PLC (power line communication)

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Get in touch with Siemens in Germany, they have developed PLC systems. Since you wanted issues, here's a couple of non-technical ones:

- Power lines were not designed to carry high frequencies, any attempt is a hack.

- Tests have made it clear that the radio spectrum is badly poluted by PLC

- As power lines act like antenna's, secure data transmission is virtually impossible.

- Ham radio operators will climb the barricades and raid your offices

- PLC is an 'invention' from power companies wanting to get double profit from their network, regardless of consequences

Data over power lines is as silly as 230V over phone lines. It's a hazard in more ways that you can imagine and a bad idea.

Rob

Rob Turk wrote: ...

Good luck, but it is a good tip as they are the leaders in the field.

I think we figured that out!-)

Not in the last four years as power spectrum progress has been made. For in-your-house use they are trying techniques similar to that used by cell phones to find "usable" frequency and power levels.

You can say that again. But then signal-to-noise ratio has always been a challenge.

It's amazing that anything will work for even a little while!

What barricades???

But they would have to revamp their infrastructure to add high freq coupling, et cetera.

Surely you meant to say 230VAC? Yes, the hazards are very real and will probably prevent cost effective solutions in the near future. - RM

The main problem is (besides the obvious interference problems) the line attenuation: a standard power cable insulation has an attenuation of up to 80 dB/100 m of cable. To get the planned 500 m coverage, the circuit attenuation is in the order of 400 dB, i.e. three times as much as the attenuation of an Earth-Moon-Earth radio link.

Most of the RF problems come from the fact that the power wiring has the signal and return wires taking wildly different routes, so the whole wiring acts like the antennas of Marconi and Popov a century ago. How could the poor signal know that this time it's not supposed to radiate?

(The competitor, telephone cabling is very different in this respect).

Measurements from the PLC tests show noise levels exceeding the agreed limits by 60 to 70 dB, a power ratio of a million or more.

This is the smallest problem which can be alleviated with suitable encryption.

Try PLC and you'll see them around you. (Could not resist ...)

AFAIK, British authorities have prohibited PLC trials nearer than 100 km to their receiving radio stations.

Ham radio is not the only legally operating HF service affected by PLC: there are the maritime and aeronautical telecommunications and certain government-operated services, too.

PLC is intended to run over the 230 VAC (or whatever you get from the wall socket) lines. With current IC technologies, there is no inexpensive way to integrate it.

The main competitor is *DSL from the phone companies, which is integrable, so there is a definite advantage to DSL side.

---------

Before someone notices it:

I have an interest in this discussion, I work as technical specialist for the local air safety authorities, and I have a ham licence (oh2ug) since well over 40 years.

Tauno Voipio tauno voipio @ iki fi

There are different approaches. Some work well while some others won't. The most recent attempts with wideband is indeed a bad idea. However, coupling signal with lower expectations does indeed work. Eg we have very good experiences with 55kHz FSK doing 1200 Baud over powerlines. The other experiences with 140 to 400kHz were less good. Apparently the higher the used frequencies, the more the geometry of the "not controlled" line layout came into play in form of self-interferences.

What reach and what baudrate were you loocking at ?

Rene

--
Ing.Buero R.Tschaggelar - http://www.ibrtses.com
& commercial newsgroups - http://www.talkto.net

Hello, Rene! You wrote on Sat, 19 Jun 2004 14:34:02 +0200:

RT> There are different approaches. Some work well while some others won't. RT> The most recent attempts with wideband is indeed a bad idea. RT> However, coupling signal with lower expectations does indeed work. RT> Eg we have very good experiences with 55kHz FSK doing 1200 Baud over RT> powerlines. The other experiences with 140 to 400kHz were less good. RT> Apparently the higher the used frequencies, the more the geometry of RT> the "not controlled" line layout came into play in form of RT> self-interferences.

RT> What reach and what baudrate were you loocking at ? Actually, now I'm researching the opportunity of using PLC in home automation. So, we are designing set-top-box and would like to include the feature of PLC for controlling other home consumer electronics. RT> Rene

With best regards, Roman Mashak. E-mail: snipped-for-privacy@tusur.ru

Hello, Rob! You wrote on Fri, 18 Jun 2004 11:26:54 +0200:

RT> Get in touch with Siemens in Germany, they have developed PLC systems. I suppose this standard is not open and Siemens will ask money for consultation ;) RT> Since you wanted issues, here's a couple of non-technical ones: RT> - Power lines were not designed to carry high frequencies, any attempt RT> is a hack.

With best regards, Roman Mashak. E-mail: snipped-for-privacy@tusur.ru

Hello, Tauno! You wrote on Sat, 19 Jun 2004 07:44:53 GMT:

TV> The main problem is (besides the obvious interference problems) the TV> line attenuation: a standard power cable insulation has an attenuation TV> of up to 80 dB/100 m of cable. To get the planned 500 m coverage, the TV> circuit attenuation is in the order of 400 dB, i.e. three times as TV> much as the attenuation of an Earth-Moon-Earth radio link. I think it could be critical for home grid.... TV> Most of the RF problems come from the fact that the power wiring has

[skip]

TV> PLC is intended to run over the 230 VAC (or whatever you get from TV> the wall socket) lines. With current IC technologies, there is no TV> inexpensive way to integrate it. In my previous reply I mentioned we are going to use PLC in home automation project. What can you say about using PLC in home grid infrastructure ? TV> The main competitor is *DSL from the phone companies, which is TV> integrable, so there is a definite advantage to DSL side.

With best regards, Roman Mashak. E-mail: snipped-for-privacy@tusur.ru

Take a look at

I believe these use schemes similar to ADSL to get 10+MBaud speeds, and they are designed to operate under a standard.

-jg

See:

================================

Greg Neff VP Engineering

*Microsym* Computers Inc. snipped-for-privacy@guesswhichwordgoeshere.com

With a suitably slow data rate, the home wiring will be OK, but do not expect to transfer megabits at any distance with the power wiring - any signal transfer will be outside the wiring, as a radio network.

For most home control applications, a couple of tens or hundreds of bits per second is more than enough, and the carrier frequency can be e.g. 100 kHz, which will be much easier to keep inside the wiring (the house is small compared to the wavelength).

For any high-frequency system there are nuisances in the home power lines, e.g. the capacitors in the switching power supplies and fluorescent lights.

Regards, Tauno tauno voipio @ iki fi

We had similar thoughts, but after much fighting with the data transfer, we abandoned the power lines and resorted to a single twisted pair.

See

Tauno tauno voipio @ iki fi

You may want to look at the comp.home.automation group to get an idea of the most popular PLC signal. From my understanding, X-10 is still king and most popular. The patents for X-10 are expired and therefore there are several players competing and providing X-10 type devices. Other formats still have patents and rather limited players on it. In terms of signal, you may want to look for the "Uncle Phil" X-10 chapters which you may find on the internet.

What I understand is that Europe ran into problems concerning PLC commmunications, and rules have been modified that you have to provide rather pure signal (you cannot provide a distorted sign wave because it has harmonics on it). If you look into the Philips chip on PLC, you may note that it provides a rather pure sign-wave (sorry, don't remember the chip number).

Hello, Tauno! You wrote on Mon, 21 Jun 2004 19:45:03 GMT:

??>> In my previous reply I mentioned we are going to use PLC in home ??>> automation project. ??>> What can you say about using PLC in home grid infrastructure ? TV>>> The main competitor is *DSL from the phone companies, which is TV>>> integrable, so there is a definite advantage to DSL side. ??>>

??>> With best regards, Roman Mashak. E-mail: snipped-for-privacy@tusur.ru ??>>

TV> We had similar thoughts, but after much fighting with the data TV> transfer, we abandoned the power lines and resorted to a single twisted TV> pair.

TV> See

Thank you for link. And I have one more question: does every consumer electronics device should have support for PLC ? I mean, even electrical teakettle should have some PLC chip inside to control it?

With best regards, Roman Mashak. E-mail: snipped-for-privacy@tusur.ru

twisted

have

The main problem seems to be that the PLC electronics cannot put into one chip, due to the high frequencies and high voltages in the system.

Tauno Voipio tauno voipio @ iki fi

"Roman Mashak" escribió en el mensaje news:cati17$2e9f$ snipped-for-privacy@mpeks.tomsk.su...

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try Spidcom Technologies, a French company, they are on some technology newspapers