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I am looking into Power Line communication (PLC) as a means for smart metering. It looks totally possible to send the data from the meter to the source of the power supply or the transformer.

Most of the smart meters use Wifi. Are there any technical/practical challenges to implement a PLC based smart metering network? Thanks.

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  • \$\begingroup\$ Welcome to EE.SE! Try to avoid asking for product recommendations (asking for a development board recommendation). Product recommendations like this ride the line a bit on this site. \$\endgroup\$
    – Daniel
    Dec 20 '17 at 8:16
  • \$\begingroup\$ @DanielGiesbrecht Sorry. I edited the question. Thanks. \$\endgroup\$ Dec 20 '17 at 8:20
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As someone who worked on PLC at university:

Yes, PLC is being used for grid control and metering applications.

So, there's already a lot of meters that implement that. There's standards (e.g. EN 50065); you don't seem to have come very far in your research!

Are there any technical/practical challenges to implement a PLC based smart metering network?

Yes. Plenty. Like, really many. Compared to your usual wireless channel, or your usual dedicated communication line channel; even compared to your DSL channel.

For example: Power lines have extremely low sink impedance. That's not cool if you need to generate a signal of significant amplitude.

Then: Power lines have high attenuation. In fact, the higher you go (and I'm talking about a couple 100 kHz), the uglier it gets. But, hope not: Noise is exactly strongest where attenuation is lowest¹. So, worst case for a frequency-selective communication channel.

Then: Many channels are considered stationary; PLC is not. It's very very strongly cyclostationary, with periods where it's nearly unusable. Great!

Oh, and also: where wireless communications engineers often either consider white noise, or narrowband interferers, the usual PLC channel model has several narrowband interferers (often with cyclostationary behaviour themselves), and plenty periodic and aperiodic impulse noise. Impulses are broadband.

Then there's the whole business of not being allowed to interfere with the devices attached to the grid.

Also, but I don't know if this is actually backed by facts, but it does sound likely: PLC, when used in far-reach communications over high-voltage lines, is being blamed by amateur radio enthusiasts for heavy interference. Just another thing that you need to worry about.

That all being said: PLC is dead for indoor internet, exactly for the reasons Bimpelrekkie cites. WiFi is faster (much more bandwidth, even with all the ISM band interference!), also doesn't reach all rooms in a complex building, but is more easily extended, uses less power and most importantly is way way cheaper. PLC seems relatively alive in the grid sector, where having an extra comms line can be expensive. Different countries and suppliers use PLC as their standard for meters, and for smart grid applications. There's been recent efforts to emulate channels² for the sake of being able to actually fully test bidirectional modems with reproducible scenarios (something inherently hard to do, compared to wireless channel measurements).

Generally, the PLC backhaul channel is an interesting beast, and applying what we wireless communications engineers do with software defined radio and cognitive radio approaches sounds wise; if you're into that, look for the dissertations of Kaiser and Otterbach (as soon as they're published).


¹ Han, Kaiser, Otterbach, Stoica: "Noise Characterization and Emulation for Low-Voltage Power Line Channels between 150 kHz and 10 MHz", available online ² Han: https://www.ksp.kit.edu/9783731506546

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  • \$\begingroup\$ Brilliant answer, can you elaborate a bit on what the sink impedance issue is fundamentally about? If I guessed correctly, this can become a problem any time a signal is piggybacking over something else... \$\endgroup\$
    – Milind R
    Oct 12 '21 at 11:56
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    \$\begingroup\$ Imagine this: you connect a 1.5 V battery to a 100 kΩ resistance, and measure the voltage over that resistance. It's going to be 1.5 V, pretty much. You now take that same battery, and connect it to a 100 µΩ = 10⁻⁴ Ω resistance. That's basically a short. The voltage over that will pretty much be 0 V, and your battery will get very hot. The same with power line: the power plant defines the voltage on it. If I connect a battery to an outlet, I don't get 1.5V across that outlet, I get 230 V and an exploding battery! Being a low-ohmic sink makes it very difficult. \$\endgroup\$ Oct 12 '21 at 12:50
  • \$\begingroup\$ Hmm, maybe put a 230V/5V transformer across the mains, and impose 5*sin(100 \$\pi\$ t) in sync with the mains, plus 0.1*sin(\$\omega\$ t) with frequency in the Mhz range on it? I assume the high frequency would make the grid have a much higher impedance hopefully?...... I think I understand the complications involved which weren't apparent when I was thinking conceptually rather than about how to actually do it as an electrical engineer. Thanks! \$\endgroup\$
    – Milind R
    Oct 15 '21 at 19:58
  • \$\begingroup\$ So the driver would have to have a high input impedance itself so that it makes sure not to source too much current... \$\endgroup\$
    – Milind R
    Oct 15 '21 at 20:02
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    \$\begingroup\$ no, your problem is that you must have a driver with low impedance, because you need to change the voltage on the line: "saving power" isn't the purpose of the driver, it's "putting information on the channel". \$\endgroup\$ Oct 17 '21 at 18:51
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Yes, what you suggest is possible and you can buy adapters for using the mains wires as ethernet, see: Power-line communication.

But that puts the data on the mains lines so you would still need a 2nd Power-line adapter to connect to your internet connection, either via cable or WiFi.

So that 2nd adapter would add cost. Since most people have WiFi already it is often cheaper to directly use WiFi.

Maybe you are suggesting that the communication from the smart meter to the utility company takes place over the mains wires? Unfortunately that will not work, Power Line communication can work on the last miles but not all the way back to the utility company. Not without major changes anyway.

Even if a new system would be used designed for a longer range that range would still be limited and costly changes to the mains system might be needed. Note that there are many transformers present between the power station and your home, these transformers will easily attenuate or even block any signals you're trying to get through.

All in all, using WiFi is much cheaper and convenient as most of the infrastructure is already in place.

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  • \$\begingroup\$ Sorry, having worked on PLC: PLC can be used for last miles, not only locally; there's transformer bridging technologies. \$\endgroup\$ Dec 20 '17 at 8:53
  • \$\begingroup\$ OK, updated with that info. \$\endgroup\$ Dec 20 '17 at 8:57
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As someone who has deployed hundreds of thousands of smart meter devices my God do I hate PLC. Always so much promise, always such little delivery in the field. On the surface it seems like it should be so much more reliable. After all a cable connection doesn't have that wireless interference problem. But oh, then you get in the field and this country has super low impedances everywhere swamping out your signal. Or oh yeah that leg of 500 units isn't connected to the same leg where your take out point is so obviously that'll never connect. You better hope your front end is robust enough to handle surges, disconnect event spikes, lightening etc. Those power lines are way noisier than you'd think out in the field. Nothing like the lab.

There are several standards as people say IEEE 1901.2, PRIME, G3-PLC, CTIA/EIA709.2, and lots of proprietary ones. There are companies that specialize in making PLC modems like Semitech. I've spent more time than I like to think about tweaking PLC designs, making tools to examine the spectrum on the line, finding the right channels. Then the testing, the field installations and...

I'd take a wireless mesh solution any day over PLC. Lora, WiFI mesh, even Zigbee and the like. All those solutions have been deployed much easier than any PLC system I've seen. But maybe you'll have better luck ;) I'd personally only do PLC on short runs like LED lighting controllers or in a very controlled environment. There are definitely large PLC deployments out there but given the choice I'd rather have wireless. That comes with its own challenges but in my experience in the field has been the most robust solution.

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