Comment So what ? (Score 1) 96
Ok, so you have a big transformer near your backyard. Why should you consider it a problem ? Aside from the fact that "big" is a relative term (for train power it cannot be that big, since these are most likely in the 6-12 kV range, certainly not as one found attached to a EE transport backbone), what is of importance here is the fact that the frequency of the electric and magnetic fields is 50 Hz (oops, forgot you are in the USA, make that 60 Hz) and its 3rd and 5th armonics, hence, for you, 180 Hz and 300 Hz, because these are the non-negligible frequencies of the fields you get from a powerline.
Frequency is relevant because with it you have the wavelenght of the field and, in order to decide if the field is dangerous to your health, you have to compare this lenght with the dimension of your cells. Since at 50-60 Hz the wavelength is in the range of thousands of kilometers (and for 300 Hz it's not that much shorter) it's easy to see that you don't have a problem living near one of these things.
This is the exact same reason why cellphones are much more suspicious and why x-rays are confirmed to cause cancers: their frequency (around 10^24 Hz, IIRC) implies the wavelength is much shorter than a cell, making them able to damage it.
The reason this is relevant is because, with long wavelength, the [magnetic | electric] potential at different points in the cell is identical, while with short wavelengths it is not: in this case you have [magnetic | electric] currents that run through your cells (organic tissues are conductive, so you can use the simple model of an impedance), and with current you have heat, inducted currents, parasite currents, etc...
Even for really high voltage lines (i don't know the operative voltages in the USA) there is no issue: in Italy we divide voltages in 3 ranges: 220-380 volt is low voltage, 4.5-23 kV is medium voltage (secondary distribution stations, trains, production plants), and the three high voltages: 130 kV (primary distribution stations), 220 kV and 380 kV (backbones, power plants connections); only for the high voltages, there is a rule of thumb to follow: when you are farther out from the powerline than 5 meters plus 1 centimeter for kV, you are well in the safety area (so for a 380kV line you have to be at least 8.8 meters from the wires; if you are directly under the line, but it's high in the sky, you are clear).
Bye,
Alberto
Frequency is relevant because with it you have the wavelenght of the field and, in order to decide if the field is dangerous to your health, you have to compare this lenght with the dimension of your cells. Since at 50-60 Hz the wavelength is in the range of thousands of kilometers (and for 300 Hz it's not that much shorter) it's easy to see that you don't have a problem living near one of these things.
This is the exact same reason why cellphones are much more suspicious and why x-rays are confirmed to cause cancers: their frequency (around 10^24 Hz, IIRC) implies the wavelength is much shorter than a cell, making them able to damage it.
The reason this is relevant is because, with long wavelength, the [magnetic | electric] potential at different points in the cell is identical, while with short wavelengths it is not: in this case you have [magnetic | electric] currents that run through your cells (organic tissues are conductive, so you can use the simple model of an impedance), and with current you have heat, inducted currents, parasite currents, etc...
Even for really high voltage lines (i don't know the operative voltages in the USA) there is no issue: in Italy we divide voltages in 3 ranges: 220-380 volt is low voltage, 4.5-23 kV is medium voltage (secondary distribution stations, trains, production plants), and the three high voltages: 130 kV (primary distribution stations), 220 kV and 380 kV (backbones, power plants connections); only for the high voltages, there is a rule of thumb to follow: when you are farther out from the powerline than 5 meters plus 1 centimeter for kV, you are well in the safety area (so for a 380kV line you have to be at least 8.8 meters from the wires; if you are directly under the line, but it's high in the sky, you are clear).
Bye,
Alberto
