[RFI] Difficult power line RFI find.
Hare, Ed, W1RFI
w1rfi at arrl.org
Thu Mar 18 03:06:38 EDT 2021
No chiding, but this does represent a good example of how some RFI problems can represent important maintenance issues.
Even the neutral is not safe. If there is a problem with a transformer ground and an imbalance between the loads on each of the phases, that voltage can rise above 0V. With the problems that you described on that pole, a defective ground may well be present... or not present, as the case may be. 🙂
Ed
________________________________
From: RFI <rfi-bounces+w1rfi=arrl.org at contesting.com> on behalf of K9MA <k9ma at sdellington.us>
Sent: Thursday, March 18, 2021 1:07 AM
To: Don Kirk <wd8dsb at gmail.com>
Cc: RFI <rfi at contesting.com>
Subject: Re: [RFI] Difficult power line RFI find.
Hi Don,
Aside from the safety issue, any time you find metal on metal contact
near a power line, without secure bonding, you have a potential noise
source. One example I found was a lateral guy touching a neutral wire,
right below a single phase HV line. The electric and magnetic fields
from the HV lines can produce currents in nearby conductors, and arcing
where there is poor contact.
73,
Scott K9MA
On 3/16/2021 10:51 AM, Don Kirk wrote:
> Hi Scott and gang,
>
> Thought I would provide a status report on this case, and also provide
> a warning to others regarding something I did which I certainly don't
> condone (I'm certainly not proud of what I did and I can't stress
> safety enough). I hate to even admit what I did in public, but
> thought I should mention it as it's a good example of needing to be
> extra cautious around power poles even if you think you are safe.
>
> We were hoping the power pole (wooden pole) I found generating RFI
> last week belonged to Johnson County REMC but I could not tell since
> the pole tag number was covered up by a solar light that was likely
> installed by a homeowner. Johnson County REMC responded to our report
> and said the pole actually belonged to AES, so we discussed the
> situation with our inside contact person at AES and let them know we
> were going to get some additional data before filing a formal
> complaint but we did send them a link to a youtube video I created
> along with some pictures of the suspect pole. Here is a link to my
> video documenting the suspect pole: https://youtu.be/uo5atDTo19w
> <https://youtu.be/uo5atDTo19w>
>
> I went back to the pole on Sunday to get more data and someone had
> relocated the solar light so it was no longer covering the poles tag
> number but one of two guy wires we previously reported were wrapped
> around the pole was now partially covering part of the pole number. I
> used a wooden stick to push the guy wire slightly to the side (like a
> 1/4") to make sure I could read the pole number and the RFI suddenly
> stopped on 135 MHz which I had been monitoring by chance and the RFI
> started right back up as soon as I stopped pushing on the guy wire.
>
> I then did a closer inspection of the two guy wires that were wrapped
> around the pole and one of them (not the one I was pushing on) did
> have a connection to the neutral line high up on the pole and neither
> of the guys were connected to ground as both of their bottom ends were
> just wrapped around the pole about a foot up from earth (probably due
> to a car accident or farm implement incident, etc), and both of these
> guys were in contact with each other due to their wrapping around the
> pole on top of each other near the bottom of the pole. It appears
> that my pushing on the one guy wire caused slight tension on a
> teardrop type clip that was on the top end of the guy wire I was
> pushing and this teardrop clip (almost like a D ring) rests
> (straddles) on a through bolt assembly high on the pole which acts as
> the anchor point for the guy. Note: At least the neutral line on this
> pole is located below the hot (live) line so little chance for the guy
> lines to come in contact with the hot (live) line even though they're
> not properly secured.
>
> I then did similar tests on 24.98 MHz, 1.8 MHz, and 1710 KHz, and the
> RFI stopped each time slight pressure was applied to the guy line that
> was covering the pole tag number. I actually set up HF gear a good
> distance from the pole, had my Iphone camera recording the HF gear
> while I ran back to the pole to push slightly on the guy wire with my
> wooden stick.
>
> I then contacted our inside person at AES and told them (admitted)
> what I had done and that I was now concerned this pole was not just an
> RFI issue but also a potential electrical safety issue since the guy
> wires were not connected to earth at the bottom of the pole while one
> of them is also connected to the neutral line up on the pole and the
> guys are also not properly secured even though they are are wrapped
> around the pole (better to remove them versus have them like they
> currently are). Our AES contact person then said they had actually
> already responded to the area on Friday after our initial informal
> report to them and had identified a couple poles generating RFI in the
> area which included the one I had identified, and they had already
> issued a rush work order to fix the poles.
>
> Note: one of the two guy wires might have actually been a steel strand
> for supporting telephone wire in the past, I really have no idea.
>
> I did take what I thought was reasonable precaution using my wooden
> stick, but you can never be safe enough in my opinion and no reason to
> take the risk.
>
> Bottom line (no pun intended) is that you should not touch anything on
> a power pole even if you think you are totally safe with what you are
> doing. This is just my opinion, but I think it's sound advice which I
> know has been mentioned previously (I know hitting a pole with a
> hammer has been mentioned as a no no in the past, etc). It took me a
> day to work up the courage to post this story, and please don't
> chastise me.
>
> 73,
> Don (wd8dsb)
>
> On Wed, Mar 10, 2021 at 3:53 PM K9MA <k9ma at sdellington.us
> <mailto:k9ma at sdellington.us>> wrote:
>
> If your local utility is cooperative, they may share with you maps of
> their distribution lines.
>
> 73,
> Scott K9MA
>
>
> On 3/10/2021 11:18 AM, Don Kirk wrote:
> > Hi Eddie,
> >
> > Thanks for sharing your very similar story, and very interesting
> based on
> > the configuration of lines I was dealing with. As a matter of
> fact I was
> > using Google Earth this morning to look at the lines I was
> dealing with
> > yesterday and wish I knew more about power distribution to better
> > understand all the hardware. Nevertheless I too was dealing
> with parallel
> > running lines in the area where I found the suspect pole. One
> set of
> > lines which appear to be 3 phase run the full length of the road
> on the
> > North side of the street, and the suspect pole I located was
> also on the
> > North side of the street but it was fed by parallel running
> lines on the
> > South side of the street and I don't believe the South side of
> the street
> > lines are 3 phase. The suspect pole then fed some additional
> poles running
> > up a very long driveway to a house set way back off the road.
> The lines
> > that my antennas always pointed perpendicular to were the 3
> phase lines on
> > the North side of the street which were not physically connected
> to the
> > lines with the suspect pole as far as I can tell, and if my
> theory is
> > correct that would say the RFI I was getting induced into the 3
> phase lines
> > by the lines running on the South side of the street that were
> connected to
> > my suspect pole.
> >
> > We shall see, but boy my story sounds very familiar with yours
> as far as
> > parallel running lines with a cross over to my suspect pole
> right under
> > what I'm calling the 3 phase lines that run the full length of
> the street
> > East/West.
> >
> > Thanks,
> > Don (wd8dsb)
> >
> > On Wed, Mar 10, 2021 at 10:49 AM EDWARDS, EDDIE J
> <eedwards at oppd.com <mailto:eedwards at oppd.com>> wrote:
> >
> >> Don,
> >>
> >> Great story! Thanks for sharing.
> >>
> >> We had a very similar experience near my QTH several years ago
> affecting
> >> my home location and also another ham on about a mile north of
> me. Only
> >> difference was it was strong on low bands, and it was strongest
> on 80
> >> meters at S9+, and probably on 160meters too but neither of us
> had antennas
> >> for 160 meter back then. The other ham is a mile north of me
> and we are
> >> both in nearly a north-south line perpendicular to a 161 KV
> transmission
> >> line.
> >>
> >> Also, I should mention that I work in the utility department
> that is
> >> responsible for tracking power-line noise although it's our
> technicians
> >> that do these RFI cases regularly. I only get involve in
> problem case, or
> >> in this case when I am affected at my home shack.
> >>
> >> It appeared to be coming from the direction of the161KV line
> that runs
> >> East-West; however, when the tech was using our new HF loops we
> had the
> >> same perpendicular indications no matter which direction we
> traveled. It
> >> was staying strong for 1 to 2 miles in each direction before
> beginning to
> >> fade. Our mistake was to stay too focused on using HF freqs
> for tracking
> >> that day, but we were also initially confused by the southwest
> direction we
> >> got at the ham's QTH 1.5 miles north of the 161KV line. We
> only switched
> >> to VHF/UHF in the area to the southwest finding nothing there.
> >>
> >> We unknowingly drove past the actual source directly south of
> both ham's
> >> QTHes a few times not realizing this before ending our search
> at the end of
> >> the work day (techs are union, no OT on RFI cases).
> >>
> >> The actual source turned out to be a distribution pole on a
> 13.8KV line
> >> that ran parallel with the 161KV line for a short distance as
> it crossed
> >> over the main street perpendicular to both lines to reach a
> couple houses
> >> on that street. The RFI source was apparently causing
> induction into the
> >> 161KV line from the shorter 13.8KV line.
> >>
> >> We never had to track the source down to fix it. On my way
> home from the
> >> office that same day, as I drove toward the 161KV line while
> listening to a
> >> blank spot on my AM radio, it appeared the noise was already
> gone! As I
> >> approached the 161KV line I see a couple of our utility trucks
> working to
> >> install a new pole replacing one of the old poles on the line
> that ran
> >> parallel under the 161KV line. Since the noise never returned,
> I assume
> >> the old pole that was replaced was our source pole.
> >>
> >> Some days you just get lucky!
> >>
> >> 73, de ed -K0iL
> >>
> >> -----Original Message-----
> >> From: RFI <rfi-bounces+eedwards=oppd.com at contesting.com
> <mailto:oppd.com at contesting.com>> On Behalf Of Don
> >> Kirk
> >> Sent: Tuesday, March 9, 2021 6:27 PM
> >> To: RFI <rfi at contesting.com <mailto:rfi at contesting.com>>
> >> Subject: [RFI] Difficult power line RFI find.
> >>
> >> Just thought I should share something that was a first for me when
> >> tracking down power line RFI and man it was frustrating, and I
> have tracked
> >> down a lot of powerline RFI.
> >>
> >> I noticed some weak RFI at Dans (KB9AX) on 160 meters earlier
> this year
> >> but did not have time to track it down. Dan also complained
> about the RFI
> >> and he mentioned this week that it was not strong but had
> become very
> >> consistent. It definitely looked and sounded like powerline
> noise (120 Hz
> >> spikes observed on audio scope and SDR receiver, etc.) ---snip---
> >>
> >>
> > _______________________________________________
> > RFI mailing list
> > RFI at contesting.com <mailto:RFI at contesting.com>
> > http://lists.contesting.com/mailman/listinfo/rfi
> <http://lists.contesting.com/mailman/listinfo/rfi>
>
>
> --
> Scott K9MA
>
> k9ma at sdellington.us <mailto:k9ma at sdellington.us>
>
> _______________________________________________
> RFI mailing list
> RFI at contesting.com <mailto:RFI at contesting.com>
> http://lists.contesting.com/mailman/listinfo/rfi
> <http://lists.contesting.com/mailman/listinfo/rfi>
>
_______________________________________________
RFI mailing list
RFI at contesting.com
http://lists.contesting.com/mailman/listinfo/rfi
More information about the RFI
mailing list