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Post Time: 29/01/2008 13:47:03 |
background hum
Total Forum Posts: 4 |
I live in a high-rise block of flats. One quarter of the ground floor is a substation that supplies the block, plus four neighbouring areas.
It hums/vibrates the concrete structure to at least the fourth floor. This is most noticeable at night. It was re-mounted on some form of isolation, this has helped.
Should the people above it be concerned EMF-wise?
Would a new transformer be any quieter? The current one is apparently 44 years old.
Could the company who maintains it be forced/persuaded to move it into the large grounds?
It was worth the subscription just to get these questions out of my system! |
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Post Time: 30/01/2008 15:36:38 |
alasdairP
Total Forum Posts: 173 |
Hi there. A complicated issue. It does sound as if it is a noisy transformer. Some can be - the metal laminations or the wires in the windings are not totally fixed and vibrate at 100 Hz. All transformers do it to a certain extent. There are agreed noise standards to which distribution substation transformers are meant to comply. Thse websites are helpful:
www.federalpacific.com/university/transnoise/transnoise.html
www.aelgroup.co.uk/hb/hb018.htm
Once you have read through those, I suggest you ask the Energy Network Association in the UK. The ENA are responsible for all electricity distribution in the UK. By all means paste their response here for us to see. Their members have a duty to minimise nuisance, which is probably why the transformer has been re-mounted on rubber (?) isolating mounts.
feedback@energynetworks.org
The transformer could be moved out of the building to a separate enclosure, but it would cost quite a lot of money (between £25,000 and £50,000) so it is unlikelt to happen unless the owner (? Council, Housing Association ?) pays at least half of this cost. A 44 year old transformer cost has to be 'discounted' and so reduces the total cost.
I hope that is, at least, a start for answering your questions. Do feel free to ask more.
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Post Time: 13/06/2008 13:36:02 |
background hum
Total Forum Posts: 4 |
Hello again, all very slow progress here, but a bit more info. It's an 11 Kv distribution sub-station. It's 62.5 db from 2 metres away. Is that noisy or just normal? |
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Post Time: 13/06/2008 21:10:30 |
alasdairP
Total Forum Posts: 173 |
That is fairly normal, but the mix of frequencies that make up the 62.5dBA and whether the noise figure is A-curve weighted makes a big difference to how you can hear it. It isn't just a low "hum", but a hum plus a higher frequency "buzz".
A-curve weighting reduces the value for low frequencies (like 50 Hz and below) as most people don't hear them very well - A-curve is based on the "average" hearing ability of a normal healthy young adult across many populations. Some people can hear (or sense) low-frequencies much more loudly than the normal "average" person and so these can cause them more distress. You may have particularly sensitive low-frequency hearing.
The amount of noise the transformer makes is not related to the EMFs it gives off. The only way to tell EMF levels is to measure them - either yourself or, sometimes, the local electricity company will come and measure them for you. Ask for the "EMF Liaison Officer".
Once a hum gets into a building structure it is almost impossible to actually reduce the vibration.
If the hum is irritating at night and you are not disturbed by a ticking clock, then I would suggest a clockwork alarm-clock near the bed (you don't need to set the alarm!) will cause your hearing sensitivity to decrease and that should considerably reduce the humming that you can hear. If a clock ticking does disturb you, then you can purchase "white noise" generators that put a quiet hissing sound into the room using a small loudspeaker. That has a similar effect in making your body turn your hearing sensitivity down.
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Post Time: 04/07/2008 18:09:09 |
background hum
Total Forum Posts: 4 |
The emf liaison officer is coming out on Tuesday (It's great when you know who to ask for, thanks). Other than taking readings of the underground cable into the substation, the transformer itself and the flat directly above, is there anything else I should point out or ask? I'll post any results.
Thanks for your continuing help |
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Post Time: 28/07/2008 17:00:54 |
background hum
Total Forum Posts: 4 |
All readings are in microteslas:
Substation door 0.52
Flat directly above substation:
Bedroom 0.12
Hall 0.11
Bathroom 0.07
Kitchen 0.07
The report sent with the readings says "the ICNIRP reference levels for the public are 100 microteslas for magnetic fields.
Your thoughts/comments please. |
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Post Time: 28/07/2008 21:34:47 |
alasdairP
Total Forum Posts: 173 |
There is little evidence of problems with mains electricity AC magnetic fields below about 0.15 microtesla (uT), though average UK levels are nearer 0.04 microtesla (about a quarter of that). As long as the block does not have electric off-peak overnight storage heaters, you should be fine. If it does, you need the readings at about 1 AM on a cold winter night to check what the levels are then.
100 uT is to protect against acute effects and specifically not long-term effects such as cancer or dementia. That is made clear in the Guidelines. At present there are no long-term official guidance levels, though 0.2 uT has been used in some Court cases as a guide level that should not generally be exceeded in homes, especially bedrooms.
The latest bau-biologist recommendations are that bedroom levels are below 0.1 uT and ideally below 0.02 uT (though few in cities in the UK are as low as 0.02 uT). See:
www.baubiologie.de/downloads/english/richtwerte_2008_englisch.pdf
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