Smart electricity meter installation

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timmmay

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#1735715 13-Mar-2017 13:16

Aredwood:

I have since found out that my meter is consistently reading a power factor of more than 0.9 Which if true will explain my power bills.

Could you explain this a touch more? My "smart" meter gives me a bunch of information, if I push the right buttons, from memory power factor might be something it can tell me.

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robertsona

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#1735719 13-Mar-2017 13:23

JayADee:

Electricity company wants to put one on our house. Any cons to it? Thanks.

Cannot believe no-one has yet dredged up this old one: http://www.stopsmartmeters.org.nz/

neb

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#1735722 13-Mar-2017 13:31

robertsona:
JayADee:

Electricity company wants to put one on our house. Any cons to it? Thanks.

Cannot believe no-one has yet dredged up this old one: http://www.stopsmartmeters.org.nz/

I took parts of the smart-meter symptoms stuff I had in my post from anti-smart-meter web sites, probably including that one. You can try and figure out which parts of my post are satire and which are from actual web sites.

tripper1000

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#1735801 13-Mar-2017 14:53

I can believe that smart meters that were once adequate and accurate could now be inaccurate and inadequate.

New technology can play havoc with existing standards and existing equipment. Without researching the standard for your self, some CEO indirectly answering accuracy questions by saying their gear is built to a NZ Standard (or similar) is a legal defence, not a technical reassurance.

I have seen examples of masses of switch-mode power supplies creating huge 3rd harmonics and causing heat generation in the neutral wires of 3 phase power systems in large office buildings. The wiring was up to standard, but the technology plugged in had changed and the situation was never anticipated by the standard.

JayADee

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#1735982 13-Mar-2017 20:12

I'm beginning to wish I'd stuck with my dumb one.

kiwifidget

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#1735996 13-Mar-2017 20:47

This in the Herald. How do you find out what sort of smart meter you have?

http://www.nzherald.co.nz/business/news/article.cfm?c_id=3&objectid=11816828

Delete cookies?! Are you insane?!

JayADee

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#1736012 13-Mar-2017 21:11

I've emailed the power co I am with and also the supplier of the unit, Wells. I haven't heard back from either one.

richms

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#1736060 13-Mar-2017 21:21

current transfromers are hopeless if there is a DC component to the current waveform - like a hairdryer on low where they just chuck a diode in series with the heating elements.

Richard rich.ms

JayADee

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#1736861 15-Mar-2017 13:45

Got my reply back.

Hi,

Thank you for your email.

I have received a reply from our Metering Team as below.

The meter at your property is a Metrix Smart Meter, the following was stated in the article by Metrix: (graphic of article deleted)

The meters that were tested overseas were Rogowski Coil Meters which is not used at all by Metrix.
Majority of their meters are Current Transformers (CT) or Shunt Resistor Sensors meters.

I hope this is helpful to answer your query.

Aredwood

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#1740575 17-Mar-2017 00:09

sir1963:

JayADee: Gah! A week after my meter is installed I read this: http://www.nzherald.co.nz/business/news/article.cfm?c_id=3&objectid=11816828

which says a lot of them are very inaccurate!

I've emailed my provider to find out what kind I've got.

Heres another article

https://hardware.slashdot.org/story/17/03/12/2256215/millions-of-smart-meters-may-over-inflate-readings-by-up-to-600

That article states - " Researchers also used one electromechanical meter for reference... " If they were assuming that the electromechanical meter was 100% accurate, and were using it as their standard. Then they can't really claim much. As how do they know if the differences in their readings were due to meter X over reading, or meter Y under reading? Sure their research is a good starting point. But they need to start analysing what kind of current waveforms cause the over reading or under reading. Spinning disc meters will compensate for leading or lagging current waveforms - but these waveforms are still sine waves. I certainly wouldn't trust a spinning disc meter to accurately measure any non sine wave current waveform.

And to make it even more complex, some energy saving lights use the valley fill circuit, or a variant of it. Problem is that circuit produces some very interesting looking current waveforms. Which would be a nightmare to measure accurately. And made even worse in real life there is resistance in the wiring between the street transformer and the electricity meter. Meaning any kind of non sine wave current waveform will also produce voltage ripple. Yet another thing the electricity meter needs to compensate for.

And these weird current waveforms will also cause nightmares for electricians when arc fault circuit breakers become common. As the weird current waveforms and voltage ripple will cause them to trip, even when there are no problems with the wiring.

timmmay:

Aredwood:

I have since found out that my meter is consistently reading a power factor of more than 0.9 Which if true will explain my power bills.

Could you explain this a touch more? My "smart" meter gives me a bunch of information, if I push the right buttons, from memory power factor might be something it can tell me.

You probably would be able to get the meter to tell you what your real time power factor is. Heating elements and filament lights (resistive loads) have a power factor of 1. So for most houses a power factor higher than 0.9 would be perfectly normal. But for me I don't know if my 0.9 power factor as reported by the meter is actually correct or not. As I don't have access to a high end digital oscilloscope that can accurately calculate things like that.

Next part of this project is to get a hall effect current clamp. So I can at least view the current waveforms on the mains cable to my house using my analogue oscilloscope.

neb

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#1742754 17-Mar-2017 13:55

Aredwood:
That article states - " Researchers also used one electromechanical meter for reference... " If they were assuming that the electromechanical meter was 100% accurate, and were using it as their standard. Then they can't really claim much. As how do they know if the differences in their readings were due to meter X over reading, or meter Y under reading? Sure their research is a good starting point. But they need to start analysing what kind of current waveforms cause the over reading or under reading. Spinning disc meters will compensate for leading or lagging current waveforms - but these waveforms are still sine waves. I certainly wouldn't trust a spinning disc meter to accurately measure any non sine wave current waveform.

They weren't using the electromechanical (Ferrari) meter as a definitive reference, that came from the equipment they were using to generate the power, a Spitzenberger and Spies four-quadrant amplifier. What they were investigating was complaints that "smart" meters overread compared to a traditional Ferrari meter, so they measured the readings relative to the Ferrari.

The smart meters actually did pretty well in most cases, it was only when dimmers were thrown into the mix that they went all over the place, e.g. one meter reported a mains frequency of 107Hz because it used zero-crossing detection and the noise on the line caused multiple zero crossings.

They did some very detailed analysis not only of the power waveforms but also of the meters to try and figure out how they were getting the incorrect readings. Problem is the meters are complete black boxes, there's zero information available on how they do active power reading, how they process the data, or what technology they're using. So you've got ADCs coupled to DSPs that do who-knows-what, for example to sample a 50Hz signal a second- order sigma-delta ADC sampling at 500-600Hz should be fine, except that a switchmode power supply under light load would consume a lot of power at high frequencies so a low-sample-rate ADC would misread.

tl;dr: Resistive loads, CFLs, LEDs, etc are fine, it's adding dimmers that causes the problems. From a consumer point of view, a Hall effect sensor is best because it consistently under-reads, Rogowski coils are the worst by a large margin, and current transformers (CTs) are the best in terms of accuracy, but also the most expensive.

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