ECN Electrical Forum - Discussion Forums for Electricians, Inspectors and Related Professionals
ECN Shout Chat
ShoutChat
Recent Posts
Increasing demand factors in residential
by gfretwell - 03/28/24 12:43 AM
Portable generator question
by Steve Miller - 03/19/24 08:50 PM
Do we need grounding?
by NORCAL - 03/19/24 05:11 PM
240V only in a home and NEC?
by dsk - 03/19/24 06:33 AM
Cordless Tools: The Obvious Question
by renosteinke - 03/14/24 08:05 PM
New in the Gallery:
This is a new one
This is a new one
by timmp, September 24
Few pics I found
Few pics I found
by timmp, August 15
Who's Online Now
1 members (Scott35), 261 guests, and 17 robots.
Key: Admin, Global Mod, Mod
Previous Thread
Next Thread
Print Thread
Rate Thread
Page 2 of 3 1 2 3
#123996 06/28/06 12:31 AM
Joined: Oct 2000
Posts: 2,723
Likes: 1
Scott35 Online Happy OP
Broom Pusher and
Member
Quote

For effect, have someone hold a fluorescent tube under the lines.

Definitely will display the overall field effect taking place at this location!

The Lamp will illuminate - possibly near 1/3 of the intended output.

Scott35


Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!
#123997 06/28/06 01:12 AM
Joined: Mar 2006
Posts: 52
T
Member

#123998 06/28/06 03:40 AM
Joined: Dec 2005
Posts: 869
Likes: 4
R
Member
Those lines look to carry a higher voltage than 72 kV to me.
More like 132 or 275 kV looking at the strings of disc insulators.
We use 12 for 220 kV in NZ this looks like 16 discs to me ( 275 kV ? )

Very likely that magnetic fields induce eddy currents in the steel tent poles and cause a possible voltage build up.

What are the Grid / POCO poles made off, concrete or steel ?

A possibility is that one Grid / POCO pole is partially live due to a faulty insulator string, either in the steel or via the reinforcing steel.

Might pay to get the Grid / POCO asset owner to check out their poles for leakage and check up with the local regulations re safe working distances for temporary buildings, tents near these lines.

If to close, this is a very dangerous situation.


The product of rotation, excitation and flux produces electricty.
#123999 06/28/06 07:49 PM
Joined: Mar 2006
Posts: 52
T
Member
Rodalco - They do appear to be steel poles. I wonder how often things like this happen with resulting tragedy. I must say I was very surprised that none of the 50 or so people involved with this whole fiasco realized there was any significant danger. After seeing this all unfold, I cant help but think that large warning plaques placed on the base of the poles (for the clueless among us) outlining minimum approach distances etc. - might save a few lives...

#124000 06/29/06 12:59 PM
Joined: Jun 2006
Posts: 613
M
Member
I had a similar experience at a light fixture in a parking lot. The fixtures were below a 250 kv transmission line and one of the lights was not working. I was commisioning the lights for turnover to the owner. I got my trusty 12 foot wooden ladder and set it up beside the pole mounted fixture and as soon as I touched the fixture i got a shock. I started cursing the guy who wired this thinking he did not bond the pole. Down at the ground I removed the access cover only to find the bonding conductor was well connected. I got my Fluke meter and tested the voltages phase to ground and phase to neutral as well as neutral to ground. 120 volts and all connections were good. So I opened the connection because I thought the ballast must have some high impedance leakage and up the ladder i go and get a shock when I touch the fixture. Now I am swearing agin but I am not sure at whom. It was at this moment I look up and think about those transmission lines. I touch a test lead of my meter against the fixture and hold the other lead in the air and get 140 volts. I raise the open lead higher and the voltage goes up. As high as I could reach I get about 170 volts. At the ground i get 50 or 60 volts. I expect it is just the field around the wires and perhaps capacitive coupling. I don't really think it was a particular hazard for a healty guy like myself but definitely uncomfortable. After this I decided I would never live under transmission lines.

#124001 06/29/06 05:59 PM
Joined: Dec 2004
Posts: 161
G
Member
As for the length of the arc, there's a difference between how far a voltage can jump across an air gap that didn't already have an arc, and how far you can pull out an arc starting from a zero gap.

I also think this is capacitive coupling, there isn't usually all that much current in the cables, cos current makes power loss (I2R) where higher volts keeps power loss down. 20'/60' * 33kV = 11kV into a very high impedance, but a lot less into a human touching it. Don't go near!

#124002 07/03/06 02:05 AM
Joined: Apr 2004
Posts: 812
Member
Quote

For effect, have someone hold a fluorescent tube under the lines.

I do that all the time under the 100-300KV (Don't quote me on that) lines behind my house, mainly to amaze my friends.

Quote
After this I decided I would never live under transmission lines.

Too late for me, there's ones behind me. There used to be houses at the ends of the drainage depression, but they were demolished when the 100-300KV transmission lines went up. I'd hate to live in an aluminum-sided trailer under a set of transmission lines.

Ian A.

[This message has been edited by Theelectrikid (edited 07-03-2006).]


Is there anyone on board who knows how to fly a plane?
#124003 07/10/06 02:26 AM
Joined: Jul 2006
Posts: 272
L
Member
Just take your volt tick and point it up and see if and glows at ya next time you are around a switchyard or trans, lines. That never gets old for me. Very good explanation of the transformer effect, "inducing a voltage onto the poles" . Kudos Rewire!


Luke Clarke
Electrical Planner for TVA.

#124004 07/10/06 04:39 PM
Joined: Feb 2005
Posts: 361
C
Member
Try it with a flores. tube [Linked Image]


~~ CELTIC ~~
...-= NJ =-...
#124005 07/11/06 06:17 PM
Joined: Jan 2006
Posts: 558
R
Member
I am gonna try it with a Fluorescent tube next time I am out walking..... I tried it with my " stupid stick" as I called it and it didnt glow until I went up and touched it to the metal of the tower!
A.D

Page 2 of 3 1 2 3

Link Copied to Clipboard
Powered by UBB.threads™ PHP Forum Software 7.7.5