Broadband through power lines...

[sao123]

large chance of a surge suddenly destroying your entire network...?
elecrocuting yourself...?

 

[harrkev]

Both of those are posibilities, but they are posibilities without BPL. To me, the real problem is with spectrum polution. BPL uses frequencies below 80MHz to send the data. So, you have a modulated signal going over a very long wire.

An antenna consists of a modulated signal going over a long wire.

So, all of a sudden, radio frequencies below 80MHz start to show a lot more noise. Those frequencies are used for the following: Ship communication, amateur radio, commercial shortwave, and many defence, safety, and law enforcemnt services.

The frequencies belode 50MHz (especially below 30MHz) are the only radio signals that can go around the Earth. Higher frequencies are "line-of-sight" only, so the only way to get a higher-frequency signal to go around the Earth either requires cables or sattelites.

The reason that BPL is so bad is that the power lines are unshielded. Cable television goes over coax lines, where the signal is in the middle of the wire, and the wire is surrounded by a metal shield.

 

[brentkiosk]

I agree with harrkev. The danger to your system from a power surge or to you from electrocution with BPL is probably no greater than it already is without BPL because you use electricity from the power company. The real problem is spectrum pollution.

There have been several pilot BPL programs, and none has been able to successfully reduce radio interference (I don't have a web address reference - I saw it in print). BPL uses the radio spectrum up to about 50 MHZ, which means that power lines are being asked to act as RF transmission lines in this frequency range. Power lines were never intended for this kind of service, and they are leaky. Both phone and cable lines are designed for signal as opposed to power transmission, and don't leak much.

 

[Jeff7]

Something else comes to mind - say you or a neighbor has a grid-tie power inverter, running off of solar or wind power. Might that be detrimental to the data signal?
As I understand it, "pure sine wave" inverters still don't put out a pure sine wave - it just has a whole lot of tiny steps in it, and is considered "close enough" to be called a sine wave. So while they get pretty damn close, there's still a slight amount of distortion.

 

[imported_Soldier]

You guys have it all wrong. First off broadband on power lines is primarily a fiber cable build anywhere outside the home, so your concern about interference from outside signals is unneccessary. In home the problem is no more or less important than it is to any guy with an antenna on his roof, outside of close range interference from things like microwave ovens its a non-issue. The inhome broadband over the house powerlines is heavily grounded and filtered so outside interference is kept well below the point of causing problems. The big issue with broadband over power is the power compainies lack the financial clout to build out the fiber portions to get to each home.......in other words dont expect it anytime soon.

 

[brentkiosk]

Inhome broadband over house wiring is not the source of the spectrum pollution problem. It's the access BPL signals that have caused trouble in most of the pilot programs (many of which have been discontinued for a variety of reasons). Access BPL works by inductively coupling a data signal to the medium voltage power lines. These are the ones at the top of the poles which run at several thousand volts. The signal is carried as RF on the MV power lines most of the distance it travels. Since the RF signal cannot make it through the transformers used to step the MV level down to 240 volts for home use, another system - fiber cable or maybe wireless - is used for the last little bit to your house. It's the incidental radiation from the MV lines that has been difficult to reduce below the levels specified by part 15 of the FCC regulations so far. I think next generation hardware may already be under trial, however, and the spectrum pollution question could be resolved. But, as Soldier points out, there are other issues and you probably won't see BPL anytime soon.

 

[harrkev]

Originally posted by: brentkiosk
I think next generation hardware may already be under trial, however, and the spectrum pollution question could be resolved.

I doubt it. The problem exists 100% in the fact that data is sent using unshielded wires. If you send data, you HAVE to modulate a signal, which meand that a spectrum will be produced. Since every bit of spectrum is owned, any radiated energy will step on somebody's toes. If they shift to a higher frequency (100MHz or above), then the effects will be localized to the city and/or neighborhood, but if every neighborhood has this, then the problem will be everywhiere.

There is no "magic bullet" or "trick" that can get around this. The ONLY way to send any sort of high-rate data without interference is to use a shilded cable, twisted pair, or optical. It is also possible that burying the cable would help, too.

 

[brentkiosk]

Harrkev - I also doubt it, but had read that Bendix was going to try a different system that showed promise compared to the Amperion hardware that didn't work. My personal opinion is that this is not a good way to extend broadband to remote regions for exactly the reasons you said. It is hard to believe that treating power lines as an RF transmission line that doesn't radiate can work. Also, noise from the power I and V will be a problem, so fairly frequent repeaters/amplifiers/signal conditioners will be required even if the lines are in good condition. When they are not (I live near some bad insulators, so I know they are not always quiet) the digital signal could suffer a lot of errors. Almost any other system seems to me to have advantages over BPL. But, if someone wants to solve the engineering problems (or prove that it's not worth it) they ought to try at their own expense.

 

[bobsmith1492]

A huge network of antennas... wowzers. Don't solar flares already wreak havok on the power grid? Imagine what would happen to your connection....

 

[imported_Soldier]

Hmmm maybe I did not say it correctly so I will try again. Most current proposals around BPL service envisions fiber optic cable lines using power company interstate towers and right of ways. These will hit ditributuion style networks on the local (town or city) level and also run along exsisting power company rights of way and pole lines. The plan is to integrate the fiber cable in either an overlashed fashion or to just run all new cable as part of the build out. If all new was placed it would run in the power companies gain but not be in contact with the regular power transmission lines. Fiber would then be dropped to each house as needed via a passive (read that as zero power influence) splitter/combiner device placed at the serving pole. Power for the in home "modem" would come from the same plug that introduces the data stream to the home wiring.

No ones is seriously considering trying to overlay data on metalic power lines these days, at least not outside the home or business. The expense of filtering and jumping through or around each transformer out on the street would be in excess of simply building a fiber overlay of the current network....

 

[brentkiosk]

Originally posted by: Soldier



No ones is seriously considering trying to overlay data on metalic power lines these days, at least not outside the home or business. The expense of filtering and jumping through or around each transformer out on the street would be in excess of simply building a fiber overlay of the current network....

I wish what you say were true, but that's exactly what one form of BPL means, and I think that's what OP was referring to. Using existing towers, etc to support sheilder or fiber cable wouldn't cause anyone any trouble, but the several pilot programs that ran recently and may still be in operation actually used the metal power lines to carry a modulated RF signal up to about 50 MHZ. As you would expect, there was measurable interference to reception of various radio services in this frequency range for receivers fairly near the power lines.

Text has a summary.

 

[PowerEngineer]

Power companies are anxious to take advantage of other services that can be delivered using the right-of-ways already acquired for power transmission/distribution. One way do to this is to string fiber (as Soldier says), either separately or actually in the core of shield wires or actual conductors.

It's also true, however, that power companies would like to use their existing distribution systems (which are in effect wave guides for very low frequency EM radiation) to directly carry broadband internet service. The internet service is superimposed on a much higher frequency carrier that effectively shares the conductor with the 60 Hz power. The small amplitude high frequency "noise" does not really affect your regular AC powered devices, and the internet service is pulled off the wire by a device not unlike a radio that is adjusted to the carrier frequency.

As has been mentioned earlier, these high frequency signals get filtered out when passing through the power transformers. That's why one of the better attempts has had the power companies applying the internet signal at the substations after the voltage has been stepped down to distribution levels (normally 11 to 13 kV) and runs up and down streets throughout the area. The problem is that it has to pass through another transformer to step down to 240 volts. So to get the signal to the customers, the internet signal is taken off at the distribution voltage level and relayed to customers via fiber or by short-range wireless transmitters.

I agree that EM noise pollution is a valid concern.

 

[sao123]

Originally posted by: brentkiosk

Originally posted by: Soldier



No ones is seriously considering trying to overlay data on metalic power lines these days, at least not outside the home or business. The expense of filtering and jumping through or around each transformer out on the street would be in excess of simply building a fiber overlay of the current network....

I wish what you say were true, but that's exactly what one form of BPL means, and I think that's what OP was referring to. Using existing towers, etc to support sheilder or fiber cable wouldn't cause anyone any trouble, but the several pilot programs that ran recently and may still be in operation actually used the metal power lines to carry a modulated RF signal up to about 50 MHZ. As you would expect, there was measurable interference to reception of various radio services in this frequency range for receivers fairly near the power lines.

Text has a summary.

It is indeed what I was referring to. There was an article in Networking Computung on 6.9.2005 on page 81, portions can also be found here.

Article Cliffs...
Electric uses 3 types of lines... high voltage, medium voltage, & low voltage.

Data signal will not travel over high voltage lines because of interferernce.

Fiber cable is run from the ISP to the substations where medium voltage lines begin.

Data runs over medium voltage lines, using a wired coupler or a WAP to bypass transformers which would interfere with the signal.

Data runs through the low voltage lines directly to all electrical outlets in your house.

optional: some people who live close enough to medium voltage lines, may be able to get internet through the transformer bypassing WAP's.

Primary problem with PBL now: max 56bit encryption.

 

[imported_Soldier]

I will only say that Ive been in the telecom industry for a long time, and Ive seen all sorts of schemes come and go. Current wisdom says the amount of money involved is usually a good indicator of how serious a person or corporate entity is about a particular project. Unfortunately this idiom does not hold in the telecom or utility industries. I have seen literaly hundreds of millions of dollars, and in one case over a billion, spent on the next best thing; only to have the plug pulled just when some of the tougher issues are about to be resolved. Broadband Over Power has the look and feel of a "pie in the sky" dream, in other words dont hold your breath.

 

[AdamNuhfer]

As a Electric Company employee, we have in the past few years replaced a number of our steel cored aluminum neutral wire with newer wire with fiber optic cable inside. This has been installed on the large Extra high voltage structures along with distrubtion structures. Idea being we would use a couple strands of the fiber for ourselves and rent the rest out making big buks. Or so it was supposed to go that way. Others had the same idea and now, we have a glut of excess fiber. Ma Bell in Pittsburgh PA is doing a trial with Fiber run right into the house to see how well it works. Lots of fiber out there, but getting into your home, well, that's a different and costly investment that they will look long and hard at.

 

[imported_Soldier]

Exactly what I meant, pie in the sky. Actual fiber use is only about 5% of total capacity in field for the US. It's not that BPL is a bad idea, the real question is who needs it? And why bother.