In the era of mechanical electric meters, there is an urban legend that there are "lucky" electrical appliances. Once plugged in, the electric meter will go backwards. It may originate from the interaction between the strong capacitive load and the inductance of the coil in the meter, but for ordinary home users, this is still largely fabricated. This is not to say that meters cannot be fooled to do strange things, as a team at the University of Twente proved by sending some more modern meters to run backwards. How did they create this miracle? Electromagnetic interference from the dimmer switch.

Reading the paper (PDF link), it is obvious that this behavior is the result of the dimmer switch being able to shift the phase of the current pulse relative to the voltage cycle. AC dimmers are obsolete in 2021, but for those unfamiliar with their operation, they work by turning on themselves only during a part of the main power cycle. The cycle time is changed by dimming control. Therefore, the time between the zero-crossing point of the mains and its conduction point is equivalent to the phase shift of the current waveform. Since electric meters rely heavily on this phase relationship, their performance can be adjusted. Perhaps European stores will now be ready for the use of dimmer switches.

If you are curious about these old-fashioned dimmers, please check out some of their basic functions.

Thanks [Dorus] for the tip.

I want to know what the small board attached to the surface of the meter is doing?

Count the number of LED flashes of the meter and send the reading to the computer

The paper did not explain much about the nature of the electromagnetic field that affects the power meter. The "researcher" did not measure conducted and radiated emissions in accordance with the methods in the EMC standards applicable to the equipment.

I am not aware that any certified "static" power meter currently manufactured does not have reverse current detection. I have seen some cheap (and inaccurate) things in China that can be tightened, but other than that, the power meter I tested knows when there is a problem at the consumer site.

The non-linear power consumption of electrical appliances is a new thing in the paper. For most of this century, most things must meet standards such as IEC61000-3-2, which means that the power supply will use PFC, which means that these types of current waveforms should not be seen, which means they are testing Non-eligible equipment.

To be fair, IEC61000-3-2 does not outline any requirements for PFC in power supplies.

All the outlines in the IEC61000-3-2 standard are the power harmonic noise of electrical appliances, and the level that is not allowed to be exceeded. In many cases, some power filtering is sufficient to allow the device to pass. Nevertheless, there are some types of electrical appliances that do not comply with the IEC61000-3-2 standard.

So you jumped too far: "This means you shouldn't see these types of current waveforms, which means they are testing substandard equipment."

However, I am not saying that the test only used equipment that meets the requirements, but that there are exceptions to the IEC61000-3-2 standard, and it only covers the low-frequency part of EMI. (Up to the 40th harmonic, for a 60Hz power supply, there is only 2.4 kHz. To be fair, this is a fairly low frequency. Considering an example, how most SMPS units work at more than 10 times this frequency. But this is obviously A completely different category of noise covered by other standards and regulations.)

Then there is the statement about power factor correction, which is actually not common for most appliances. In a typical household, there may be only a few appliances with active PFC. The most typical is a desktop computer equipped with a "premium" power supply. Even power-consuming devices like induction stove tops do not have PFC. They usually just use the main sine wave, which is the same for many LED lights (flickering as a side effect). Not to mention mobile phone chargers and other "small" power supplies and appliances, which have almost no PFC function at all. Some IoT products only use capacitive dropper, and the power factor is usually lower than 0.2

But also, the induction furnace top connected to the main power supply can generate the smallest harmonics, and can "easily" filter out its switching noise. For some of the capacitive bucker power supply of some IoT devices, the current through its bridge rectifier can also be filtered out (or quite a lot of series resistance can be added to work a bit "decently"), this also applies to switch mode and linearity power supply.

But dimmers based on triacs may be more difficult to filter out its problems. These dimmers have been common for decades, so I wouldn't be surprised if they have some exceptions. For better or worse.

We can reduce the W power by reversing the PFC and power factor reducer circuits. Free Energy.

I don't think PFC is needed for power below 100 watts. Of course, the power supply of my grandparents 32-inch LG LED LCD does not have PFC. I had to take both apart, the old one had damaged the backlight LED, and the new one burned a high-voltage capacitor on the primary side out of warranty.

The article pointed out that all power meters comply with IEC. The load contains a universal dimmer, which usually does not have a PFC.

The problem is not that there is no reverse current detection, but that current peaks with a specific phase angle can cause erroneous measurements. By the way, these two methods are effective, and researchers can also make the meter display excessive usage.

The conclusion is that a meter that complies with the relevant IEC standard cannot guarantee correct measurement.

At least one of the meter model manufacturers shown does not comply with the EMC Directive. The other has D of C, but does not refer to any harmonized standards in EMC or LVD directives. Some may be, but I cannot identify all imaging devices.

Does anyone else have any regulatory information about these things?

Now I want to know if there is something in my house that makes it look faster!

This kind of equipment has a broad term: load.

Loading doesn't make it "seems to run faster", but it actually makes it run faster. He was talking about things that might make the load look bigger than it actually is.

There is quite a lot of weak science in the paper—the case where the meter records negative consumption corresponds to the case where the THD of the power supply is far more than 5%—not surprising given that they are talking about crest factors between 48 and 42. They also did not consider the difference between live power and AC power output-especially in terms of transient behavior and line impedance, which will have a significant impact on higher harmonics.

It also does not consider the difference in behavior between traditional electric meters and modern smart meters, which are designed to measure in four quadrants-in this case, highly non-linear loads may appear to be fed back to the power supply Medium-I noticed that they have failed to calculate the effective impedance of the load. The dominant negative impedance seems to be powering the network.

Another thing not considered is the EMC compliance of the switch dimmer in question and the impact of the non-compliant unit when its load accounts for a large proportion of the load-especially considering that it generates 50A on each load. Peak half cycle.

The scary thing is that although in some cases the meter displays far lower than the actual consumption (or power generation instead of consumption), it displays much higher than the actual consumption under other conditions.

In the United States, old-style meters can be inserted in the reverse direction to reduce usage. I have a sister-in-law who did this, and she got "credit" on her next bill. Needless to say, my brother raised hell and then switched it back. New rice, not so much...

I still have a vortex disc flow meter, it will not go backwards because it has a ratchet to stop this type of pranks. However, this caused me a problem, because my solar (grid-connected) power generation experiments often produced more electricity than I could use, and the excess would enter the grid, so the power generation company got it for free.

I want to know if the electricity meters in the Netherlands can be specifically reversed to encourage people to install solar energy, so on a good day, they power their neighbors and reduce bills. Do we have Dutch readers who can comment?

The old analog meter will indeed be regressed due to the excess solar energy, and the new meter we can only get 5c from the sale of electricity (we buy it at 25c). Batteries are now a better solution.

You should switch to e-commerce. Now according to the law, they must refund your electricity supply tax in full until you have invested more than one year of net income. So unless you earn a lot more than you use, you can use the grid as an unlimited free battery.

New "smart" meters usually have 4 or 6 independent counters for 2 different rates, supply and usage. The old meter actually turns backwards and can be locked by strategically placed magnets.

Opinion polls for several years have been repealing laws that require supply to be compensated at least at the same price as the use (called "salderen") because of the duck graph and calls for more difficult load balancing, and even some songs with unsafe conditions. The sub-grid is powered when it should be shut down. It's all nonsense, the one who has cried is not doing load balancing. Load balancing is a problem in itself, but this is mainly because politicians prefer to cater and posture, rather than spend money where needed. As far as I know, this is a problem everywhere.

Can't say that I have seen a mechanical electric meter. How do these work? All the old styles I have seen use vortex.

They have rotating discs with black stripes. You know, mechanical parts that are matched with electrical parts, not specialized electrical parts.

A few years ago, when I majored in physics in college, I joined the drama department for fun (and better dating prospects). I made a four-channel light dimmer based on SCR for some of our productions in the student union. It was accidentally discovered that certain dimmer settings would cause the class schedule bell to ring throughout the campus (the central timekeeper sent audio commands to the bell through the power cord). It's interesting to see people suddenly stop playing bridge and rush into the class only to find that they come too early. In the next three years, people who installed the bell system showed up many times in an attempt to eliminate this unstable operation. Obviously no one noticed that I never sounded again after graduation...

I heard somewhere that those electronic power meters sometimes make mistakes, and PWM dimming LEDs (only measuring peak values). As for the instruments of the old age, a friend of mine has a very low usage rate for many years: they used to put a photo film between the glass and the instrument frame, the witch can stop the wheel, of course they have to run it for a few days a month , So they can have bills...

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