[ecrabb]

Today, they're digging the basement of our new home theater that includes a house built around it. I was at the site today and noticed a very large electrical service drop that runs to a transformer behind the neighbor's house. I assume it feeds the 6 or 8 houses nearby, but I have no idea. The transformer is a cube about 3' on a side. The drop itself is in PVC about 6" in diameter. What bothers me is that it runs the length of one side of the house about 3-4' from our foundation, and 3' or so below grade. My bedroom window will be just above. When I sleep, my head will probably be 8' or so from that drop.


Is my hair going to fall out? Will I hum songs to myself uncontrollably, but only at 60hz? Will I become sterile? Perhaps most important, will I have trouble with the projector or AM radio reception? The HT will probably be less than 20' away from that thing, and the projector not much further. Do I have anything to worry about? Any informed or even uninformed opinions are welcome.


SC

 

[Tim in Phoenix]

Sir


As long as you are 50+ feet from the transformer you are probably okay regards magnetics; the cables in the ground are likely no threat.

 

[ecrabb]

Hmm... uh oh. The closest corner of the basement is probably 40' or so from the xformer - they're very compact lots and houses. That probably puts the projector in the 50-60' ballpark from the xformer. Crap, is this going to give me trouble? Please don't tell me I won't be able to use my CRT.


How much magnetic radiation do those things give off, anyway? It's pretty loud standing right next to it - clearly audible 60hz hum. I figured it was loud enough to hear it from inside the neighbor's garage only a few feet away. Maybe not with insulation in place, but still...


I'm going to run by there on the way home and step it off. Thanks for the help.


SC

 

[Larry Fine]

I'd like to know what happened to the 45-minutes of typing a response to this that disappeared when I submitted it, and the forum was unavailable for the last hour or so.


Anyone?

 

[Larry Fine]

Okay, now that I'm no longer pissed, I'll try again, but a little shorter.



Since we live in electrified cages anyway (picture your houses wiring as if the walls were transparent), biological effects wouldn't be my first concern.


How did you discover the conduit? Is it just sheer luck that nobody was electrocuted? What about setbacks and utility rights-of-way? Will you be able to safely dig on your own property?


The transformer hum is caused by the construction; laminated steel is known to "sing" because of the magnatic fields and eddy currents. Didn't you know the transformer was there when you bought the property?


One good point: You'll have less voltage sag with such a short service lateral.

 

[filecat13]

IT SOUNDS LIKE EVERYTHING WILL BE (caps lock off now, sorry) fine. Avoid overthinking the situation or you might end up imagining things that aren't even there.


Larry makes the most compelling argument: you're already surrounded by the grid anyway. (Kinda like the Matrix in juvenile form).


I know that in S. Korea 220 is the norm, as is Britain, so don't worry that 220 or even 440 nearby is somehow worse interference-wise than 110. (Larry, what's likely to be running in that conduit?) People around the world live with higher voltages close by with no ill effects to themselves of equipment. Now if you were under the big power lines, that'd be something else.

 

[ecrabb]

Thanks for the replies, guys.


Larry -

Damn, I want to see your post that you spent 45 minutes writing!!! Yes, I noticed the transformer before, but it was behind big piles of dirt and it seemed so far away when the lots were just dirt. Now that the hole is dug, it seems a lot closer. Right now, it probably seems worse than it really is because of the over-dig. Also, I had no idea the big utility feed ran right around the corner of my lot, either - until they dug the hole.


It's no miracle that no one was electrocuted because a builder is building my house and the developer's engineer probably told the excavation crew exactly where they could dig and knew exactly where the drop was! ;-) Seriously, the reason things are so tight is that my house will sit on a corner lot of a "townhouse" style development. The lots are negligibly larger than the houses themselves, and my house in particular has a very big footprint due to the design of the house. To get a better idea of what we're doing, you can look at this page:

The house sketch page

The page is kind of a hog - make sure you're not on dialup.


In the site plan, the pink "U" house is ours, and the xformer is behind the "M" house next door.


Basically, the lot is my favorite lot, and the house is my favorite design. Nobody else in my little town is doing anything remotely similar and I wasn't going to choose a different house because there was a transformer nearby. Maybe if it had been outside my window, I'd be thinking differently - I don't know.


As for the other stuff, yeah, I know the walls have 120 and 240 running all over in them - I was just concerned about a giant bundle of 440v (or whatever it is - anybody know?) running right by the house. I wasn't seriously concerned about biological effects - I was mostly trying to be funny. Actually, I'm not freaking out or anything - I was just concerned and wondering whether it might be a problem for the CRT or just A/V in general. If it won't be, I won't worry about it.


Thanks for input.


SC

 

[aspec2]

Hmmmmm....sounds like an opportunity. Some big wire wrapped around the pipe....free power???? Don't get caught.


Walt

 

[deronmoped]

As long as you are in the basement you will be safe from your biggest threat of electromagnetic radiation. The Death rate for it right now is like 10,000 a year. Stay in the basement out of the Sun and enjoy some movies


Deron.

 

[hi_l2es]

The real threat to our health comes from being exposed for long periods of time with close proximity to the huge high voltage tension lines that are used to distribute our power to us. Voltage of 66 - 132 kV is used to reduce the power loss on the transmission lines for long runs. This high vlotage is transformed to a medium voltage of 10 - 50 kV and then transformed by sub-stations again to the low voltage we use of 220 - 440 V depending on whether it is being used for industry or home.


You can usually use RF to identify noise created by leaky transmission lines because they transmit more RF when they are leaking. Generally, you can walk around your property with an AM radio tuned to 600 KHz and will hear a loud buzzing sound which is actually low frequency RF if you have a problem. New neighborhoods generally do not have this problem; but it can happen because of faulty parts, or shabby installation.


Usually you can walk right up to the offending transformer, or pole where the problem is by listening to the intensity of the sound or the signal strength if your radio has a signal meter in it. If you do have a strong / loud buzzing sound call the Power Company and tell them they have an energy leak in your neighborhood that is is interfering with your AM reception. They usually respond and repair it with no problem.


I personally want the Builders, that put houses under High Tension lines, put in jail along with the government officials that allow it to be done.


220 - 440 V can be irritating sometimes as a noise source but is not going to hurt anyone's health to my knowledge.


PS: My power transformer is ground mounted in my yard with underground wiring to the house. It is hidden by shrubbery about 100 feet from the from the front right side of the house. I like it there because I can watch it and will notice a problem quicker if, or maybe I want to say when it occurs. It has never caused me a problem to date - 22 years. When I was using large beam antennas for RF communications my experience that when I heard electrical noise it was typically something like a neighbor's refrigerator going bad - lol.

 

[Larry Fine]

Actually, the 10 to 50 Kv is the primary distribution voltage that leaves the sub-station. This is what you see atop the typical power pole, and is fed via a fuse into the utility transformer. It doesn't become 120/240, secondary voltage, until it leaves the transformer and is sent to each house.


Pad-mounted transformers use the same voltages and basic pattern. The difference is that direct-burial cable is used, and each house's secondary goes individually from the transformer to the house. The conduit is used primarily as physical protection, such as when run beneath a road.


The cable in the conduit is most likely the primary feeder, in the 10-50 Kv range; 17.7Kv is a typical voltage around here. Primary underground cable is usually coaxial in construction, with bare strands spirally-wrapped around the high-voltage insulated single conductor.


The bottom line is that the actual risk of incidental hazards is small; my point was that the physical proximity of the cable to the yard would matter more. To be honest, my transformer is at the back of my yard, about 40' from the house. I don't sweat it; I like modern life too much.

 

[filecat13]

Thanks for the electrifying summary.

 

[Prometheusbound]

Thats interesting Larry, I have never heard of 17.7. We have 12470 and 13800 as the main primary voltages here. Most of our high tension cable no longer use a concentric neutral but use a foil shield with a semiconducting jacket.


ecrabb, you really have nothing to fear from that conduit as far as EMR is concerned. I agree that it is most likely a primary feeder. Since the feeder conductors are being carried in a common pipe and the current draw on them will be relatively equal, they will cancel each other out and the amount of EMR will be very very small. This is in fact the reason why they are all put in the same pipe. If you ran the different phases in different pipes something interesting would happen. They would get VERY hot. Also in the grand scheme of things the current draw by the bug(transformer) is very small, another reason why you have little to fear.


Charles

 

[RadDoc]

Steve --


I may be uniquely qualified to address your electromagnetic radiation concerns:

• Homeowner
• HT Enthusiast
• CRT Owner
• Electrical Engineer (undergrad)
• Parent (...and, the wife's been fixed)
• Physician
• Radiation Oncologist

My prescription: Quick -- give your home and theater to me! I'm already bald, and if I get cancer, I can cure myself...


Seriously, there's no significant health hazard: http://www.niehs.nih.gov/emfrapid/ht...T/DEMF18fT.htm

 

[JVanderwalker]

I would not worry about magnetic coupling at that distance to your PJ deflection since the magnetic field intensity drops as a cube of the distance. As for the physical effects I agree there is no correlation to powerline magnetic or electric field and health effects even with high tension lines. What the power companies don't want to say is for many years defoliants like agent orange was used in the vicinity of these towers. I am sure RADDOC would agree this can be correlated to heath effects.

Jim