Previous in Forum: Siemens 3TH42   Next in Forum: Lab Test
Close
Close
Close
34 comments
Rate Comments: Nested
Anonymous Poster #1

Electrical Question

09/21/2013 6:11 AM

which type of instrument is used to reduce the magnetic field of a High voltage transmission line?

Reply
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.
Guru
United Kingdom - Member - Not a New Member Hobbies - Musician - New Member Hobbies - Fishing - New Member

Join Date: May 2006
Location: Reading, Berkshire, UK. Going under cover.
Posts: 9684
Good Answers: 468
#1

Re: electrical

09/21/2013 6:25 AM
__________________
"Love justice, you who rule the world" - Dante Alighieri
Reply
Guru
Engineering Fields - Electrical Engineering - Been there, done that. Engineering Fields - Control Engineering - New Member

Join Date: Dec 2008
Location: Long Island NY
Posts: 15602
Good Answers: 982
#2

Re: electrical

09/21/2013 7:46 AM

Contrary to the rumor you heard, these do not work very well, regardless of the metal used. The key is to direct the magnetic field around the region to be shielded not just between source and sensitive device.

__________________
"Don't disturb my circles." translation of Archimedes last words
Reply
Guru
Engineering Fields - Optical Engineering - Member Engineering Fields - Engineering Physics - Member Engineering Fields - Systems Engineering - Member

Join Date: Apr 2010
Location: Trantor
Posts: 5363
Good Answers: 647
#3

Re: electrical

09/21/2013 8:10 AM

A car.

The further you drive away from the transmission line, the smaller the magnetic field you'll detect from it.

__________________
Whiskey, women -- and astrophysics. Because sometimes a problem can't be solved with just whiskey and women.
Reply
Associate

Join Date: Jan 2009
Posts: 29
Good Answers: 1
#4

Re: electrical

09/21/2013 8:22 AM

Replace transmission lines with superconductors.

Reply Off Topic (Score 3)
Guru
United Kingdom - Member - Not a New Member Hobbies - Musician - New Member Hobbies - Fishing - New Member

Join Date: May 2006
Location: Reading, Berkshire, UK. Going under cover.
Posts: 9684
Good Answers: 468
#5
In reply to #4

Re: electrical

09/21/2013 8:33 AM

How would that affect the magnetic field?

__________________
"Love justice, you who rule the world" - Dante Alighieri
Reply
Associate

Join Date: Jan 2009
Posts: 29
Good Answers: 1
#8
In reply to #5

Re: electrical

09/21/2013 9:13 AM

There would be no magnetic field.

Superconductors use a concentric cable with all three phases placed in a circular fashion like copper tubing of different diameters separated by a dielectric. Due to the arrangement of all three conductors in one cable the magnetic flux of one phase will cancel out the effect of the other phase.

And then you have the Meissner effect that expels all magnetic flux when the superconductor reaches operation temperature. Like the age old question "What would happen if you would drop a magnet down a superconducting tube?" It would free fall when it enters the tube.

Reply Score 1 for Off Topic
Guru
Engineering Fields - Electrical Engineering - Been there, done that. Engineering Fields - Control Engineering - New Member

Join Date: Dec 2008
Location: Long Island NY
Posts: 15602
Good Answers: 982
#10
In reply to #8

Re: electrical

09/21/2013 9:41 AM

You are describing standard magnetic field canceling that comes from twisted cabling. It has nothing to do with superconductivity. Room temperature copper wires twisted together will not generate a magnetic field. Now the logistics of superconducting cables makes gathering them close to each other almost mandatory but this produces many complications from just the simple mechanics of the forces these magnetic fields and cryogenic fluids produce and preventing the magnetic fields from quenching the superconductor.

Besides the OP asked how to reduce the magnetic field from an [existing] transmission line, not how to design a better transmission line.

__________________
"Don't disturb my circles." translation of Archimedes last words
Reply
Guru
United Kingdom - Member - Not a New Member Hobbies - Musician - New Member Hobbies - Fishing - New Member

Join Date: May 2006
Location: Reading, Berkshire, UK. Going under cover.
Posts: 9684
Good Answers: 468
#11
In reply to #8

Re: electrical

09/21/2013 9:46 AM

Oh. I thought you were being serious for a minute. My mistake.

__________________
"Love justice, you who rule the world" - Dante Alighieri
Reply
Power-User
Engineering Fields - Electrical Engineering - New Member Engineering Fields - Power Engineering - New Member

Join Date: Mar 2012
Location: the sandbox
Posts: 341
Good Answers: 6
#6

Re: electrical

09/21/2013 8:45 AM

"which type of instrument is used to reduce the magnetic field of a High voltage transmission line?"

a wire with a grounded shield?

a faraday cage?

a magnetic field reduction device (MFRD)?

__________________
BSEE but always learning
Reply
Guru
Engineering Fields - Electrical Engineering - Been there, done that. Engineering Fields - Control Engineering - New Member

Join Date: Dec 2008
Location: Long Island NY
Posts: 15602
Good Answers: 982
#9
In reply to #6

Re: electrical

09/21/2013 9:29 AM

A simple Faraday cage will do nothing to stop or divert static or slow (60 Hz) magnetic fields. A Faraday cage stops electrostatic fields.

__________________
"Don't disturb my circles." translation of Archimedes last words
Reply
Guru
Engineering Fields - Power Engineering - New Member

Join Date: May 2007
Location: NYC metropolitan area.
Posts: 3230
Good Answers: 444
#18
In reply to #9

Re: electrical

09/21/2013 3:02 PM

Yes, but a complex one will stop both. After all, one of the most common uses of a Faraday Cage is the prevention of propagation and reception of RF energy, which is clearly electromagnetic.

__________________
“Tell me and I forget. Teach me and I remember. Involve me and I learn.” Ben Franklin.
Reply
Guru
United Kingdom - Member - Not a New Member Hobbies - Musician - New Member Hobbies - Fishing - New Member

Join Date: May 2006
Location: Reading, Berkshire, UK. Going under cover.
Posts: 9684
Good Answers: 468
#19
In reply to #18

Re: electrical

09/21/2013 6:40 PM

You reckon a Faraday cage would have much effect on a magnetic field at 50 or 60Hz?

__________________
"Love justice, you who rule the world" - Dante Alighieri
Reply
Guru
Engineering Fields - Power Engineering - New Member

Join Date: May 2007
Location: NYC metropolitan area.
Posts: 3230
Good Answers: 444
#25
In reply to #19

Re: electrical

09/22/2013 10:15 AM

John,

As long as it is constructed from the right materials, basically layers of mu metal and soft iron mesh/sheets. From the Wikipedia article that you referenced above:

"...mu-metal shields are often made of several enclosures one inside the other, each of which successively reduces the field inside it. Because mu-metal saturates at such low fields, sometimes the outer layer in such multilayer shields is made of ordinary steel..."

There was also a discussion in this thread.

__________________
“Tell me and I forget. Teach me and I remember. Involve me and I learn.” Ben Franklin.
Reply
Guru
United Kingdom - Member - Not a New Member Hobbies - Musician - New Member Hobbies - Fishing - New Member

Join Date: May 2006
Location: Reading, Berkshire, UK. Going under cover.
Posts: 9684
Good Answers: 468
#32
In reply to #25

Re: electrical

09/24/2013 3:49 AM

... but it (what you're describing) is not necessarily a Faraday cage, which could (depending on the frequencies it's designed to shield against) be made of chicken wire.

__________________
"Love justice, you who rule the world" - Dante Alighieri
Reply
Guru
Engineering Fields - Power Engineering - New Member

Join Date: May 2007
Location: NYC metropolitan area.
Posts: 3230
Good Answers: 444
#33
In reply to #32

Re: electrical

09/24/2013 10:28 AM

It does meet one of the definitions though:

"...A Faraday cage or Faraday shield is an enclosure formed by conducting material or by a mesh of such material..."

Form follows function. Yes I know, Faraday originally intended it for electrostatic shielding, time has extended its usage.

__________________
“Tell me and I forget. Teach me and I remember. Involve me and I learn.” Ben Franklin.
Reply
Guru
Engineering Fields - Electrical Engineering - Been there, done that. Engineering Fields - Control Engineering - New Member

Join Date: Dec 2008
Location: Long Island NY
Posts: 15602
Good Answers: 982
#34
In reply to #33

Re: electrical

09/24/2013 10:46 AM

No, you are changing the definition of a Faraday shield to suit your opinion. A Faraday shield fabricated from material with a relative magnetic permeability sufficiently greater than unity will also shield magnetic fields inside the shield. There is no specification on the magnetic permeability of Faraday shield material, just that it is conductive.

__________________
"Don't disturb my circles." translation of Archimedes last words
Reply
Guru

Join Date: Oct 2008
Posts: 42355
Good Answers: 1693
#7

Re: electrical

09/21/2013 9:04 AM

A brain that can perform a cursory internet search.

Reply
Guru

Join Date: Oct 2008
Posts: 42355
Good Answers: 1693
#12

Re: electrical

09/21/2013 10:13 AM

At the risk of bursting bubbles and expelling the Meissner effect, there is no instrument, "used to reduce the magnetic field of a High voltage transmission line".

Period: End of story! That's it. Finished.

See ya later, boys.

Reply
Guru
Engineering Fields - Optical Engineering - Member Engineering Fields - Engineering Physics - Member Engineering Fields - Systems Engineering - Member

Join Date: Apr 2010
Location: Trantor
Posts: 5363
Good Answers: 647
#13
In reply to #12

Re: electrical

09/21/2013 10:39 AM

Wrong! An OFF switch to stop the flow of current will work.

__________________
Whiskey, women -- and astrophysics. Because sometimes a problem can't be solved with just whiskey and women.
Reply
Guru

Join Date: Oct 2008
Posts: 42355
Good Answers: 1693
#14
In reply to #13

Re: electrical

09/21/2013 10:41 AM

That, sir, is NOT an instrument.

Reply
Guru
Engineering Fields - Electrical Engineering - Been there, done that. Engineering Fields - Control Engineering - New Member

Join Date: Dec 2008
Location: Long Island NY
Posts: 15602
Good Answers: 982
#15
In reply to #14

Re: electrical

09/21/2013 10:53 AM

They did not say a measuring instrument. All tools can be called an instrument.

__________________
"Don't disturb my circles." translation of Archimedes last words
Reply
Guru

Join Date: Oct 2008
Posts: 42355
Good Answers: 1693
#16
In reply to #15

Re: electrical

09/21/2013 10:56 AM

You are hallucinating. Better get a better hat!

"which type of instrument is used to reduce the magnetic field of a High voltage transmission line?"

Reply
Guru

Join Date: Oct 2008
Posts: 42355
Good Answers: 1693
#17
In reply to #16

Re: electrical

09/21/2013 11:39 AM

OOPS, maybe I'm hallucinating.

I need to lay off the tequila and coffee.

Still if a switch is an instrument, what is a boa constrictor?

Reply
Guru
Engineering Fields - Optical Engineering - Member Engineering Fields - Engineering Physics - Member Engineering Fields - Systems Engineering - Member

Join Date: Apr 2010
Location: Trantor
Posts: 5363
Good Answers: 647
#20
In reply to #17

Re: electrical

09/21/2013 7:19 PM

A stage prop for an exotic dancer.

__________________
Whiskey, women -- and astrophysics. Because sometimes a problem can't be solved with just whiskey and women.
Reply
Guru

Join Date: Oct 2008
Posts: 42355
Good Answers: 1693
#21
In reply to #20

Re: electrical

09/21/2013 7:58 PM

Scottsdale AZ, circa1979. Her name escapses me but she danced with a Boa.

Those were the days. Young, single, good job........................................

Reply
Guru
Engineering Fields - Optical Engineering - Member Engineering Fields - Engineering Physics - Member Engineering Fields - Systems Engineering - Member

Join Date: Apr 2010
Location: Trantor
Posts: 5363
Good Answers: 647
#22
In reply to #21

Re: electrical

09/21/2013 10:10 PM
__________________
Whiskey, women -- and astrophysics. Because sometimes a problem can't be solved with just whiskey and women.
Reply
Guru
India - Member - Sensors Technology Popular Science - Cosmology - Dream, Think and Act United Kingdom - Member - New Member United States - Member - New Member Canada - Member - New Member

Join Date: Aug 2006
Location: AM-51, Deen Dayal Nagar, Gwalior, Madhya Pradesh, MP 474001, India
Posts: 3418
Good Answers: 32
#23

Re: Electrical Question

09/21/2013 11:24 PM

build a house of soft iron walls with windows having iron bars as well. Best design could be like Alcatraz cell holes.

__________________
Prof. (Dr.) Shyam, Managing Director for Sensors Technology Private Limited. Gwalior, MP474001, India.
Reply
Power-User
Engineering Fields - Electrical Engineering - New Member Engineering Fields - Power Engineering - New Member

Join Date: Mar 2012
Location: the sandbox
Posts: 341
Good Answers: 6
#24

Re: Electrical Question

09/22/2013 5:46 AM

shyam said:

"build a house of soft iron walls with windows having iron bars as well. Best design could be like Alcatraz cell holes."

this will work, as long as the roof and floors are also iron or bars. no hole can be greater than 1/4 wavelength (λ/4) in any dimension because RF propagates through holes larger than that.

__________________
BSEE but always learning
Reply
Guru
Engineering Fields - Power Engineering - New Member

Join Date: May 2007
Location: NYC metropolitan area.
Posts: 3230
Good Answers: 444
#26
In reply to #24

Re: Electrical Question

09/22/2013 10:37 AM

If we assume (it really wasn't stated) that the question had to do with AC power transmission lines, then the unadjusted wavelength at 60 Hz (which is not RF) is 1,694,000 ft, a quarter of that (776 +/- miles) is still a mighty big hole!!!

__________________
“Tell me and I forget. Teach me and I remember. Involve me and I learn.” Ben Franklin.
Reply
Associate

Join Date: Nov 2007
Posts: 53
Good Answers: 1
#27

Re: Electrical Question

09/22/2013 1:52 PM

The magnetic field is generated by the current. A transformer raising the voltage will reduce the current for the same amount of power and reduce the magnetic field. That is not really an instrument, but I doubt if you can find an instrument that will reduce a magnetic field and of course the voltage has to be AC.

__________________
Clintb3252
Reply
Guru

Join Date: Oct 2008
Posts: 42355
Good Answers: 1693
#28

Re: Electrical Question

09/22/2013 2:07 PM

A former associate of mine (a PhD chemist) once told me, and I quote, "opinions are like a$$holes. Everybody has one, and most of them stink"!

Credit to, Marshall G_ _ _ _ _.

We constantly prove that here, all of us it seems, do it.

I'm sticking to mine, instruments do not affect magnetic fields.

Reply
Guru
United States - Member - New Member Engineering Fields - Power Engineering - New Member

Join Date: Sep 2006
Location: California, USA, where the Godless live next door to God.
Posts: 4665
Good Answers: 804
#29

Re: Electrical Question

09/23/2013 11:56 AM

You are all wrong anyway (except the statement about opinions). Read the OP again, paying attention to the semantics...

"which type of instrument is used to reduce the magnetic field of a High voltage transmission line?"

The poster did not ask how to reduce the effects of the magnetic field, he wants to alter Oerstead's Law. The only thing that will do that is to reduce the current flow, so the "instrument", if one accepts the concept of aparatus as instruments, would be some sort of high voltage Variac.

I further reject the "switch as instrument" concept because if switched completely off, the high voltage line is no longer transmitting, thereby voiding the semantical premise. By the same token, said Variac would need to limit the reduction only to the lowest point of still being considered high voltage.

All that said, I do enjoy the amount of pointless banter we are allowed to engage in here, often at the expense of one-shot-wonder posts.

__________________
** All I every really wanted to be, was... A LUMBERJACK!.**
Reply
Guru
Engineering Fields - Power Engineering - New Member

Join Date: May 2007
Location: NYC metropolitan area.
Posts: 3230
Good Answers: 444
#30
In reply to #29

Re: Electrical Question

09/23/2013 2:17 PM

JR, You're right, plenty of guess work, especially when it seems clear that the poster put his language through a translator to make the post.

I suspect the OP lives near a power line and was wondering how to "protect" his family in which case we should have told him not to worry. If he's an engineer then the answer is to properly transpose the lines. Even worse, another assumption could be that these are in the air when in fact they could be underground cables, in which case the answer is lay them in trefoil instead of flat, put them in the same conduit, or use a multicore shielded cable.

GIGO still rules until posters are forthright with the conditions surrounding their questions.

__________________
“Tell me and I forget. Teach me and I remember. Involve me and I learn.” Ben Franklin.
Reply
Guru
United States - Member - New Member Engineering Fields - Power Engineering - New Member

Join Date: Sep 2006
Location: California, USA, where the Godless live next door to God.
Posts: 4665
Good Answers: 804
#31
In reply to #30

Re: Electrical Question

09/23/2013 3:41 PM

I think you're right, I was just having some fun with semantics.

I live directly adjacent to 230kV power lines. No cancer, no issues, other than the fact that my Wife is bat s--t crazy. But then again, she was that way before we moved here. I was kind of hoping the EM fields would somehow straighten her up, but alas, the effects of these things are seriously over blown...

__________________
** All I every really wanted to be, was... A LUMBERJACK!.**
Reply
Reply to Forum Thread 34 comments
Copy to Clipboard

Users who posted comments:

1capybara (2); Clintb32 (1); JohnDG (5); JRaef (2); lyn (7); RAMConsult (5); redfred (5); Shyam (1); tiger93rsl (2); Usbport (4)

Previous in Forum: Siemens 3TH42   Next in Forum: Lab Test

Advertisement