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Author Topic: Stubborn RFI Problem  (Read 9427 times)
WX7G
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Posts: 6197




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« Reply #15 on: September 14, 2014, 05:55:58 AM »

There can never be a phasing problem on a U.S. power line. One interpretation of the waveform is that arcing is occurring at a 120 Hz rate but the arcing is not occurring at peak voltage; it's occurring before a peak is reached. It makes me think that a piece of floating metal is charging up and ticking over - that it's not a line-to-line arc.
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ND6P
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« Reply #16 on: September 14, 2014, 09:18:50 AM »

Here is the video that I took last night.  You can see arcing on the top of the center and right insulators, faint but the best I could get.  At the 52 second mark, a brighter arc grows on the right bottom of the center insulator and disappears.   The insulator on the far right has two arcs at the top, one on the left and one on the right.  It's interesting that all of the arcs are lined up with the wooden cross arm.  The cross arm runs north-south and the lines run east-west.  All the arcs are on the north and south side of the insulators.

This morning, there are two recurring arcs, 1.5 msec from each other every 8.3 msec and then it changed to one arc every 8.3 msec.  We are have extreme heat today so I will be watching the scope today to see if load is modulating the problem or for whatever else I can find before re-engaging the utility tomorrow.  It's 9 AM now.

http://youtu.be/EHoJ6ecurvo

Jim/ND6P
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WX7G
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« Reply #17 on: September 14, 2014, 11:47:23 AM »

Do you observe arcs on other insulators in the area?
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NK7Z
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« Reply #18 on: September 14, 2014, 12:54:12 PM »

Here is the video that I took last night.  You can see arcing on the top of the center and right insulators, faint but the best I could get.  At the 52 second mark, a brighter arc grows on the right bottom of the center insulator and disappears.   The insulator on the far right has two arcs at the top, one on the left and one on the right.  It's interesting that all of the arcs are lined up with the wooden cross arm.  The cross arm runs north-south and the lines run east-west.  All the arcs are on the north and south side of the insulators.

This morning, there are two recurring arcs, 1.5 msec from each other every 8.3 msec and then it changed to one arc every 8.3 msec.  We are have extreme heat today so I will be watching the scope today to see if load is modulating the problem or for whatever else I can find before re-engaging the utility tomorrow.  It's 9 AM now.

http://youtu.be/EHoJ6ecurvo

Jim/ND6P
Hi,

See if you can correlate the arcing with your RFI...  If the arcing is not causing your RFI, (i.e. you don't hear it when you see it), then ignore it for now...  Use two cell phones if need be, so you can hear it from your home QTH, while looking at it to be sure...  No matter what, let the power company know you believe something is arcing and let them know that you are not requesting a fix for the arcing at this time, assuming there is NO correlation, of course if there is, let them know it IS your RFI source.  Do everything you can to maintain a good relationship with your power company, short of allowing RFI to exist, which causes you problems, that they can fix.

Only worry about your strongest RFI source.  It is like peeling an onion, remove RFI one layer at a time...  I have a brief write up on the tools available, (software, and hardware), for locating and characterizing RFI at:

http://nk7z.net/rfi-now/

You will fin a large number of RFI related items on site by going to the "Site Navigation" box on the right, and clicking "RFI Mitigation".  That will list every RFI related article on the site.

Also, keep a detailed log of EVERYTHING you do, and say to anyone...  If you note times, write them down, if you talk to anyone, note the date/time, and what you talked about...  That way, later on, YOU will know what happened, and not using memory to quote what happened...  People take you much more seriously if you can tell them, you spoke to so and so, on such and such a date, about whatever...  Also, always be nice to everyone...   Once you have a log book of things done, things seen, and things noted, you can look back on it for the next time RFI hits...  Notes are probably the single best thing you can do...  Short of unplugging the source of RFI...
« Last Edit: September 14, 2014, 12:58:58 PM by NK7Z » Logged

Thanks,
Dave
For reviews and setups see: http://www.nk7z.net
ND6P
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Posts: 98




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« Reply #19 on: September 14, 2014, 01:01:15 PM »

No other arcs on the pole, except at one point prior to the tightening of hardware, I did see some arcing on one of the cutouts.  I did not see that last night.  The cutouts connect to another set of HV lines that tee off the main lines at a right angle for service down a residential block.

Jim/ND6P
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ND6P
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« Reply #20 on: September 14, 2014, 01:23:04 PM »

Dave,

Thanks for the reply and info.  I think I have the bases covered on all that you said.  I'll be visiting the pole again this evening after dark with a set of field glasses and a portable radio for one last check before relaying my latest findings to the utility tomorrow.  The utility people have been friendly, as have I.  I think getting work done beyond tightening things is the challenge here.

It seems odd to me that this is the only pole on this run that is arcing and that all three of the lines on the pole are arcing down their insulators in alignment with the cross arm.  I was hoping that someone had seen this behavior before and could shed some light.  BTW, a four-foot section of the ground wire at the bottom of the pole is missing, probably taken by vandals, if that makes any difference. The utility is aware of this as well.

I'm thinking that the utility needs to replace the insulators on this pole with a stronger type, but I'm trying to let them figure it out for themselves in case that's not the best resolution.  But if I can point them in the right direction, that would help a lot.

Jim/ND6P
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ND6P
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« Reply #21 on: September 14, 2014, 02:09:36 PM »

Here's a photo of the pole ...

https://www.flickr.com/photos/60233434@N05/15053425750/

Jim/ND6P
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ND6P
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« Reply #22 on: September 18, 2014, 04:31:53 PM »

The utility replaced the three insulators at the top of the pole today with new polymer types.  They did the same to the next pole down the line and did other maintenance on both poles as well.  I'm happy to report that the RFI has gone away.  It's still early since the work was only done this morning, but I'm pretty sure that this will hold.  I'll monitor for a few days, but I really think that they got it this time.

It's nice to have the air waves back.   Smiley

Jim/ND6P
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NK7Z
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« Reply #23 on: September 18, 2014, 04:41:31 PM »

The utility replaced the three insulators at the top of the pole today with new polymer types.  They did the same to the next pole down the line and did other maintenance on both poles as well.  I'm happy to report that the RFI has gone away.  It's still early since the work was only done this morning, but I'm pretty sure that this will hold.  I'll monitor for a few days, but I really think that they got it this time.

It's nice to have the air waves back.   Smiley

Jim/ND6P
Congratulations!!!
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Thanks,
Dave
For reviews and setups see: http://www.nk7z.net
KD6NIG
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Posts: 47




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« Reply #24 on: September 18, 2014, 07:09:32 PM »

Its good they did that for you.

Had they not done it however, I have a feeling the first good rainstorm would have probably caused them to do that.  That kind of arcing may have found a path to ground once that pole got wet.

You probably not only cured the noise, but saved them a later power outage as well.
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