Avoiding being overcharged by your smart meter by using AC line filters.  - Page 1
Forum section: electronics / projects

author: Fflint
author_rank: Frequent Contributor
timestamp: January 07, 2022, 08:22:14 am
content: I believe it is a well established fact many modern smart meters measure highly distorted waveforms inaccurately. For those unaware I'll mention results of one study found errors ranging from +500% to - 40% with a waveform produced by a string of 30 household lights on dimmers (half led, half cfl).There was also a study done more recently that concluded the above results are "questionable", but they arrived at that conclusion by using waveforms "that meet maximum allowable THD"(according to local gov standard) . Of course if they used a lot less distorted waveforms they got a lot less error (up to 5% if I remember correctly). And they also added that "classic" resistive loads on the same AC line further improve on the measurement error and no one uses just non linear loads in their house right? (this was written in 2018 or so).Now in 2022 in my house I pretty much only have non linear loads including 75 led lights, induction hob, all appliances with electric motors use inverters etc. I haven't checked current waveforms I have (I'm waiting for CTs to arrive from China), but I'm pretty sure I'm being overcharged by around 10%~15%. (I did all the usual checks in the past)I imagine the error in smart meters measurements is due to not high enough sampling frequency plus the averaging method used. In my country (as well as in rest of EU I think) if you complain to the power company they will "recertify" your meter with pure sinusoidal waveform drawn by a resistive load.So I became interested in various filtering technologies. I'm not talking about those "save thousands on electricity" scam boxes that contain a tiny capacitor, but real series and parallel filters.Unfortunately based on what I read one needs both types of filters to cover two kinds of distortion. Voltage (distortion) sources (all devices that contain diode rectifiers and filtering capacitors) and current sources (all devices that switch on a very low impedance load for a very brief period of time such as many dimmers, led lights etc).Techniques for design of those filters are known. Also one would probably need some sort of overcurrent bypass of series filters in case one has a high power resistive load (electric flow water heater) that is used rarely.However, I'm starting this thread to ask if anyone already has designed and is using any filters like those I mentioned. Perhaps existing filters built to improve AC power supply quality could be used in some configuration.Or perhaps there are some creative low(er) cost solutions to improve individual electrical loads. For example led lights or central heating water pumps (tiny inverter driven). Those electric pumps are running 24/7 in winter. They are supposed to draw 20W~50W on their setting, but it is measured more like 200W (with two of them). Perhaps sticking an isolation transformer between them and AC line would help? I don't know. So what do you think?

author: Siwastaja
author_rank: Super Contributor
timestamp: January 07, 2022, 08:25:21 am
content: Quote from: Fflint on January 07, 2022, 08:22:14 amExtraordinary claims require extraordinary evidence, so maybe give references to the studies you talk about? Most definitely it is not a well established fact.This sounds like a typical case where you shouldn't waste time engineering something before you truly understand the problem - if it exists at all. Likely it doesn't.

author: Karel
author_rank: Super Contributor
timestamp: January 07, 2022, 08:48:47 am
content: Electronic energy meters’ false readings almost six times higher than actual energy consumptionhttps://www.utwente.nl/en/news/2017/3/313543/electronic-energy-meters-false-readings-almost-six-times-higher-than-actual-energy-consumption"The study, entitled ‘Static Energy Meter Errors Caused by Conducted Electromagnetic Interference’, arepublished in the scientific journal ‘IEEE Electromagnetic Compatibility Magazine’. The Van SwindenLaboratory (the Dutch Metrology Institute), which carried out a countercheck, has confirmed theseresults. The study was conducted by Prof. Frank Leferink (Professor of Electromagnetic Compatibility atthe UT), Cees Keyer (lecturer at the AUAS and PhD candidate at the UT), and Anton Melentjev (at thattime, a student at the AUAS)"

author: uer166
author_rank: Super Contributor
timestamp: January 07, 2022, 09:03:08 am
content: From the website you linked:QuoteAs someone who designs and certifies MID meters, both 3-phase and 1-phase, the above smells of BS, the designers certainly have allowed sufficient allowance for high harmonic content. There are afewcases where a lot of the meters in the field read extremely low when presented with a half-wave rectified load, namely the current-transformer based ones. I don't see how anything can read 582% high unless you're trying to defeat the device in some non-real-world edge case. Also, hall and rogowski? Seriously? The author couldn't have chosen anything more exotic than that, household meters are CT or shunt-based.I have found the actual paper scihub and going through it now, I suggest you do too to understand how the authors may have been mistaken (or not).

author: uer166
author_rank: Super Contributor
timestamp: January 07, 2022, 09:30:01 am
content: Really funny bit:QuoteAs opposed to uh, an Arduino and reusable seal??In any case, the paper has a lot of truth to it in a technical sense, but also has a lot of problems and misleading info IMO. Some of the issues are:They used a mechanical meter as their "reference" meter. Who says that that thing is able to read the high-bandwidth signals they put through it at all? I mean maybe it's not the smart meter that is +582%, but the mechanical meter is -582%It seems like they cherry-picked old crappy units that may not actually have had anti-aliasing filters, in which case, yes, you may get aliasing and an over-estimate of energy in very specific conditions.The condition was a extremely high distortion/harmonic load, that was relatively low power in total, without any resistive base load. Unless your entire house behaves like a 10kW CFL lamp on a dimmer, you can sleep easy. There is a reason why high-power electronics are required to have PFC, that is part of the mitigation for stuff like thisThey made no attempt to use a real reference meter/transfer standard as a reference. Even a simple digital power meter would have been more credible.In any case, none of the issues identified would be solved by AC line filters, most of them seem phase dimmer-related in some extraordinary conditions, so in context, this is a mostly made-up problem.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 07, 2022, 10:01:25 am
content: Big brain play: run your house off an inverter, supplied from an old fashioned SCR phase control. Now your whole house is as disgusting as a 10kW CFL on a dimmer!Tim

author: moffy
author_rank: Super Contributor
timestamp: January 07, 2022, 12:37:40 pm
content: Found this other article based upon the one referenced already:http://www.enmanreg.org/wp-content/uploads/2016/07/reported_meter_errors.pdfbut by:QuoteI can understand that:QuoteIf the integrator saturates, which they are prone to, then you could well get very high readings. A high crest factor can be a real issue, looks more like the qualifying waveforms used to certify meters do not cover a broad enough range of currents. Not saying that this is what is normal, but on the outer edges of possible.

author: Simon
author_rank: Unknown
timestamp: January 07, 2022, 12:47:55 pm
content: I sounds like apparent power being measured. And maybe it is time to switch the way electricity is charged to consumers and have the pay the same way as industry by the apparent power they use not the lesser real power and the apparent power had to be generated as well..... If we are to stick with sine wave supply from mechanical generators then we need to stop pissing away power on poor power factor. If people were charged for the impact of their cheap junk they buy they will soon start to choose better products and the cheap shit will disappear.Dave did a video on the power wasted by smoke detectors, the apparent power of a nations worth of smoke detectors was a significant number in the MW. As far as I am aware all power supplies over 1kW have to be power factor corrected.If more generators that use inverters appear on the grid I guess it will be less of a problem, although current delivered in short large peaks is hardly efficient anyway and will still require thicker wiring.

author: Marco
author_rank: Super Contributor
timestamp: January 07, 2022, 02:07:35 pm
content: You could try to get one of those big industrial PFCs (the passive ones) and test your home. You're not in Oz so it probably wouldn't be illegal.

author: madires
author_rank: Super Contributor
timestamp: January 07, 2022, 02:38:35 pm
content: Quote from: Simon on January 07, 2022, 12:47:55 pmEN61000-3-2 requires SMPSUs with more than 75W to include a PFC (may be passive).

author: Simon
author_rank: Unknown
timestamp: January 07, 2022, 06:22:30 pm
content: so what are the PF limits? the meanwell supply on my 3D printer is 0.5 PF according to some cheap power meter, it draws 350W

author: TheMG
author_rank: Frequent Contributor
timestamp: January 07, 2022, 06:23:17 pm
content: Even ASSUMING you're actually being slightly overcharged, the amount of money you're going to have to spend to filter your AC power back to a nice unity power-factor, sinusoidal current and voltage waveforms, is likely going to far exceed any money you save (if any at all).Also, no filter is perfectly lossless. You could actually end up increasing your power consumption and the amount you pay, just from the losses of the filter components alone!

author: TheMG
author_rank: Frequent Contributor
timestamp: January 07, 2022, 06:32:44 pm
content: Quote from: Simon on January 07, 2022, 06:22:30 pmIt's actually defined as a set of limits on the amount of each harmonic, rather than simply the power factor. But in order to meet the harmonic current limits you would very likely end up with a PF of 0.9 or better.I don't know the specifics of the regulation but I'm assuming it only applies to finished consumer goods and not to off-the-shelf SMPS intended to be integrated into a product or for industrial use? Maybe that Meanwell power supply was not intended for the European market at all? At 0.5 PF I would say there is zero power factor correction of any kind in that power supply and it definitely wouldn't be compliant on its own.Anyways, especially here in 120V land, large SMPS without PFC are rather inconvenient. 350W at 120VAC with a PF of 0.5 is 5.8A of current, which is quite significant when you consider standard circuit breaker size in homes and offices here is 15A. In other words, the better the PF, the more actual loads you can put on the same circuit without tripping the breaker. I have a Sorensen bench SMPS max 60V 20A that does not have power factor correction, at near-maximum load it will quite happily trip a 15A breaker on its own even though it's only drawing about 1400W input, which is a real pain in the butt!

author: TimFox
author_rank: Super Contributor
timestamp: January 07, 2022, 06:39:27 pm
content: On the regulatory front, what is thelegaldefinition of thebillableenergy (in W-hr) when the load is non-linear?The scientific definition is the integral over time of the product of voltage and current, where both of them are bipolar real-valued functions of time, not necessarily proportional to each other or in phase.(With a simple resistive linear load, that results in the usual measurement of mean power as the square of the rms voltage divided by the resistance, integrated over time to get energy.)

author: ejeffrey
author_rank: Super Contributor
timestamp: January 07, 2022, 06:50:58 pm
content: Quote from: Simon on January 07, 2022, 12:47:55 pmApparently power doesn't need to be generated. It doesn't consume fuel. However the generators, transmission lines, and transformers need to be *sized* based on apparent power. There are losses associated with apparent power but it is around the ~10% transmission and distribution losses. The main reason that utilities care about apparent power is not really the losses -- although they do care about that -- but the fact that reducing apparent power can avoid the need to build new or upgrade old infrastructure. It allows them to support rising demand by simply increasing generation rather than adding new power lines and transformers.QuoteThose smoke detectors are completely embarrassing and very lame design, but a few MW of excess apparent power in a nationwide distribution network is not really significant. That's no excuse for such poor power supply design, but it isn't really causing a major burden on the utilities. Especially since, while bad power factor, the load from smoke detectors is constant over the day. Poor power factor is basically the same problem as bursty demand. In both cases infrastructure cost and losses are set by the peak usage, rather than average.QuoteI'm not sure what you mean here, but inverters vs. mechanical generators is almost no difference for power factor. Power factor losses come from the additional I^2 losses in distribution and somewhat in the generator itself, but inverters also have conduction losses that depend on power factor. The one thing related to "inverters" that would improve losses from bad power factor is to have long range power distribution done via HVDC with AC inverters closer to the point of consumption. This reduces the distance that the out of phase / harmonic current is transmitted and thus the associated losses. This isn't anything magical about inverters vs. mechanical generators, it is just that the HVDC link is performing power factor correction. You could do the same thing with a motor/generator coupling.

author: madires
author_rank: Super Contributor
timestamp: January 07, 2022, 07:22:19 pm
content: Quote from: Simon on January 07, 2022, 06:22:30 pmhttps://en.wikipedia.org/wiki/IEC_61000-3-2

author: Jeroen3
author_rank: Super Contributor
timestamp: January 07, 2022, 07:39:24 pm
content: And this is only loads. Do you have a transformerless solar panel inverter?I have 8 enphase units on my roof, it'snightnow, the little DIN rail meter shows: 0.61A, 225.6 V, 5.5 W, 138.9 var,PF 0.03, 49.98 Hz.Imagine roofs and fields with hundreds of these things...

author: bdunham7
author_rank: Super Contributor
timestamp: January 07, 2022, 08:36:12 pm
content: Quote from: Jeroen3 on January 07, 2022, 07:39:24 pmDormant Enphase units have acapacitiveload which actually helps cancel out the reactive current from inductive loads.

author: Simon
author_rank: Unknown
timestamp: January 07, 2022, 09:12:46 pm
content: Quote from: ejeffrey on January 07, 2022, 06:50:58 pmi should know all this having just proof read my university module on the modern energy system but, oh yea, I proof read it and the tutor was insulted that I know more than they do.... that's how little is in the module as I am far from the expertwhat effect does poor power factor have on a generator? if it produces one AC cycle per rotation and the power factor is 1 then the load is constant as the generator rotates. If there are enormous peaks of current draw at the peak voltages then that is 6 positions in each rotation that will have extreme torque demands compared to the rest.Now if this is an inverter it just deals with it providing it can do the peaks, so my solar system is 4kW at most but has an 8kW inverter and at times when i am only generating say 1kW with 8kW capability it can deal with the poor power factor oaf a load, so if something in my house or a house nearby has poor powerfactor my inverter has more chance of dealing with it than a generator that may just end up producing a not so sinusoidal output as 6 times a cycle it hit a bit bump.

author: Kleinstein
author_rank: Super Contributor
timestamp: January 07, 2022, 09:42:49 pm
content: A poor power factor will usually lead to extra losses in the transformers and distribution cables. There is a difference between the pure phase shift part, e.g. from capacitors and motors and the nonlinear parts from SMPS without PFC correnction. The inductive and capacitive loads can cancel out before the transformer (at least before the 2nd layer) and when there is usually a inductive part (the transformer it self add some inductive part) there may be already capacitors at the transformer station, either fixed and sometimes switched.The nonlinear part does generally no compensate that well. Most of those bad supply are similar and take there peak current when the voltage is highest.Before PCs had PFC the mains in an office building was quite distorted with clipped peaks.The smart meters did show wrong reading in the test with a current that was way beyound acceptable limits. In addition this were mainly old meters that failed. The readings where relative high, but the absolute reading still moderate. The usually main consumers (e.g. heating, coocking, AC) have a much better PF and would not be effected.Ideally the meter should show a warning that the load is exceeding permitted limits on the harmonics. Quite often the users don't know when they have too much crappy equipment to exceed the limits and they should do something about it.

author: uer166
author_rank: Super Contributor
timestamp: January 07, 2022, 09:50:15 pm
content: Quote from: Simon on January 07, 2022, 12:47:55 pmThat is absolutely not what the paper claims. All the meters are designed to measure real power, which is actually easier than measuring apparent power since you don't need to do any RMS calculation math. There is no reason to measure apparent power unless you need to, since it adds complexity. The issues they found are some edge cases related to aliasing, meter bandwidth, and seemingly EMI.

author: Alti
author_rank: Frequent Contributor
timestamp: January 07, 2022, 10:35:55 pm
content: Relatedtopicon harmonics and smart meters.

author: Simon
author_rank: Unknown
timestamp: January 08, 2022, 09:04:46 am
content: The thing is power factor seems to cover a multitude of things the 3 main ones I can think of areChopped waveform (dimmers)extreme peaks ( "smoothing" capacitors)just plain shiftEither way I don't see how the generators cope, if there is a high demand for current that the generator cannot take but is trying to generate then it's going to be a problem. Why else do industrial loads get charged by power factor as well?

author: Kleinstein
author_rank: Super Contributor
timestamp: January 08, 2022, 09:33:17 am
content: The industrial customers get an extra charge for apperant power too, but with a considerably lower rate. This is to encorage taking measures to do the power factor correction already locally. Things can also vary locally. They are often also charges for the peak power (as this determines the needed size of the transformers and lines).The phase shift part is the easiest to deal with. There are usually some capacitors at the transformers to reduce the out of phase current, some a fixed and some are connected only when needed.For the waveform distortions part of this is compensated from other devices, like old incandencant lamps or heaters, that consume current proportional to the votlage. Induction motors also have a tendency to restore the waveform to a more sine shape. So while they add to the out of phase current, they also help with the harmonics and also a little with the peaks.The capacitors for EMI suppression and to compensate the phase shifted current also deal with much if the sharp peaks.So not all the crap on the mains has to go back to the generators. Other parts also participate.For measuring there is no big difference in the effort to measure the real power and the apparent power - especially not for the smart meters. The smart meters sample the voltage and current waveform and than do the rest numerically. At least some of the chips (e.g. ADE7753) provide both the active power and RMS values and even more info on the grid quality. Would be nice if the meter would also record those to show drop outs and other failures - the information seems to be there.

author: jonpaul
author_rank: Super Contributor
timestamp: January 08, 2022, 10:00:18 am
content: We have smart meters in USA and France, and they have closely followed our expected power consumption.The bulk of load is either resistive (haters), inductive (motors) or PFC corrected if over 75W.The Power transmission and distribution industry and ERPI, have researched these issues and coordinated the metering and power quality standards long ago.The smart and dumb meters are specifically designed to measure the true real power consumed very accurately regardless of PF or current wave.Government regulations require the metering accuracy and compliance testing.Thus, I am skeptical of the OP premise that smart meters can be overcharging or that a line filter will change the KwH readings.Does the OP have any specific evidence (other than weblinks) that support his hypothesis?With Kind Regards,Jon

author: Karel
author_rank: Super Contributor
timestamp: January 08, 2022, 10:20:05 am
content: Quote from: jonpaul on January 08, 2022, 10:00:18 amHave a look at the attachment.

author: Fflint
author_rank: Frequent Contributor
timestamp: January 08, 2022, 01:53:30 pm
content: Wow, I'm away one day and there is almost 25 replies arguing over aproven factrather than the key question :how to filter distorted waveform to avoid the metering errorPower factor has nothing to do with it. Modern meters measure the power factor correctly. The problem is most likely(in the order of importance) with the type of the measuring device (hall sensor, vs Rogowski coil vs CT), sampling frequency and the averaging method.The studies I was talking about were both linked in this thread. First the university of Twente one, which no doubt had some issues including one that they used an analog meter for reference. Then the other (Polish) study that concluded the Twente guys results are "questionable", but if you read this study it actually supports the Twente guys results corrected by - 5% (the guy that did the Polish study did use a proper certified lab meter and he found out the old mechanical meters have an error of - 5% for his tested waveforms). He also used waveforms with THD "in accordance with the local standard" and found a smart meter error around 1%. Surprise, surprise, he used a lot less distorted waveforms and he found out the error is less pronounced!The key point of the Twente guys study is that they obtained the horrible waveforms by using normal loads people have in their homes. Led lights, CFLs and dimmers. Then he went on to conclude if one has one or two led lights running a resistive load like a kettle, an oven, or incandescent lights it will correct the waveform so the error is practically zero. When he did write that in 2018, perhaps people did have LEDs, and incandescent lights on the same circuit as ovens and kettles. Now I already mentioned I have 75 led lights (not counting high power external floodlights) in the house and almost no other linear loads. So at best the total error found by Twente guys should be revised lower not debunked.Both studies came out in 2017/2018. No one make any contrary findings I know about. So it is a fact. Now we can argue about it in next pages of this thread or we can focus on finding a solution.uer166as you design and certify meters I would be very interested in if you could tell us what sampling frequency meters typically use. There is a way of making an accurate meter that has low error even with distorted waveforms, but the amount of allowable distortion is specified in local standards and that's what meter designers design meters for. If we ask that they design them better how do we specify the limit of allowable distortion!? One could even say meters are fine, it is the people that use shitty non linear devices that emit conducted EMI in levels that far exceed the standards.And this is, to some extent my point. One can't complain to a government regulator that the metering device is inaccurate if one feeds it a waveform outside its design parameters.Therefore I'm looking for filters.There are various kinds of filters, more or less expensive as well as using isolation transformers etc. I'm very interested in finding out about anything that could help even with just individual loads.As mentioned previously, I have central heating pumps that run 24/7 in winter("smart" inverter driven) . Then there are LED lights(75 internal, and around 10 high power external) . I could put those (most offending) loads on separate circuits and build a filter. That's what I'll do once I have a way to measure the waveforms accurately. Until then I'm asking for additional ideas.

author: Siwastaja
author_rank: Super Contributor
timestamp: January 08, 2022, 03:01:41 pm
content: Quote from: Fflint on January 08, 2022, 01:53:30 pmNo! There is no proven fact! You clearly don't understand what "proven fact" means. All that has been shown is that at certain point in time, certain un-named meters showed wrong values in presence of very spiky current with dimmers. Which is interesting, and the paper was interesting; I have a scientist background myself and have published papers. Specifically, the 107Hz indication was mind-blowing, and clear indication that particular meter is misbehaving. But still, you arevery likelymisinterpreting the situation. Because people care about money. If it was really that wide-spread, it would have been widely noticed and discussed already.And it'sexactlythe right thing to discuss! Existence of problemisthe key fact in any problem-solving case; playing your X-Y problem games isn't.Because solving a problem which shouldn't exist, and very very likely doesnotexist, in the first place, is wasted effort. If the problem exists, it should be fixed where it is; working around it is more expensive.If the problem does exist, then authorities should be involved and the meters fixed.It's a real possibility that some meter series (the paper specifically shows those based on Rogowski coil; and I have to add to that, Rogowski coil itself does not have such limitation, it's an issue in the signal processing chain) have this problem with just that specific dimmer load profile. But does your meter behave that way, and even if it does, do you have such load profile?I guess you are completely on wrong track, and you can throw a tantrum of us not being helpful, but that only throws you further on the wrong track. You need tostartby proving the existence of the problem, otherwise there is nothing to design filter for.I agree with you that arguing about it is waste of time. So start your work quickly, but start from the right premise: measuring the problem you are going to solve. Demonstrating the problem should be easy to do: just turn on all the LEDs and CFLs and other supposedly problematic loads, and look at the meter. Compare to the expected consumption based on the bulb ratings - they are not accurate ratings, but enough to give you the ballpark. Can you do that?

author: uer166
author_rank: Super Contributor
timestamp: January 08, 2022, 05:15:36 pm
content: Quote from: Fflint on January 08, 2022, 01:53:30 pmYeah I don't agree here at all. The papers looked at some very specific and most likely hard to reproduce edge cases (including seemingly literally broken meters at Siwastaja pointed out). Just because nobody wasted time to debunk, or at least put some context in front of those papers, doesn't mean they're fact. And even if they were fact, it doesn't mean that they're applicable to your situation, 99.99% chance they are not. Do you have a 2011-era smart meter? Do you have the exact same kind of LEDs and dimmers that the paper used? Do you literally not have a single other load except for those?To satisfy your curiosity: modern Sigma-Delta simultaneous sampling ADCs would run at somewhere around 2~10kHz Fsamp, with antialiasing filter cutoff set to maybe half or less of Fsamp. You could definitely still havesomealiasing since it's not a whole decade or two below, but the resultant error would be small in absolute terms. Even then you'd need the sampling frequency to somehow match mains exactly for this to happen and not average out, which in real life would be impossible over the long term. Fsamp is not usually synched to mains (but RMS calculation windows are to avoid spectral leakage).The much bigger and more annoying issue is making CT-based meters that can tolerate having ~60A DC current put through them, and still measure to 1% accuracy or whatever. Another one is bad power factor (linear only: inductive or capacitive), since it requires tight matching of phase delays in filters, or accurate calibration of those delays. But we're talking about +-1% here that is required per MID standard, not the ridiculous numbers you saw in the papers you posted.

author: uer166
author_rank: Super Contributor
timestamp: January 08, 2022, 05:20:46 pm
content: Quote from: Fflint on January 08, 2022, 01:53:30 pmEverything has an envelope, and everything will break eventually. If your microwave has a hole in it and it irradiates the meter, do you expect it to meter accurately or work at all? Modern meters are extremely robust and can handle great abuse, including surges, external magnetic fields, horrible mains waveforms, static discharges, etc etc etc.I recommend getting some current clamps, and diff probes, and measuring your mains waveform consumption, just for funsies. I understand that you can't drop $30k on a reference meter (which is what the authors of the papershouldhave done), but it doesn't mean you have to be as janky as them.

author: rstofer
author_rank: Super Contributor
timestamp: January 08, 2022, 05:42:16 pm
content: Quote from: Simon on January 07, 2022, 06:22:30 pmIn industry, we pay a penalty if the power factor at the end of the billing period is less than 0.8. But it's only about $1000 on a bill that is in the multiple 10s of thousands of dollars. On a big system, you can't do anything to correct pf for $1000/month. Just smile and wave!

author: bdunham7
author_rank: Super Contributor
timestamp: January 08, 2022, 06:05:26 pm
content: Quote from: rstofer on January 08, 2022, 05:42:16 pmFor inductive motor loads, fixed capacitor banks that parallel the load are simple and quite effective even with variable loading because the PF of the motor improves with load. Sometimes they are worth it just to reduce the voltage drop in the wiring. There are all sorts of products just for this purpose. I don't know what the payback period would be, but in my experience the demand (peak) charges were way more than any PF levies.https://www.eaton.com/us/en-us/products/low-voltage-power-distribution-control-systems/power-factor-correction-capacitors.html

author: ejeffrey
author_rank: Super Contributor
timestamp: January 08, 2022, 07:21:21 pm
content: Quote from: Simon on January 08, 2022, 09:04:46 amGenerators cope the same way anything else does. The voltage is set by the magnetic flux and the current is whatever the load draws. Industrial loads get charged for poor power factor for two reasons: the increased transmission losses and because the transmission equipment is mostly limited by current and thus apparent power.Think of it this way. If you have a 16 amp / 230 V breaker in your house and you have a load that draws 10 amps but only consumes 1 kW. If you want to plug a second one in it will exceed the circuit current limit. You can't plug both in without upgrading the circuit or adding a second one. If the loads were power factor corrected they would draw under 5A each and could operate on the same circuit. To the power company, your excess apparent power draw prevents them from selling power to your neighbor unless they upgrade the transmission lines and transformers.

author: Fflint
author_rank: Frequent Contributor
timestamp: January 08, 2022, 09:42:47 pm
content: Quote from: Siwastaja on January 08, 2022, 03:01:41 pmYou assume that, but if the error adds up to let's say 10% of your usage that is extremely difficult to prove. Also as I stated before meters are certified for maximum allowable THD and devices used in our homes are not.The Twente team used 8 different smart meters. 3 - 3 phase and 5 single phase. It is true they didn't give out models (I wonder why not), but if you look you'll find a high resolution photo of their setup herehttps://www.researchgate.net/profile/Bas-Ten-Have/publication/337229022/figure/fig1/AS:970012051378189@1608280303753/Ten-static-meters-placed-in-series.jpgto hopefully recognise some meters if you want to.Quote from: Siwastaja on January 08, 2022, 03:01:41 pmBut, as I said before, if the usage error is a result of your loads resulting in higher THD than the norm allows then whose problem is it really? The authorities that are supposed to ensure the meter is able to accurately measure waveforms that comply with a standard or people's that use devices that cause the waveforms that exceed the distortion specified?Quote from: Siwastaja on January 08, 2022, 03:01:41 pmI can only believe what I read in a published scientific study. You are correct there are certain issues with the Twente study. Here you have a link to a much better Slovak study of the same thing done in 2021.https://link-springer-com.libproxy.viko.lt/article/10.1007/s00202-021-01365-8?error=cookies_not_supported&code=1af7722f-9d29-4015-9500-ccedc905263etitled "Contemporary electric energy meters testing under simulated nonsinusoidal field conditions". They did find errors as high as 37% in I quote "state of the art smart meters".Quote from: Siwastaja on January 08, 2022, 03:01:41 pmYes I can, and I did with my central heating pumps. The datasheet for the pump has a chart that shows power consumption at each setting (there are 6 settings, 3 constant pressure, and 3 constant flow). I set the pumps to the lowest setting. I switched off all the circuits in the breaker panel other than the pumps overnight and I took readings before I went to bed. Then in the morning. Instead of few tens of watts the load registered was close to 200W.This is just one example.There was time when I tracked this quite carefully, but eventually it required more effort than the money spent on the excess electricity was worth and I gave up. Then recently I found out all this research about meter errors with non linear loads. I'm also building a PV setup and electricity goes up in price by 50% next year in my country. So I became more actively interested in not being overcharged.Quote from: uer166 on January 08, 2022, 05:20:46 pmI don't even blame the meters (that much) if the loads truly generate such chopped waveforms.When the CTs I ordered arrive beginning of Feb I'll record loads waveforms and I'll find out if what I'm seeing is due to distortion, or error at the lowest measurable current or something else.For now I wanted to see if others are interested in the same thing. If others found problems and solutions I could make use of with smart meters.Quote from: uer166 on January 08, 2022, 05:15:36 pmOK, fine (about old meters). How about the 2021 study I linked above?As for my smart meter, is it a 2011 era meter? Yes, actually it has been about 10 years since I bought the land and I had power installed. So the meter quite literally is a 2010/2011 model(Apator 16ec3r). There are lots of people with such "old" and much older meters. When I was renting a flat in the city (5~6 years ago in UK) it had a mechanical meter that looked like it could've been 30 years old. People don't upgrade their meters unless there is a reason for it. However, my meter will be upgraded once I finish my PV setup as the power company requires a different model for bi-directional billing (despite my model supporting that).As for my loads I did describe them pretty well in this thread. I literally have two linear loads in my house. One is a well water pump,the other is a flow water heater. They see 20 min of usage per day if that much. Everything else is literally LEDs (most of the time 1 of the 3 phases has only LEDs, the other 2 have a mix of LEDs and switched power supplies). In near future I'll be adding a transformerless PV inverter too.Quote from: uer166 on January 08, 2022, 05:15:36 pmIt is interesting. I definitely would prefer a meter with Fsamp closer to 10kHz than 2kHz. Unfortunately, one has no choice in the matter. If it measures pure sinusoidal waveform with a resistive load correctly it meets the norm and that's it. You call the 500% results "ridiculous". No one is expecting errors of this magnitude in real life. 10% is a lot if it is across a year of use. The other issue you mentioned might very well compound with the first. If I'm reading the documentation of my meter correctly the lowest current it can measure is 250mA. That's 60W load at 240V. What if I had 3 30W loads each on its own phase? (lets assume linear for simplicity's sake) Will it register them as 3*60W continuous? Or will it miss them? Either way it is quite an error over multiple days and months. If I had a 3 phase PV setup and in winter during overcast sky it would produce 150W split across 3 phases would my meter show 0? Perhaps. And I haven't even started talking about non linear loads of the kind discussed in the research papers linked.

author: Siwastaja
author_rank: Super Contributor
timestamp: January 09, 2022, 10:03:38 am
content: Quote from: Fflint on January 08, 2022, 09:42:47 pmBecause they do not trust their own paper, and/or their higher-ups in the university management do not trust it, because they fear lawsuits they can't win, and they don't also truly believe the matter is important. On the other hand, publishing a paper is a way to get funding for the department, so why take the risk? This is how research really works: come up with something interesting, don't waste too much effort on it (your personal goal might be publishing 10-20 papers every year), make it good enough so it passes the journal standards.The fear against publishing product names is a tell-tale sign of mediocre science. It's everywhere. I have seen lot worse, but also lot better.Another sign is the "root cause" section which doesn't talk about root causes at all, just briefly mentions the existence of Rogowski coil. Root cause analysis is hard and tedious. Likely the team doesn't have the suitable experts. If this was a plane crash killing 300 people, root cause analysis would look quite different.Third is, they don't have a reference at all. The "reference" is just an arbitrary type of commercial meter, not proven to give correct results at all. This is understandable, because a real reference unit would be expensive, and proving its reliability yet more work.And don't get me wrong, I'm not saying this is bullshit or fake science. I appreciate the work, but you have to understand the context. This is just everyday reality how science works. The sole idea of the publication is to trig interest in the subject, to make someone with more experienced scientists, much more resources, and better trust in their own science, to repeat the measurements - and provide the brands and models of the tested products.It's common to hide the product names, but it's not some kind of standard that is always followed. I have seen papers regarding commercial off-the-shelf li-ion cells which identify the exact brands and products.I remember a scandal here maybe a decade ago when a university published a study that all Vitamin D supplement brands except one have significantly too little Vitamin D in them. In the end, it turned out their measurement was just completely flawed, and the products were fine - except the one which had too much.It's consideredproven factonly after it has been independently repeated, verified and discussed.

author: Siwastaja
author_rank: Super Contributor
timestamp: January 09, 2022, 10:07:58 am
content: Quote from: Fflint on January 08, 2022, 09:42:47 pmOK, this is indeed interesting.1) You are 100% sure there are no other loads? Did you let your refrigerator and freezer warm up during night? Can you repeat the same with the circulation pump turned off as well, to verify zero reading? And I mean, turned off at the pump, not at the breaker - sometimes house wiring contains surprises like undocumented branches.2) What does it mean to have "load registered to 200W"? Is this load number reported by the meter in Watts? Or did you calculate it by (morning_kwh - evening_kwh) / hours_between_readings? The latter should give you the correct result.

author: Simon
author_rank: Unknown
timestamp: January 09, 2022, 12:51:28 pm
content: Quote from: ejeffrey on January 08, 2022, 07:21:21 pmIt's worse than that. Take for example a load that draws power 50% of the time. To achieve the same average power draw the wiring sees twice the load, this is because you now pull twice the current 50% of the time. now I assume that so you had I^2 losses, now you have (2I)^2 losses for half the time. So lets say that the average power is conducted un 1/3 cycle pulses, now you have 3 times the loss. Now think of things running off rectifiers, when that smoothing capacitor charges, how long does it charge for? less than 1/10 of the cycle? whoopsI don't know what this does to a circuit breaker, I don't know if their operation is thermal but obviously like the rest of the system they take a pasting.I assume such extraordinary peaking on the line will drag the voltage down at the peak.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 09, 2022, 01:25:28 pm
content: Well yes, the circuit breaker just sees whatever RMS current is flowing.If the load draws power at 50% duty, the RMS is sqrt(1/50%) ~= 1.4 times higher than the same power draw at PF=1. So the PF is 0.7 in this case.Mind, PF is usually averaged over some cycles, not a long period, so we wouldn't normally claim that a resistive heater has a terrible power factor! If we allow such a definition for a moment, however, this does indeed work out the same way: the heater might be doing say 750W average, but it's doing it in gulps of 1.5kW or whatever, and so has a PF of 71%.Anyway, when this occurs within a cycle, as with SCR phase controllers or cap-input rectifiers, the traditional measure of PF will indeed show the same difference. Mind that it's weighted by the power available at any given instant: PF suffers very little indeed if you remove the flanks near zero crossing, but suffers greatly if you chop off some of the peak.And yes, most power is a bit flat-topped for this reason.Digression:A breaker takes some time to respond thermally (minutes to seconds, depending on overload). That response time actually serves as the averaging period over which we measure power factor, for purposes of breaker rating. We could have a 30A heater doing an every-other-cycle modulation pattern, or even on and off every second or so, and still operate apparently safely into a breaker nominally rated for 20A.This isn't problematic for safety purposes, AFAIK; in-wall wiring heats up in exactly the same way as the breaker does. Albeit at different rates. It could be that some connections heat up much faster (say those shove-insert / spring blade connections some receptacles have -- varies by locality!), and thus reach higher peak temperatures, experience more oxidation and cycling, and eventually open up and melt and arc. So, that conclusion does depend on nothing being more sensitive, over shorter time scales, than the breaker. Which maybe isn't a great bet, but should be an acceptable assumption with approved wiring.AFAIK, instruments measure PF per cycle, or over a window of some cycles. You'd get a better representation of behavior like this, from the peak/average consumption, or crest factor or the like, on a PQA.Tim

author: uer166
author_rank: Super Contributor
timestamp: January 10, 2022, 03:01:24 am
content: Quote from: T3sl4co1l on January 09, 2022, 01:25:28 pmYeah it's actually the exact same window that RMS values are calculated from, since PF = Power/(RMS(I)*RMS(V)). The minimum required is one full AC cycle, any less and the RMS value for that signal does not exist. I've seen it done over a window of one second (50 or 60 cycles) that is synched to mains.The energy is of course accumulated at the ADC sampling rate, and within a single AC cycle you can have both positive and negative energy flow into the accumulator when you have an inductive or capacitive load. This presents interesting challenges when meters implement separate "imported" and "exported" energy, since there is again a fundamental minimum of one AC cycle to determine the net energy flow direction. If you have a single "net" accumulator then no special handling required.Other cool thing is some meters operate entirely in the frequency domain: you take the FFT of all voltage/current harmonics over some window, and calculate power with some math kung-fu by multiplying voltage and current harmonics. I really don't like this since it's not intuitive compared to a simple integral of I*V samples, but it is cool. Anyway, this has nothing to do with OP's problem but I find this stuff exciting so

author: uer166
author_rank: Super Contributor
timestamp: January 10, 2022, 03:31:37 am
content: Okay so re: some notes for that second longer paper (Contemporary electric energy meters testing under simulated nonsinusoidal field conditions)QuoteI can totally believe the above, in fact, I don't see how modern digital meters can be any less accurate than the old ones, in general (especially with nonlinear loads).And:QuoteThe absolute worst error above was ~+8%, when the vast majority of meters was much less than that. The Class 2 meters are allowed up to 6% error in those conditions, so TBH it's not too far off, and not worth losing your sleep over that extra 2%.Other random points I gathered were:They injected 10kHz current waveform as a load. This is well beyond the BW of any 60Hz meter, soThe quoted >60% error was forreactive power, not real power. Residential users don't get billed for reactive power. Moreover, in certain condition, you cannot calculate reactive power accurately when using CTs for current measurement. This is a fundamental math problem (CTs can't measure even harmonic currents), not a accuracy/resolution/whatever problem.All in all, that second paper, which is substantially more thorough and believable, would lead us to believe that this is a non-issue, even with special "engineered" waveforms designed to defeat the meters. They still use a "meh" reference meter, but it is a massive step-up from a mechanical one.

author: Fflint
author_rank: Frequent Contributor
timestamp: January 10, 2022, 06:43:55 pm
content: Siwastaja, I don't disagree with you regarding the Twente study. However it served its purpose it highlighted the problem and other teams looked at the issue too.Quote from: Siwastaja on January 09, 2022, 10:07:58 amI'm as sure as one can be. I guess 99%?. My fridge/freezer is fine without electricity if it isn't opened for 7h or so. It is a new build house I was involved with building every step of the way. I didn't watch the electrician put in the wiring, but I have the schematic. I will be 100% sure when I have the CTs arrive and I measure the waveform right in front of the meter and compare with the readings.Quote from: Siwastaja on January 09, 2022, 10:07:58 amI compared the readings before I went to bed, and then first thing in the morning (I even took pictures back then). It shows usage to 1/10th of a kWh.Also with this meter it is possible to "read" current usage by measuring the time between the "ticks". It blinks the led every so many watt-hours. I can't currently remember how often (this was over a year ago). I spent lots of time doing that, switching off/on various citcuits, remeasuring etc.Quote from: uer166 on January 10, 2022, 03:31:37 amThe point is not that modern meters are less precise than old ones, but that with high use of non linear loads creating choppy wavorms there is a significant error. You mentioned the highest error was 8% while 6% is allowable. Firstly, I didn't realise 6% error is allowable. If it is, that is less than ideal.However, the purpose of the study wasn't to quantify actual error possible in real life with realloads. The goal in my opinion was to show that with non sinusoidal waveforms the meters show not insignificant errors.Now another team should measure waveform that happen with actual use of dozens of LEDs and lots of other "modern" loads. Then see how meters fare with those waveforms.Regarding your critique that injecting non sinusoidal waveforms with 10kHz frequencies into the ac line is unfair to a smart meter than usually handles 60Hz (50Hz here). In my opinion it is not a matter of fairness, but wmthe studies are bringing us closer to understanding if we are being charged correctly for our usage and generation. I can think of many loads that generate harmonics in tens of KHz in current as well as voltage (not at the same time of course, it is usually one or the other depending on what kind of load is it).Also If my meter had an error of 8% (overcharging on usage and again under measuring on PV generation) I could loose 16% total if my PVs cover 100% of my usage. That in monetary terms is enough to think about what one can do to fix that on one's end.I only use the 8% as an example. Currently what the true error is, is anyone's guess.I think, as the cost of electricity becomes even more bonkers considerations like this will become more and more popular. Perhaps I should ping this thread in 2 years time. I bet there will be more interest in filtering etc. Perhaps there will be more research by then. Also, as time goes by more and more people will have houses that contain only non linear loads that try to limit their power use by pulling power in very short time steps (possibly at or even below the current detection limit). Then they will get readings that make no sense.This is just an anecdote, but imagine my surprise when there were 2 months during which I had to use an electric resistive heater. I set up a simple power measuring device (plug with WiFi) not to be surprised by the bill. I used up around 30% more electricity during those two months. Then once the bill arrived I paidlessthan usual for the time period(my bills are bi-monthly) Not by much, just few percent, but still this was bonkers. (The readings are not estimated, a guy from the electric company comes every month and physically reads the meter). Also I work from home, my usage is very consistent and predictable beyond the expected seasonal changes.I'm mentioning the above not as proof, but just to demonstrate the kind of inconsistencies that do happen.

author: Siwastaja
author_rank: Super Contributor
timestamp: January 10, 2022, 06:56:27 pm
content: OK, you might be into something.This would make an interesting class action lawsuit. IMHO, meter manufacturers cannot hide behind the claim that some types of loads are "not within specifications", if these loads pass the regulations i.e. are legal, as the intended purpose of an electricity meter is to measure electricity used by such legal loads.If I had such case, I would just add an illegal outlet before the meter. Yes, stealing, yes, illegal; exactly like installing a meter that meters incorrectly. If you made sure you "steal" exactly the same amount the meter miscalculates (by installing a good reference meter), it would make a pretty interesting lawsuit because you could logically argue you are not stealing!A more serious note, just file a complaint and request a new meter to be installed. See what they have to say. It's possible this is a known issue with a specific brand of meter and they just replace them whenever someone complains.

author: Kleinstein
author_rank: Super Contributor
timestamp: January 10, 2022, 08:47:27 pm
content: The load they used in the first study was actually beyound the limits for a legal load (too much power for phase for phase angle modulation).AFAIR some of the meters that had the most issues were old designs, no longer in use with some known issues with extreme loads.The newer, more detailed study showed lower errors and only 1 meter 2 % higher than the spec limit (6% allowed vs actually 8%). I am nut sure if this includes to possible error of there reference meter. With most tested meters reading high, there is a chance that there refence meter was reading low. So part of the error, if not most could be from there ref. meter. This same problem applies to the old study. It could very well be that the old analog meter was reading low - AFAIK the limits there are much wider.The relatively large error was for a pure high distortion load, which is not very common. The regulation are so that the larger loads (like the PC, TV, electric kettle, microwave, and even LED lamps) need to be more well behaved.The classic incandecent lamp with phase angle control in the first study is hardly used any more.So you may get up too 6% over charged on a small part (maybe 5% usually less) of the consumption, but not on the main part.It is also that this it the worst case error. Some meters will also charge to little.

author: thm_w
author_rank: Super Contributor
timestamp: January 11, 2022, 12:08:11 am
content: The reference meter ENA330 from Elcom:https://fei1.vsb.cz/kat410/studium/studijni_materialy/pmd/Spolecne/Ena330_manual.pdfQuoteThey claim the i200 is accurate within 0.5% when the actual spec is 1% + 0.5A:https://www.fluke.com/en-ca/product/accessories/current-clamps/fluke-i200i200 has bandwidth of 10kHz. But ENA330 bandwidth is only 45Hz to 2.5kHz right? Is it valid to compare 10kHz injected signals?Attached is another paper where they use the ENA330 and measured a few percent low compared to their reference meter (Schrack LZQJ-XC).

author: uer166
author_rank: Super Contributor
timestamp: January 11, 2022, 12:49:02 am
content: Quote from: thm_w on January 11, 2022, 12:08:11 amI don't think so. Unless the reference and DUT meters have the exact same frequency response, any signals that are outside of either one of the meters' BW are not valid for comparison. I really don't get the point of this experiment since real energy at that high of a frequency is minute anyway. And of course, as a customer you're actually ahead here since you get it for free.There's been a lot of talk with very little data, it would be cool to get to the bottom of the issue and see who is wrong and how. Papers are cool and all but they have absolutely nothing to do with OP's situation.

author: Fflint
author_rank: Frequent Contributor
timestamp: January 12, 2022, 08:15:51 am
content: Quote from: Siwastaja on January 10, 2022, 06:56:27 pmThey have a complaint procedure that involves taking the meter away and recertifying (with a nice resistive load on a pure sinusoidal waveform Im told). If they find issues. They don't tell you the magnitude of the error. They just correct it or they install a new meter and that's it. You may have been overpaying for years, but you'll get no money back. However, if they find the meter is "fine" they charge you for the labour of recertification. So it makes much more sense to get to the bottom of it on one's own firstI'm in a middle of building a PV setup and as a part of registering it they will swap the meter for a different model so if this is indeed a dodgy unit it will help. However, if this is distortion etc. the new meter may be better or worse.My CTs should arrive in few weeks. It is very likely I'll have plenty of time before they swap the old meter to make measurements.Quote from: uer166 on January 11, 2022, 12:49:02 amDo you know a youtube that has a channel titled "Mr Carlson's Lab"? He has just uploaded a video of repairing a coffee machine with a SMPS. That coffee machine is broken, but even before it broke it emitted huge amount of (conducted) EMI in the range of hundreds of kHz. The owner noticed it, because he happens to repair old radios. He also found out it is not a simple case of a circuit emitting EMI into surrounding space, but that it uses the AC feed as a huge antenna (he checked this by plugging it via an isolation transformer with an rf shunt).So here you have an example of one device emitting signals in hundreds of Khz range into AC.All I'm saying is that the 10kHz test wasn't supposed to be an approximation of typical usage, but all sorts of scenarios happen. Sometimes for months on end.Quote from: uer166 on January 11, 2022, 12:49:02 amWell, there is no data, because the title of the thread isn't "I think my power meter lies". I was attempting to make this not about my particular situation, but a whole class of problems and solutions. You're not convinced that it is indeed a problem. That's fine. Maybe that changes in future when more studies come out, or data is captured by amateurs.Either way the subject of filtering AC distortion is an interesting one.

author: richard.cs
author_rank: Super Contributor
timestamp: January 12, 2022, 09:52:41 am
content: Quote from: uer166 on January 10, 2022, 03:31:37 amCTs can't measure DC, so a half-wave load (which contains both DC and even harmonics) would measure incorrectly, but that does not mean the even harmonics cannot be measured. 100 Hz, 200 Hz, 300 Hz, etc. (120, 240, 360 for the 60 Hz world) pass through a CT just fine.

author: Kleinstein
author_rank: Super Contributor
timestamp: January 12, 2022, 10:16:22 am
content: The new smart meter circuits in principle have the ability to check the power quality and detect cases with excessive crap on the voltage (e.g. bad inverter in the neighborhood) or extreme distorted current (e.g. poor consumers or bad PV installation) or brown outs with dropping supply voltage (e.g. overloaded transformer, thin lines). It is a shame that they not at least show an indication of the power quality.I don't think the chance of getting significantly overcharged is high. The tests with the low load with highly distored wavefrom may be off by a significant percentage, but this is still only low power and thus little money. In the sum the current waveform is usually still pretty good and the performance in the extreme cases is not that relevant.The extreme case would mainly apply with a broken, non compliant PV installation, possibly with a neighbor. So a shame the meter would not warn about this. Still this would be a rate case.The lower the discrepancy found, the less attentions the studies get - more like the worst one get the most publicity.There are cases when a new smart meter reads higher than an old style mechanical, but this is likely with an error with the old one.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: January 12, 2022, 03:03:09 pm
content: Quote from: richard.cs on January 12, 2022, 09:52:41 amNot completely. If the current goes to zero inbetween, and the L/R time constant of the CT + DCR + burden resistor is adequate, it will read just fine. This normally requires a diode though (to get the "off" direction L/R much shorter than "on"), so is probably a special case.Other than that, some DC can be tolerated, in which case the AC waveform and Vpp will be correct, but the baseline obviously won't. Not sure offhand what saturation current mode mains-frequency CTs have -- it could be as low as some 10s of mA, making this quite an important discrepancy, given most loads are much more than that!Tim

author: Kleinstein
author_rank: Super Contributor
timestamp: January 12, 2022, 05:04:18 pm
content: The current transformers should be resonable tolerant to a DC part. With some loads a DC component can happen. A relatively common example are hair dryers on the lower power setting that use a diode to reduce the power to half. AFAIK for hand held use this is allowed in many regions.I would not expect the CT to saturate under some 100mA, as few materials get saturation under 1 A/m and 10 cm magentic path is still relative small. So it would be hard to make the CT saturate so early. Chances are they would prepare for some DC and intentionally use a material with current needed for saturation / leaving the good range.

author: uer166
author_rank: Super Contributor
timestamp: January 12, 2022, 06:31:55 pm
content: Quote from: Kleinstein on January 12, 2022, 05:04:18 pmNone/few of the US meters are designed to tolerate DC, and in my experience you need very little current to saturate, single amps range. For MID metering in europe, they require to be tolerant to a half-wave rectified load of full current rating, and therefore you need to design CTs in weird ways. E.g. you usually have a dual (or even sometimes triple) core CT, where one material is high-permeability for high accuracy for normal loads, and a lower permeability to keep it working in case of 30A DC or whatever, but at slightly degraded accuracy.Re: even harmonics: for a DC-tolerant CT, I think you're right, they can't measure DC but may be able to measure even harmonics. In general all these edge cases can corrupt, and break:RMS measurements of V and IPower factor measurementsReactive power calculationFrequency measurement (e.g. when it's done based on zero-crossesDoes that imply that the active power becomes inaccurate?No, it does not!OP, I think you're really confused about how conducted EMI works, and how high-frequency stuff can affect metering. All that 10kHz or 100kHz or whatever, gets attenuated to nothing in the input filters, it simply doesn't meter it.

author: coppice
author_rank: Super Contributor
timestamp: December 02, 2022, 02:44:41 am
content: Quote from: uer166 on January 07, 2022, 09:03:08 amThere are some major manufacturers of electrical energy meters who use hall sensors and rogowski coils, especially in Europe. CTs and resistive shunts are more common globally, but there is nothing strange or rare about a domestic tariff meter using either a hall sensor or a rogowski coil.

author: uer166
author_rank: Super Contributor
timestamp: December 02, 2022, 02:57:56 am
content: In that case I stand corrected. Do you know of specific manufacturers/part numbers? I remember doing the math concluding that a class B meter wasn't really possible to do with Hall.

author: coppice
author_rank: Super Contributor
timestamp: December 02, 2022, 05:26:56 pm
content: Quote from: uer166 on December 02, 2022, 02:57:56 amIts several years since I worked in metering. I would probably mix up who does what now. A small British company did a lot of work trying to get accurate results from Rogowski coils constructed as PCBs, while limiting their influence from external fields. Their approach has gone into some high volume meters, although the results we found when experimenting with their approach was quirky. One of the European makers used to use Hitachi hall sensors for three phase designs, which I think were only 2% accurate. Very cool designs, though. 100% of the electronics was on a single PCB, that clicked into place, with the hall sensors on it. When clicked in, the sensors were in just the right place above the high current terminals moulded into the case. That's the cleanest meter design I've seen. At least 2 people have their own ASICs, which have the hall probe and all the conditioning electronics within the ASIC. They claim extremely high accuracy. I think L&G are one of the companies that do this.

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: December 02, 2022, 05:40:05 pm
content: I tend to be skeptical of any non-rigorous measurement or discussion of power. There are a lot of pitfalls one can stumble into measuring power. Errors in measurement account for most claims of over-unity in free energy scams. I've been measuring low PF gadgets on the job for many years. We're well equipped and some high frequency measurements are still hard and prone to errors. Sometimes we admit that getting a super accurate result isn't worth the time and effort it would take and we just move on. I have a fair amount of faith in the people that design commercial power meters, as the technology is well established and the stakes are high.

author: coppice
author_rank: Super Contributor
timestamp: December 02, 2022, 05:52:49 pm
content: Quote from: Conrad Hoffman on December 02, 2022, 05:40:05 pmThe standards for domestic energy meters focus on their accuracy from power factors of unity, where maximum accuracy is expected, to 0.5, where a relaxed accuracy is expected. Generally the approvals and calibration processes for meters do not check them below +-0.5PF, which I think is weird. Having a very relaxed spec seems appropriate, but not checking if the accuracy goes completely crazy doesn't. Its the same with small currents. Between the creep current (the minimum the meter is supposed to even register as power, so its readings don't accumulate small amounts of noise) and 5% of full scale, they don't generally even do a sanity check of the accuracy.

author: Fflint
author_rank: Frequent Contributor
timestamp: February 14, 2023, 10:20:11 am
content: Op here, I haven't gotten around to measuring my power use using CTs, because my use as charged did come down significantly after my meter was replaced when I installed my PV system. Previously I fairly routinely got bills between 600 in summer to over 1000 kWh in winter per 2 month billing period. After I installed my PV system (2.3kW only, projected annual production 2500kWh) my bills in the warm period (May-September) I got bills of few bucks per 2 months. So I basically used almost exactly the same as was generated. Now during winter my last 2 bills were on the level of summer use before. This is just anecdotal evidence, but it does seem significantly lower (by a third) than before.Furthermore, the New meter gives me an hour by hour breakdown on use/generation and as far as I can tell it is accurate. I might actually make a refund claim based on that so the energy company sends the old meter for testing. (I hope they still have it).This is just anecdotal "evidence". Anyone can say "maybe you're using less now that you have direct visibility of use", but I sure haven't made any extra effort to do that.

author: Circlotron
author_rank: Super Contributor
timestamp: February 14, 2023, 10:46:50 am
content: Quote from: uer166 on January 07, 2022, 09:03:08 amOften wondered how accurate are old timey rotating disc watt-hour meters with a half wave rectified load.

author: Zero999
author_rank: Super Contributor
timestamp: February 14, 2023, 11:00:13 am
content: Quote from: Simon on January 07, 2022, 12:47:55 pmThat's not a problem, because smoke detectors are capacitve loads, which will be more than compensated for by the huge number of inductive loads, especially in industry, where motors are the main load.

author: coppice
author_rank: Super Contributor
timestamp: February 14, 2023, 03:10:55 pm
content: Quote from: Circlotron on February 14, 2023, 10:46:50 amWhy would half wave loads give trouble with CT based meters? They are all specified to use CTs with a pretty high DC tolerance. That spec usually comes from the meter's customer (the utility) rather than a standards body. Its there, none the less.Most of the old disc (Ferraris wheel) meters work well with highly asymmetric load waveforms, unless the load is extremely high. Like the CT based meters, the core in most Ferraris wheel meters is specified to have considerable DC tolerance. I've seen some very lightweight meters, which are a bit suspect in this area, but most are OK.

author: uer166
author_rank: Super Contributor
timestamp: February 14, 2023, 05:03:31 pm
content: Quote from: coppice on February 14, 2023, 03:10:55 pmThat is not true of any US meters I've tested, and multiple MID EU certified meters thatshouldhave DC tolerance, but don't.

author: AheadOfTheTimes
author_rank: Contributor
timestamp: August 14, 2024, 11:42:22 pm
content: I know there was some question in this thread as to whether the overbilling reported was real. Now a systematic study has been done by Euramet, which is the umbrella group for the national metrology institutes in Europe; more than half the models tested showed the problem, and the overbilling was as much as 20-fold on a water pump that was tested. It does seem to only happen with Rogowski coil sensors, that may be sensitive to the very high slew rates of pulse type loads. It looks like quite a mess for consumers who have these meters. The the full report, and references to supporting reports, here:https://www.euramet.org/research-innovation/search-research-projects/details/?tx_eurametctcp_project=1543

author: thm_w
author_rank: Super Contributor
timestamp: August 15, 2024, 12:12:48 am
content: Quote from: AheadOfTheTimes on August 14, 2024, 11:42:22 pmHere is the water pump link you are talking about, its from 2019:https://www.icrepq.com/icrepq19/205-19-have.pdf4 of the 10 meters tested showed significantly incorrect readings."The power consumption related to these levels is between 23 and 130 Watt, respectively, specified by the manufacturer."Worst case deviation was 2500% at 23W level. So would read 575W instead of 23W.

author: AheadOfTheTimes
author_rank: Contributor
timestamp: August 15, 2024, 12:17:26 am
content: PS: in terms of the original question, the old Isobar filters pretty good, with toroidal chokes, multiple stages. I don't think modern ones are like that. A brute force approach would be to plug in large capacitor filters such as sold by Greenwave or Stetzer (or have an electrician wire in a filter). The capacitor-only types are of course bad in terms of PF, and they draw reactive current all the time. You'd need to have two, one on each phase (talking about US power here).

author: Siwastaja
author_rank: Super Contributor
timestamp: August 15, 2024, 08:27:07 am
content: A pretty interesting case because this is exactly why we have EMI/EMC requirements and qualifications. Either the meter or the pump is clearly non-compliant and put illegally on the market, would be interesting to know which (or possibly both).

author: tszaboo
author_rank: Super Contributor
timestamp: August 15, 2024, 09:43:14 am
content: Quote from: AheadOfTheTimes on August 14, 2024, 11:42:22 pmWell, I have a suggestion then.At home batteries that you install, with custom inverter/charger.Charge up the batteries with nice since wave, low harmonic content.Discharge the battery and feed back to the grid with large harmonic content.Free money.Hopefully it forces them to change the electricity meters that are not guess-o-meters.

author: Kleinstein
author_rank: Super Contributor
timestamp: August 15, 2024, 12:17:09 pm
content: Quote from: Siwastaja on August 15, 2024, 08:27:07 amThe article shows some waveforms for the pump. These look really bad with high current pulses of one sign and what looks like some DC component.The requirements for the power factor and harmonics may differ by region, but I would not consider this an acceptable current waveform for a consumer that is powered on for an extended time.The setup shown has the meters in series and they thus measure not just the pump, but also the consumption of the other meters down the chain. With the odd current waveform with rel. high RMS current, but low power the losses in the meter can be higher than normal.

author: coppice
author_rank: Super Contributor
timestamp: August 15, 2024, 04:43:43 pm
content: Quote from: Kleinstein on August 15, 2024, 12:17:09 pmIf those current waveforms are accurate that is a very peculiar pump. I wouldn't expect even a reciprocating pump to give results like that. I wonder what the model is? The range seems fairly limited. There are 10 rate steps, but they only cover a range of 8000 l/h to 15000 l/h - less than a 2:1 ratio. That's quite a high flow rate, though. Several litres per second sounds like it must be for a large commercial aquarium.

author: Siwastaja
author_rank: Super Contributor
timestamp: August 15, 2024, 04:47:57 pm
content: The pump waveforms are indeed absurd, looks like it's half-wave rectified, then pulsed. Even without knowing exact legal requirements, I'm quite confident it would be illegal almost anywhere. You can get by with strange loads, but only with very modest power levels. Tiny unidirectional (resulting in DC bias) short pulses approaching typical fuse ratings (thousands of VA); like those old "coffee maker half power switch using a diode" but in steroids; at least the half-wave rectification follows the sinusoidal shape.

author: thm_w
author_rank: Super Contributor
timestamp: August 15, 2024, 10:14:45 pm
content: Quote from: Kleinstein on August 15, 2024, 12:17:09 pmFrom the paper: "the energy meter reading of the static meters is corrected with the consumed energy of the following static meters"Quote from: coppice on August 15, 2024, 04:43:43 pmIts some kind of fish pond pump, but I can't find the exact model. Similar to this style:https://www.alibaba.com/product-detail/BOYU-SPM-3500D-5500D-8000D-Aquarium_1600878847903.html?spm=a2700.7724857.0.0.127e1fddENkcCDIt seems more efficient than these ones, if it meets the rating.

author: Kleinstein
author_rank: Super Contributor
timestamp: August 16, 2024, 07:07:46 am
content: Quote from: thm_w on August 15, 2024, 10:14:45 pmThere are 2 parts to the consumption, one is the supply current that is normally relatively constant and easy to correct. The other is the voltage drop at the shunt / current transformer and wiring. This part depends on the load current and with a current transformer can get even higher with the odd waveform. The distorted mains waveform from the nasty load can also effect the consumpton, up to the point that a MOV triggers from voltage spikes created by the current spikes. This current dependent loss is likely not corrected as it would be very difficult to do so.