Power sub station and me

| > | Andrew - I have been an IT professional for 14 years now. I know how to | > | set my desk up but thanks for the info :) | > | | > | Anyway thanks for the posts guys but the TMJ one is almost certainly | > | correct. I blame my new dentist and the ear plugs going in every night. | > | Still shouldn't be allowed to make that damn noise at night. It's | > | louder than a van running outside the window. | >

| > Could you take a portable audio recorder and start recording this sound, | > starting from inside you house? Periodically talk in a normal voice to | > describe where you are and how far in meters from the substation you are | > as you walk in the best path to go there. Then convert to a WAV file and | > put it online. An MP3 is OK, too, but a WAV file may be important. | -------------------- | | In addition beg, borrow or rent an audio db meter. There are standards and | if you can get recorded and verified noise levels, you have some ammunition | to use. A WAV file does not give a non-objective measure of sound level.

Yep. Ya gotta have a meter so you can try to calibrate the WAV file anywise.

FrediFizzx

postscript

Of course I have, in Kozani where I studied, but it's been more than 8 years.The 400 kV lines were passing just outside the town, and the hum-like noise was annoying.Please note, that voltages equal or below 150 kV don't make corona discharge.

-- Tzortzakakis Dimitrios major in electrical engineering, freelance electrician FH von Iraklion-Kreta, freiberuflicher Elektriker dimtzort AT otenet DOT gr Ï "Don Kelly" Ýãñáøå óôï ìÞíõìá news:pBehe.1344077$8l.399901@pd7tw1no...

electromagnetic

Please tell me where in scotland u are ....

Or the SubStation name.

I can then tell you if the Local electrical company will examine your noise complaint or indeed the EMF levels.

I have witnessed this several times and cured the noise by mounting the Tx on 3" of rubber matting.

let me know here ASAP.

PS

Sub station name is on a plate on the gate. "

Why do you think that lines below 150KV don't have corona discharge? Sometimes they are worse than higher voltage lines because corona is not taken into account in their design and construction. One of the noisiest lines (at least for RF from corona)that I have known was a 66KV line Since I was in a car, I can't comment on audio noise for this line. Corona "pinwheels" work quite nicely at 10KV DC.

It's a matter of field intensity and non-uniformity of the field rather than absolute voltage level. What would lead to breakdown in a uniform field leads to corona in a non-uniform field. The corona discharge from lines can be due to many factors and designof HV lines holds fair weather corona to a low level. Discharges during snow storms can have little hum component but a great deal of high frequency hiss and sputter (this may not be noticed in rain as the rain noise may drown it out-snow is quieter). It is true that there is a second harmonic hum but the most noticable noise is the broad spectrum , quasi-white noise which occurs.

If your 400KV line has appreciable corona noise under fair weather conditions, then it is poorly designed, poorly built, conductors dragged in the sand during construction - or the insulators were pretty dirty. Might I suggest that the "hum" that you heard might not be corona related?

Of course the highest voltage substation that I have been in was only 765KV (during a snow storm) and the highest that I have personally played with in a lab was about 300KV to ground and there was no problem in getting audible and visible corona below 150KV.

Don Kelly snipped-for-privacy@peeshaw.ca remove the urine to answer

|> | Andrew - I have been an IT professional for 14 years now. I know how to |> | set my desk up but thanks for the info :) |> | |> | Anyway thanks for the posts guys but the TMJ one is almost certainly |> | correct. I blame my new dentist and the ear plugs going in every night. |> | Still shouldn't be allowed to make that damn noise at night. It's |> | louder than a van running outside the window. |>

|> Could you take a portable audio recorder and start recording this sound, |> starting from inside you house? Periodically talk in a normal voice to |> describe where you are and how far in meters from the substation you are |> as you walk in the best path to go there. Then convert to a WAV file and |> put it online. An MP3 is OK, too, but a WAV file may be important. | -------------------- | | In addition beg, borrow or rent an audio db meter. There are standards and | if you can get recorded and verified noise levels, you have some ammunition | to use. A WAV file does not give a non-objective measure of sound level.

Actually, I wasn't looking for sound level, thought it could give some degree of relative measure. Instead, I would check spectrum and waveform.

Do you confuse corona with insulator leak current?Insulator leak current appears even at 15 kV, the insulators of the substation just around the corner that feeds my neighborhood even explode after a long, dusty summer and especially in the first rains.Corona has nothing to do with insulators or the uniformity of the electric field, it has to do with the strength of the electric field, in voltages of 220 kV and above, around the conductor, and well away of the insulator.The uniformity of the electric field plays a role in medium voltage (10 to 25 kV) underground cables, where every live conductor has a shield, or the insulation will break down.

-- Tzortzakakis Dimitrios major in electrical engineering, freelance electrician FH von Iraklion-Kreta, freiberuflicher Elektriker dimtzort AT otenet DOT gr Ï "Don Kelly" Ýãñáøå óôï ìÞíõìá news:85She.1363218$6l.341714@pd7tw2no...

Can you confirm where you are and what the ss name is please

it will be on the gate or door

John C

( leccy board engineer)

------------- I know the difference between corona and leakage. Corona can occur on insulator strings or surfaces where parts are conductive and parts are clean. As for uniformity of the field, my comments stand (do you think the surface field across an insulator or insulator string , is uniform? ). Conditions that, in a uniform field would lead to breakdown, can and will produce corona in a non-uniform field. Corona IS a factor dependent on the non-uniformity of the field as well as its strength. (i.e. Ionization starts in a high field region and propagates but further out the field intensity is too low to support ionization so one gets Trichel pulses, streamers etc . In a uniform field this would not happen but breakdown would occur as the ionization would extend throughout the gap. Strength and uniformity of the field are both factors. Gallager & Pearmain "High Voltage-measurement, testing and design, is one reference, Peek is a classical reference and there are references in the "EPRI 345KV and above" book. Note the following:(p50 gallager et al) "Where there are points, sharp edges, surface roughness or curvature of small raddius, the stress on the gas can be enhanced by 10 times with respect to the average stress" (attributed to Lewis 1955, "High field electron emission from irregular cathode surfaces" J. Appl, Physics 26,

1405-1410 ) Nicks on the surface of a conductor are corona sources. This is well known. On low voltage lines the tips of the wires that are used to tie the conductor to the insulators can cause corona- again well known. In cables, internal corona can occur because of void formation due to thermal expansion and contraction and shields will not prevent this -also well known.(Note that high voltage cables are pressurised, in part to avoid this).

. Nor will the lack of shields necessarily lead to breakdown-This depends on other factors as well. (Gallager, et al p189, 190) dealing with unshielded and shielded polyphase cables, gives the reason for the use of shields as well as the void problem, independent of shields, as mentioned above.

As to the insulator failures- Dust (particular in seacoast regions) + rain - you said it. . Corona may or may not be present . Insulator explosions seem to indicate that the insulators may have had some damage -even hairline cracks - such that in the dry times the insulation was fine but add moisture and bang-up she goes. A sound insulator should flash over on the surface (non-destructive) before breakthrough failure (destructive). Unsound -and it's a gamble. I would suggest that climate and location have a strong effect on this.

Also note devices which make use of corona such as precipitators operating in the region of 50KV and there have been domestic electrostatic filters, speakers, and ozonators which use corona and operate at well below this level.