panels to "less than optimal" azimuth. West facing solar installations might generate less power, but it can do it in times, when it is actually needed.

author: richard.cs
author_rank: Super Contributor
timestamp: September 20, 2021, 02:10:27 pm
content: Quote from: Cerebus on September 20, 2021, 12:48:04 pmEverything I've read suggests that you can refuse to have one installed in the short term, but when your current meter reaches end of life (basically when the calibration expires) you can't refuse a meter change, and they are not obligated to offer you a dumb meter at that point.https://www.smartme.co.uk/customer-rights.htmlIn any case the law can and probably will change over time.

author: madires
author_rank: Super Contributor
timestamp: September 20, 2021, 02:13:11 pm
content: Quote from: Cerebus on September 19, 2021, 01:13:33 amBack in the 220 V era EEs were taught that PSUs should support a tolerance of +/- 10 %. So old devices (many with transformers) should be fine up to 242 V. BTW, in my case there are a few PV installations in the neighborhood (maybe 30 - 50 kW in total) and the mains voltage is around 236 V.

author: madires
author_rank: Super Contributor
timestamp: September 20, 2021, 02:19:41 pm
content: Quote from: richard.cs on September 20, 2021, 02:10:27 pmOver here you'll get a smart meter when your power consumption exceeds 6000 kWh per year or if you feed power into the grid.

author: themadhippy
author_rank: Super Contributor
timestamp: September 20, 2021, 03:17:03 pm
content: QuoteWithout a smart meter good luck getting the cheapest energy price from most suppliers

author: Gyro
author_rank: Super Contributor
timestamp: September 20, 2021, 07:48:25 pm
content: Quote from: themadhippy on September 20, 2021, 03:17:03 pmYes, it's become a condition that you have one fitted for some tariffs. It worked for me though, I got a free mains isolator and tails upgraded to 100A 25mm2out of it (you have to remember to ask the fitter nicely mind you).

author: Shivamraj243
author_rank: Newbie
timestamp: September 26, 2021, 10:49:53 am
content: you can also go to google

author: Faringdon
author_rank: Super Contributor
timestamp: October 10, 2021, 02:10:48 pm
content: Actually, this video,https://www.eevblog.com/2021/10/10/eevblog-1426-this-problem-can-drop-solar-output-by-20/..at approx 7:50, brings into question that GTI's can possibly deliver into voltages above 253Vac.This is above 230VAC +10%.So this would, in fact, kind of squash the theory that GTI's will all start cutting out when mains goes above 253V. It was also mentioned that the upper trip point may possibly be user programmable.......so this has flummoxed me.However, i am sure there is some regulation somewhere which says that GTIs (at least in UK/AUS/EU) must trip out at 230 -10%,+10%?The video does suggest that GTI's can possibly raise the mains voltage......which doesnt bode well for GTI's in a neighbourhood where there is no big battery bank to keep the mains voltage from rising away.

author: Cerebus
author_rank: Super Contributor
timestamp: October 10, 2021, 04:50:19 pm
content: It's almost as if someone slept though their year 1 lectures on Kirchhoff, Thévenin and Norton.

author: mansaxel
author_rank: Super Contributor
timestamp: October 10, 2021, 05:28:16 pm
content: Here, all new construction 1-family houses since 1973 or so (oil crisis) are required to be 3x10mm2+10mm2and 35A capable. Three-phase. Frankly, I'd be really cross with the power utility if my voltage was down at 265V. Hovering around 400 is more like it.We live close to a water tower, which has a priority power requirement, so we're very well connected, due to sharing the transformer with the water tower.I just got a new, smart meter, same style as in Netherlands. The law here is crystal clear; the power utility owns the meter and can swap it as they see fit.With this meter generation, the ability to measure power both ways is introduced. I can get one reading per second locally too, if I connect the right gadget. Which I will.

author: alexnoot
author_rank: Contributor
timestamp: October 10, 2021, 05:48:52 pm
content: Quote from: mansaxel on October 10, 2021, 05:28:16 pmI'm not sure if you're being serious, but the 253V mentioned is the voltage across live and neutral. Australia is a 400V country as well... At 253V L-N, the L-L voltage would be about 438V. The official voltage across Europe (and I'm guessing AU as well) is 230V +/- 10%, meaning between 207V and 253V. Obviously neither extreme is good in the long run, but that's the standard. In my neighbourhood in Norway I'm averaging about 240V, from data collected the past 90 days. My max is 249V, and the min is 236V. And there's literally no solar around here, so you can't blame that.Also, Faringdon has a habit of starting a ton of threads with somewhat insane arguements about everything and anything. I'm still waiting for him to finish his electric vehicle charger, the one with all the safety features and expensive components removed. Meanwhile he's saying Tesla's Powerwall will fail at 10 years due to cheap capacitors. So I'm not really sure what he's on about.

author: mansaxel
author_rank: Super Contributor
timestamp: October 10, 2021, 06:01:30 pm
content: Quote from: alexnoot on October 10, 2021, 05:48:52 pmOh, in part, but only as far as just before starting to point fingers at the part of the world that does not give residential homes the default of three-phase mains. That is something I usually blame Edison for, and is as close to "asocial thread-hijacking" that I'll go.Finally, I know next to nothing about electricks, but I can plainly see the errors in Faringdon's interpretation of perceived phenomena. Even with a loaded low voltage grid, the larger grid on the other side of the transformer is mostly going to be low enough impedance that local voltage surges are going to be eaten. And, coincidentally, a significant residential load in countries where people install solar is air condition, which will consume at precisely the times when solar is working at peak. I do concur that there are large local variations in this, and it is not unthinkable that problemscouldemerge. But a general inability to handle local production, no.