Electronic energy meters’ false readings almost six times higher than actual - Page 1
Forum section: electronics / general

author: station240
author_rank: Unknown
timestamp: March 06, 2017, 11:38:19 am
content: https://www.utwente.nl/en/news/!/2017/3/313543/electronic-energy-meters-false-readings-almost-six-times-higher-than-actual-energy-consumptionQuoteQuoteYeah as I expected, doesn't cope with complex AC loads, eg triac dimmers driving LED lights. I also wonder about how well they deal with SMPS that aren't using PFC to average the input current over the entire waveform.QuoteMakes perfect sense, the hall effect sensors don't have the magnetic flux that would mask complex loads on AC waveforms.Also comments like this on reddit, raise questions on the build quality of the meters in general/r/news discussion on this story

author: coppice
author_rank: Super Contributor
timestamp: March 06, 2017, 11:52:20 am
content: It doesn't surprise me that some Rogowski coil designs would give trouble. The integrator needed to convert the di/dt signal from the coil to an actual current signal is often poorly implemented.

author: bktemp
author_rank: Super Contributor
timestamp: March 06, 2017, 12:09:11 pm
content: Measuring power over a large dynamic range isn't trivial. Current sensors being linear over such a large range and also being fault tolerant (short circuit currents in range of many kA, DC currents, etc.) aren't easy and cheap to build, so for loads with a high power factor a large error doesn'ts surprise me at all.ButQuoteReally? Who wrote thos requirements when an error of almost +500% is still ok?

author: HighVoltage
author_rank: Super Contributor
timestamp: March 06, 2017, 12:18:18 pm
content: I am not surprised eitherWe got an electronic meter installed about 6 month ago and I found that my average consumption has increased by about 14% although we did not change any behavior pattern that should amount to this increase.

author: coppice
author_rank: Super Contributor
timestamp: March 06, 2017, 12:20:34 pm
content: Quote from: bktemp on March 06, 2017, 12:09:11 pmMeasuring active power to 0.5% accuracy over a 5000:1 current range is a pretty cheap thing to do these days. Most consumer utility meters are built for 1% accuracy. CTs used to limit the dynamic range, but they have massively improved. Cheap CTs can now maintain better than 0.5% accuracy over a 10000:1 range. Shunts never presented a problem. Considerable care is needed with layout and isolation to maintain consistent results, but it doesn't need to cost very much.

author: Vtile
author_rank: Super Contributor
timestamp: March 06, 2017, 12:24:10 pm
content: They propably skip the accuracy requirements.Sad to hear, but I'm not actually suprised. Past two year what I have studied the electrical power and distribution field it feels like it is stuckt in 50s (especially what comes to consumer end), compared my older hightech related degree.

author: bktemp
author_rank: Super Contributor
timestamp: March 06, 2017, 12:31:44 pm
content: Quote from: coppice on March 06, 2017, 12:20:34 pmBut that raises the question why did they use Rogowski coils or hall sensors instead of CTs?They typically avoid shunts because of their power losses (who has to pay for them?)

author: Vtile
author_rank: Super Contributor
timestamp: March 06, 2017, 12:50:26 pm
content: Btw. Does anyone have the IEEC article and could look up if there is a list of meters involved in the study.

author: capt bullshot
author_rank: Super Contributor
timestamp: March 06, 2017, 01:04:11 pm
content: Quote from: HighVoltage on March 06, 2017, 12:18:18 pmIMO this would result from increased accuracy and linearitty of the electronic meter over the good 'ol ferraris counters. The usual ferraris counters here have quite large errors with small loads, mostly counting less. The electronic ones (here) are usually more accurate at small loads (say like your average household "standby" 10W ... 100W)

author: coppice
author_rank: Super Contributor
timestamp: March 06, 2017, 01:13:37 pm
content: Quote from: bktemp on March 06, 2017, 12:31:44 pmMost single phase meters use a shunt sensor. They typically use 200 micro-ohm shunts in 230V 60A meters, so there is less than a watt of loss in the shunt at full load. Other sensors are typically used where isolation is required. This includes 3 phase meters, meters for US split +-110V applications, and meters where the measurement electronics must not be live.Rogowski coils are cheaper than CTs, as they have no costly ferrite, so people love the idea of using them. However, they are not easy to get good results from, and globally usage of Rogowski coils for consumer meters is still limited. They are rather susceptible to external alternating magnetic fields, and accuracy can be affected by surrounding equipment. Well screened CTs are only disturbed by intentional tampering, such as attaching powerful magnets to the outside of the meter.Its hard to get good results with Hall probes from the merchant market. However, some meter makers, such as Landis and Gyr, have their own ASICs with integrated Hall sensors, which appear to achieve high accuracy. I don't know much about their pros and cons.

author: coppice
author_rank: Super Contributor
timestamp: March 06, 2017, 01:20:09 pm
content: Quote from: capt bullshot on March 06, 2017, 01:04:11 pmSome Ferraris wheel meters are cheaply made, and suffer corrosion and other degradation with age. However, most of the Ferraris wheel meters in Europe are very stable. You can take a meter from a house after several decades of use, put it on a test set, and it will still pass the accuracy tests. They give better than 2% accuracy over a fairly wide current range and power factor range, although its hard to make them more accurate than that.Both Ferraris wheel and electronic meters are designed not to read below a specified starting current, which is set out in the specifications. They typically start at something like 10W, although the start point varies from place to place. This feature is intended to eliminate any tendency to creep under no load conditions, and slowly record usage when there is no load at all.

author: HighVoltage
author_rank: Super Contributor
timestamp: March 06, 2017, 03:28:48 pm
content: Quote from: capt bullshot on March 06, 2017, 01:04:11 pmAhh,You are saying that the old ferraris counter read low instead of the electronic meter to be reading high.That could very well be.Will be interesting at year end to see a full year comparison.

author: G7PSK
author_rank: Super Contributor
timestamp: March 06, 2017, 03:57:19 pm
content: Only 50% over? some of them are out by factors of thousand, with at least one customer having apparently used £38,000 pounds worth of electricity in a single day.http://www.bbc.co.uk/news/uk-39169313I would refuse the installation of a smart meter and if it becomes compulsory I will install an old fashioned meter after said smart meter which should me labeled stupid under the trade description act.

author: Kleinstein
author_rank: Super Contributor
timestamp: March 06, 2017, 04:54:13 pm
content: The very bad readings with being off by more than 10% only appear at very low power consumption and likely this is only with critical loads. So even if there are 100% off during these time, the overall energy reading for a typical household can still be better than 1%. It is a little like with those cheap plug in energy meters: they don't work well on a 0.2 W switched mode supply in stand by, but usually still read good with a 2000 W electric heater or a 100 W incandescent lamp.The way the meters are wired in the picture, the first meter will also measure the consumption of all the other meters in the chain. Depending on the internal construction the meters own consumption can change a little with changing waveform in the grid - so it might not be accurate to just subtract the initial value. Not sure they even tried.

author: coppice
author_rank: Super Contributor
timestamp: March 06, 2017, 05:15:07 pm
content: Quote from: Kleinstein on March 06, 2017, 04:54:13 pmThe IEC specs used in most countries define a pattern of accuracy requirements, requiring a 1% meter to be better than 1% accurate between power factors of 0.8C and 0.5L, and between typically 1A and the maximum operating current of the meter. Down to typically 0.5A they are allowed a little more error. Down to typically 0.2A they are allowed a bit more. Oddly, between the start current and 0.2A there is no accuracy spec at all. However, I have never seen a meter maker happy to ship a meter which is worse than maybe 3 or 4% in error in this current range, or at power factors outside the range 0.8C to 0.5L.As you said, the meters are shown chained, which would make the meters read the consumption of those meters downstream. If the tests were conducted at low power levels, which might be true if those lamps are LED types, and no other larger loads were used, this would add significant error to their readings. However, it shouldn't create 582% errors in anything but the no load condition.

author: Frost
author_rank: Regular Contributor
timestamp: March 06, 2017, 05:41:16 pm
content: Quote from: Vtile on March 06, 2017, 12:50:26 pmAt the paper they did not tell the names of the meters.But here is a photo that shows the test setup and the meters.https://www.utwente.nl/.uc/i36/77f4d70102f10c74009800c9038a3c0b003f09d8010701c3dc05000080.jpg

author: tronde
author_rank: Frequent Contributor
timestamp: March 06, 2017, 06:37:50 pm
content: This seems to be the article.http://doc.utwente.nl/102016/

author: capt bullshot
author_rank: Super Contributor
timestamp: March 06, 2017, 07:23:31 pm
content: Quote from: tronde on March 06, 2017, 06:37:50 pmThe whole article doesn't appear trustworthy to me:- The meters are connected in series, so the first one measures not only the load but also the power consumption of the next meters and so on. It isn't mentioned in the text that this was compensated in any way.- They've used the ferraris counter as a reference, there's no comparison of the ferraris meters results to a lab grade power meter- they do not show the absolute power values, so one cannot judge if the deviation is inside the spec- Their example waveform doesn't look too difficult for a meter, if you look up the table, there's little deviation with this waveformThere's a sentence that sounds plausible to me:"Probably active integration is usedinstead of passive integration, and the input electronics arepushed in saturation caused by the high rise-time of the cur-rent."Their published waveforms and readings do not explain this, it's just a pure guess. If you look up some datasheets of power metering ICs using rogowski coils, some of them use integration in the digital domain, so I'd consider this behaviour a serious bug. Would be interesting to exercise some eval kits ...

author: Towger
author_rank: Super Contributor
timestamp: March 06, 2017, 07:27:04 pm
content: The electricity supply company here have started a program to replace a large number of digital meters, due to them over reading.-----------The affected electricity meters were installed mainly in apartment blocks around the country from 2007 onwards.27,000 customers have been written to and informed that their meters will be replaced and tested, but ESB Networks is primarily concerned with a batch of around 17,000 meters.It estimates that around 10% of these could be faulty.The fault is thought to be caused by deterioration in one of the components which causes the meter to over-record, before it stops working.This can result in some customers being incorrectly charged.ESB Networks said it will be able to determine from tests whether customers have been wrongly billed and will refund any money overcharged.The company said in a statement: "ESB Networks advises all customers that they do not have to take any action with their meters."ESB Networks will contact all affected customers and test the meters."Speaking on RTÉ's Morning Ireland, ESB Networks spokesperson Bernadine Maloney said: "The meter typically over records and then fails. It's important to note that customers won't lose their supply, the meter just stops reading and there's no safety issue at all."

author: Iwanushka
author_rank: Frequent Contributor
timestamp: March 06, 2017, 09:56:16 pm
content: some of those digital bastards can even track a 1.5V led connected via 1M resistor to mains

author: Vtile
author_rank: Super Contributor
timestamp: March 06, 2017, 10:26:13 pm
content: It could be definedly better, the paper is too vague in many aspects, but atleast it does somewhat show that with non-linear load you can getwildmeasuring error. In ten years period even 10% error gets costly if it happens in your direction as a customer, not to mention if you run a small manufacturing business (carage level on my mind) and your power consumption is measured such meter. Not good as this kind of things are harmfull for whole industry even long after the things are corrected.Not to mention those professionals who have done the decision to go with certain type of meter.

author: james_s
author_rank: Super Contributor
timestamp: March 06, 2017, 10:54:26 pm
content: Quote from: HighVoltage on March 06, 2017, 12:18:18 pmThe old meters do tend to slow down a bit with age. They are mechanical devices, bearings wear, lubrication dries up, it wouldn't surprise me in the least if your old meter was running 14% low by now.

author: tronde
author_rank: Frequent Contributor
timestamp: March 07, 2017, 01:30:24 am
content: Quote from: Vtile on March 06, 2017, 10:26:13 pmYou seems to be from Finland?Can't you ask Aidon some questions about this report?http://www.aidon.com/fi/yhteystiedot/

author: Vtile
author_rank: Super Contributor
timestamp: March 07, 2017, 09:16:11 am
content: Send them email. You have the questions.

author: amyk
author_rank: Super Contributor
timestamp: March 07, 2017, 12:15:57 pm
content: Quote from: coppice on March 06, 2017, 01:20:09 pmI wonder how many have observed this and tried to profit from this source of "free energy"

author: tszaboo
author_rank: Super Contributor
timestamp: March 07, 2017, 12:35:46 pm
content: Quote from: G7PSK on March 06, 2017, 03:57:19 pm"Yes, I have a 200KA circuit breaker at home, and I was burn-in testing the new orbital defense laser grid."

author: coppice
author_rank: Super Contributor
timestamp: March 07, 2017, 02:23:10 pm
content: Quote from: amyk on March 07, 2017, 12:15:57 pmWell, if the only appliance in the house which is on is, say, a phone charger it won't be charged. Its hard to get much value out of loads below the start current, though. You might if you could charge a storage system at a steady 7 or 8 watts, 24 hours a day.Water meters, on the other hand, do offer the ability to get useful amounts of free water. Most water meters are mechanical, and the mechanics have some stickiness. Most water is used in small bursts. Spread out your consumption over 24 hours, and you might stay below the point where the meter unsticks and records. Put the plug in the bath tub, and leave the tap dripping all day. Now you have many litres for free. This is a problem in some parts of the world, where families can obtain most of the water they need without it being recorded.

author: james_s
author_rank: Super Contributor
timestamp: March 07, 2017, 04:42:09 pm
content: I've had a smart meter for years, it's a conventional electromechanical meter with an additional portion that enables remote reading. It's great because I can log into my account and see the day to day consumption. I never really understood the resistance to these things, they're a convenience for both the utility and the customer. An additional perk is that meter readers don't have to come onto my property regularly to read the meter.