Help identify device on power lines? 2

[pnjunction]

Hello everyone,

Can someone tell me what the device is that's highlighted in this picture?

http://www.imagehosting.com/show.php/774292_tower.JPG.html

It LOOKS like a smaller version of the insulators on the pole, but looks like it's wired up to be some sort of suppressor- as one side of it ties TO the metal pole...but they seem to be present only on that lowest wire- and why would IT be the only one with suppression?

I look at these things every time I go for a walk in the local park...and wonder. (I am fascinated by all things power-related.)

Thanks!

Johnny

 

[davidbeach]

Sorry, your image pixilates too much when trying to zoom in.

 

[BJC]

I think it's a leftover piece of an insulator. The insulator broke, they had a quick shut down to replace it. When they went to remove the old one ( or the left over piece of it), they couldn't. It could have been anything from being welded on to the condctor to not ahving the right wrench. The expedient thing to do leave it for the next time.

 

[jghrist]

It's a transmission line surge arrester. See

http://www.abb.com/Product/seitp332/c1256ccb004e670d412567e5003b0599.aspx

 

[davidbeach]

jghrist, it looks like you may be on to something, but any idea why only the bottom phase? Only on the top phase would make more sense.

 

[itsmoked]

Could've been the top phase a pole away. Add the arrester once the phase transitions so you don't have to worry about clearances on the way down from a top position.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[jghrist]

The protection is not for a direct strike to the conductor. It is to protect against backflash to the structure or downlead from the conductor. See

http://www.siriored.com/productos/TLA_Brochure.pdf

For towers with a vertical conductor configuration, conductors
arranged above each other, the resultant transient voltage
across the insulators string sets is usually higher at the bottom
phase, which presents a lower distance to the soil and lowest
coupling with the shield wire. Therefore, transmission lines
with a vertical configuration and low tower footing
impedance, only one TLA is necessary to install on the bottom
phase, but for higher impedances it might be necessary install
two and sometimes three TLA’s.

 

[DCinAC]

I believe that it is a lightning arrester, and that even though there is a grounded shield wire at the top of the pole, there is a tendency to flachover onto the lowest placed phase wire, especially if the grounding is not good in the area.

 

[JensenDrive]

Interesting. Nice to learn something new. I did not know about TLAs, and was quite fascinated by the idea that they go only on the bottom phase.

 

[electricpete]

TLA... an interesting TLA

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