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Author Topic: Powerline RFFI in dew  (Read 3009 times)
WX2S
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Posts: 759




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« on: August 19, 2014, 09:55:50 AM »

Hi, all,

I've got a stubborn powerline RFI problem that shows up in heavy dew, but not rain. I've DFed it to a pole near my house with a transformer. The power company has trimmed the trees and vines around the source, so I don't think the cause is vegetation. The transformer looks to be fairly new and in good shape.

What else could cause a transformer or 6kv line to spark in dew?

Thanks and 73,
- Steve WX2S
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73, - Steve WX2S.
I subscribe to the DX Code of Conduct. http://dx-code.org/
AA4PB
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Posts: 13032




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« Reply #1 on: August 19, 2014, 10:53:03 AM »

It's often the insulators and/or the retaining pins that hold them in place. You need to get the power company to come out and replace the insulators. The biggest problem that I've run into is that often when you "quiet down" one pole you start to hear the noise being generated by another.
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WX2S
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« Reply #2 on: August 19, 2014, 11:57:37 AM »

Found out that power lines can be power-washed with deionized water too. Don't know whether PSE&G has the equipment to do this or not.

For example:

www.haverfield.com/innovated-services/energized-insulator-washing/

I'm going to have to go out there in the dark with a pair of binoculars and see if I can see the arc.

- WX2S
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73, - Steve WX2S.
I subscribe to the DX Code of Conduct. http://dx-code.org/
AA4PB
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« Reply #3 on: August 19, 2014, 12:18:22 PM »

The ARRL has a good book for sale: "AC Power Interference Handbook" by Marv Loftness, KB7KK. It explains that the arcing can be in a place that is hidden from view from the ground.
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WX7G
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« Reply #4 on: August 19, 2014, 03:25:06 PM »

Found out that power lines can be power-washed with deionized water too. Don't know whether PSE&G has the equipment to do this or not.

- WX2S


No need for deionized water as plain old water out of water hydrants is used. The nozzle design is such that the water is sprayed as isolated drops having enough spacing to not arc.

http://www.yashmunengineers.com/services/hlwhlm.php
« Last Edit: August 19, 2014, 03:27:37 PM by WX7G » Logged
AA4HA
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Posts: 1640




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« Reply #5 on: August 19, 2014, 03:59:03 PM »

This may be stating the obvious but you do not want to try to wash down a pole insulator with your garden hose. The result is called "dead".

Distribution system insulators can get dirty and leak. It is just as likely that it is an old insulator and it is "crazed" across the ceramic or has carbon tracking on spots. The best solution is for the utility to come out and replace the insulator.

You may find that at night, if it is really dark outside, you may actually see the blue glow from the corona across the insulator.

One of the things that you can say that might spur them into action is if you report that sometimes when it is really damp outside that you see a flash like a miniature lightning spark on the pole. Do not be specific about what insulator (since you really do not know). Usually that will get them to send a truck out there to check it out. If they get in the right mood they will just replace all of the insulators on that pole.

You may see a different looking insulator with a wire to ground, usually it looks taller than a normal pole insulator and can almost act like a standoff post for the wire going to the primary side of the transformer. That is a lightning protector; they are just super-sized versions of MOV's (metal oxide varistors) with a bunch of coin sized MOV's in series inside of the insulator. I have seen some of these lightning protectors that are the size of a 2 liter soda bottle and they are filled with hockey-puck sized MOV's. At one substation one of those exploded and embedded pieces of insulator into the walls of the station house (little building in a substation).
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Ms. Tisha Hayes, AA4HA
Lookout Mountain, Alabama
KI6LZ
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« Reply #6 on: August 19, 2014, 04:11:36 PM »

LOL at separating water droplets.
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W5WSS
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Posts: 1783




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« Reply #7 on: August 19, 2014, 04:26:35 PM »

KI6LZ but a steady stream can conceivably make a circuit, and the rubber hose is conceivably not enough to insulate the user through whatever footwear to ground.

I think that is possible and even probable under certain circumstances.

I agree with AA4AH let them fix it.

73
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AA4PB
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« Reply #8 on: August 19, 2014, 04:56:33 PM »

If you read the info on the link provided you'll see that it is a company that uses very specialized equipment and can provide the cleaning services to the power companies. They are not talking about an untrained consumer using a water hose to clean insulators on the pole.

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