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| Request for knowledge - Troubles at home |
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| nctnico:
--- Quote from: EEVblog on July 02, 2022, 09:19:55 am --- --- Quote from: lxmute on July 02, 2022, 07:31:07 am ---Hello, Your replies where helpful to bring me back to the "sound aspect" problem. Requesting help from a specialist in EMI and its derivatives, I've been led to the problem of Infrasounds generated by harmonics inducted by high power + high frequencies (moderated since in 90kHz range) at a low frequency range on unshielded city grid cables. --- End quote --- Err, how do the city power cable induce low frequency sound? What is the physical mechanism? Sorry to tell you, but it sounds like you have been peddled some BS :bullshit: --- End quote --- Pass enough current through a cable and it will start to move due to the magnetic field. Lookup some videos about arc melting furnaces. You can see the cables dance around. The same can be seen from cables going to spot welders. Heck, I even managed to make test leads move on my desk by discharging a capacitor bank causing a 1kA current spike. All in all it is possible that cables move or vibrate. |
| ebastler:
--- Quote from: lxmute on July 02, 2022, 11:09:54 am --- --- Quote ---That's what I thought... Also, where is the 90 kHz carrier supposed to come from --- End quote --- http://scent-itn.org/emi_cenelec_freq.html --- End quote --- Yes, power line communication is a thing. But those signals are not "high power". Even in the presence of non-linear effects, which could in principle generate sub-harmonics, I struggle very much to see how they could induce noticeable audible or sub-sonic frequencies. You are barking up the wrong tree. The multiple earlier posts which were encouraging you to look into low-frequency vibrations, were trying to lead your thinking away from the EMI you were so concerned about. We were talking about the possibility of purely mechanical vibrations introduced from the bakery. You somehow managed to connect this back to your favorite concerns about EMI again, which I think is misleading you. --- Quote ---A last note, there is a bloom in France of people being hardly hit by infrasounds, on the whole territory. Which ignited 2 years ago my curiosity. --- End quote --- Mass hysteria? ??? (There's a peculiarity here with English, by the way. "Hardly" means "barely, not much at all". What you probably mean is that people were "hit hard" or "hit heavily" by infrasound. Although I believe that what you accidentally wrote, namely that they were "hardly hit", happens to be correct. ;)) |
| nctnico:
--- Quote from: ebastler on July 02, 2022, 12:51:27 pm --- --- Quote from: lxmute on July 02, 2022, 11:09:54 am --- --- Quote ---That's what I thought... Also, where is the 90 kHz carrier supposed to come from --- End quote --- http://scent-itn.org/emi_cenelec_freq.html --- End quote --- Yes, power line communication is a thing. But those signals are not "high power". Even in the presence of non-linear effects, which could in principle generate sub-harmonics, I struggle very much to see how they could induce noticeable audible or sub-sonic frequencies. You are barking up the wrong tree. The multiple earlier posts which were encouraging you to look into low-frequency vibrations, were trying to lead your thinking away from the EMI you were so concerned about. We were talking about the possibility of purely mechanical vibrations introduced from the bakery. You somehow managed to connect this back to your favorite concerns about EMI again, which I think is misleading you. --- End quote --- I agree with this. The problem is most likely to be acoustic. A good first step is to use vibration sensors to measure if, where and how the house is vibrating. |
| Coordonnée_chromatique:
--- Quote from: EEVblog on July 02, 2022, 09:19:55 am --- --- Quote from: lxmute on July 02, 2022, 07:31:07 am ---Hello, Your replies where helpful to bring me back to the "sound aspect" problem. Requesting help from a specialist in EMI and its derivatives, I've been led to the problem of Infrasounds generated by harmonics inducted by high power + high frequencies (moderated since in 90kHz range) at a low frequency range on unshielded city grid cables. --- End quote --- Err, how do the city power cable induce low frequency sound? What is the physical mechanism? Sorry to tell you, but it sounds like you have been peddled some BS :bullshit: --- End quote --- It seems to be a misinterpreted resurgence of a blurry souvenir : https://www.researchgate.net/publication/320106708_Low_Frequency_Oscillations_in_Large_Power_Grids |
| lxmute:
Thank you, I will read this document. Can a 65kV power grid transformer be considered as « high power », enough for this ? I'm also wondering about neighborhood 20kV transformers. Call me weirdy if you want, but there is a transformer 500m away, cables hidden into the ground. As the cable path is covered by new asphalt, you can clearly see its path. If I stand on that cables path, I feel under foot exact the same rythmic hassle as in my desk room. As I'm wondering a bit about high power and how transformers are working, concerning all those neighborhood transformers, are they weighted by some barycentric law to handle a working stability altogether ? Strange things happened in 2020 here, 3 walls just next to 3 transformers felt down. Then feb. 2020, the wall of a transformer just split in two parts, the 20kV transformer within exploded. :-+ I'm learning a lot by your objectivity, comments and doubts in the end, which is always good. Thanks. |
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