If they had old porcelain insulators and wire and just changed the line
voltage without replacing them both they that is most likely the biggest
cause of your problem. Some engineer planning the upgrade determined
that the existing insulators and wire were 'good enough' and decided to
save money by not replacing them. Most likely there are multiple
insulators that have hairline cracks which arc when they are dry but
conduct nicely when they are wet. If all the rfi guy is doing is
tightening down clamps and taking care of stray wire ends he is missing
the likely bad insulators, and while he may get some improvement will
likely miss the worst sources. Also if there are old lightning
arresters called expulsion tubes on the line those should probably be
checked and likely replaced with newer mov ones, they were mostly
designed for lower voltages and may cause problems just like old
insulators. If you are in a high contamination area, downwind from coal
burning power plants, downwind from major interstate where they salt
heavily, etc, the insulators could benefit from a good washing also.
One important thing that is often overlooked, you are actually doing the
company a service... every arc they stop is power they are saving, and
while one insulator arcing may only dissipate a few watts, hundreds of
them add up... and they are going 24/7 wasting power that adds on to
your bill in the end.
David Robbins K1TTT
e-mail: mailto:k1ttt@arrl.net
web: http://www.k1ttt.net
AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net
> -----Original Message-----
> From: rfi-bounces@contesting.com [mailto:rfi-bounces@contesting.com]
On
> Behalf Of John Pelham
> Sent: Friday, February 06, 2004 00:35
> To: rfi@contesting.com
> Subject: [RFI] My power line noise problems, revisited (Warning, this
> islong!)
>
> In 2001 I posted here about a line noise problem I was having. Well,
I'm
> still having it and I seek the group's advice as to how best to
proceed.
>
> First, a description of the problem. I truly believe it to be line
noise,
> as it sounds like a 60- or 120-Hz buzz, sometimes containing hissy-
> sounding
> audio frequencies and sometimes just a hummy buzz. Depending on
> conditions,
> it is present continuously or intermittently (kind of a sputtering
sound).
> It tends strongly to be present in the daytime and not at night, and
on
> crisp dry days, and not on rainy, humid, or even just cloudy, days.
It is
> most strongly audible on 15, 10 and 6 meters. Occasionally I can hear
it
> on
> 20M and even on 2M. When it's going good (which is lots of the time)
it's
> S9 on 6M. It's never audible on, say, the AM broadcast band.
>
> In one of my original 2001 postings I lamented how, when I contacted
my
> power company, they sent someone out who didn't seem to know or care
much.
> He said that if he couldn't hear the noise on his truck's AM radio he
> couldn't find it, but if I found suspected poles he'd be happy to
examine
> the poles and fix any found problems.
>
> To make a very long story a bit shorter, I build a DFing apparatus
> consisting of a 3-element 2M yagi and a 2M HT with an AM detector and
an S
> meter. Right away I found one source: the pole right across the
street
> from
> my house was easily DF'ed as a strong source. The power company found
> nothing when they checked the pole, but "tightened the hardware
anyway."
> It
> made a big improvement, which lasted a few weeks as I recall.
>
> I kept on complaining, and eventually found that my power company
really
> does have an RFI troubleshooting specialist. Why I wasn't put in
touch
> with
> him the first time, I don't know. I stayed home from work one crisp
> morning
> in January 2003 and met this friendly and cooperative person, and we
went
> around the neighborhood a bit together checking poles. He used three
> pieces
> of equipment: He had an HT-like radio with a rubber duckie antenna
that
> he
> said was tuned to 50 MHz. He said he used this to check on
> interference-to-TV-channel-2 type problems. He also had two
_ultrasonic_
> (high frequency audio) receivers; one with a clear plastic parabolic
> reflector that he used from street level to identify bad poles, and
one
> that
> he used right up at the wires and insulators to search out the actual
> problem spot. He said that it was easiest to find arcing by listening
> ultrasonically rather than listening to radio frequencies. And
indeed, we
> really couldn't hear anything on his 50-MHz radio with the rubber
duckie,
> but we identified a couple of arcings with the ultrasonics.
>
> It was a very educational morning for me. But, at this point I need
to
> give
> a bit more background on my problem. I've lived at this location
since
> 1983, and until 1995 or 1996 (I can't remember exactly) there was no
noise
> of any kind, ever. In 1995 or 96 my line noise problems started, and
they
> started virtually overnight like someone turned on a switch. I didn't
> complain about the problem at that time because my ham radio activity
> level
> was very low -- I had other family and job concerns that prevented me
from
> doing much hamming. I had, however, developed the habit of leaving my
6M
> radio on all the time on the SSB calling frequency, so I'd not miss
any
> openings. So it was obvious to me, even though I wasn't active, that
my
> quiescent 6M noise level had gone from S0 to S9 overnight. I just
didn't
> have any time to investigate it for several years. I did notice a big
> clue
> right at that time, though. The power company had just rebuilt the
entire
> power grid in my area. All the lines, insulators, transformers, even
some
> of the poles and pole locations, were brand new. The line noise
started
> exactly when they did this.
>
> When I told my power company line noise guy this story that morning,
he
> nodded knowingly. He said they had increased the distribution voltage
at
> that time. I don't recall what the old distribution voltage was (I
think
> he
> said either 7200 or 9600 volts), but he said the new voltage was
14400.
> He
> said that they usually get RFI complaints when they increase the
voltage,
> and wasn't surprised that that was when my problems started.
>
> What I learned that morning, in a nutshell, was that it's amazing that
any
> power can be distributed at 14400 without problems. Arcing, as
indicated
> by
> our ultrasonic testing, came and went for the most capricious of
reasons.
> For example, if a piece of debris were to strike one of those thick
> stranded
> cables that jump power from one insulator on one side of a pole to the
> other, it might get unraveled or "unstranded" slightly. I'm talking
about
> just a tiny fraction of an inch of strand separation, and just for a
short
> length, say two inches, of cable. Just these separated strands would
arc
> merrily, despite being fully connected just one inch away. The
tiniest
> hairline or speck of debris on an insulator would cause arcing. This
> stuff
> just loves to arc.
>
> Anyway, despite fixing the apparent problems at a couple of poles that
> morning (and even having my wife listen to the 6M radio in my shack
while
> we
> wiggled stuff and hearing the noise level vary), I noticed no
appreciable
> reduction in line noise in my ham shack later. It was apparent (it
> actually
> had been clear to me already) that there were _many_ different sources
of
> noise affecting my radio reception. As he parted, the power company
RFI
> guy
> said that if I would DF the noise with my tower-mounted beam and tell
him
> the direction, he would come out and try to find the source and fix
it. I
> did this many, many times over the ensuing months, and he came out
many,
> many times in response. He would usually tell me that he found this
or
> that
> problem and fixed it. Unfortunately all this activity produced at
most
> only
> a transitory reduction in noise level. Sometimes there was no
difference
> at
> all. Often I found the noise very hard to DF since there were several
> sources emitting at once from different directions.
>
> And that's where I find myself today. My line noise problem, which
has
> been
> going on since 1996, is as bad as ever. Usually there are several
sources
> all acting together to make 15 through 6M unusable no matter which
> direction
> I beam in. As always, the noise is strongest on crisp, dry, winter
days,
> and sometimes entirely absent on humid and cloudy days. My last
contact
> with the power company guy was in December 2003. I bet he's tired of
> coming
> out here only to have me report "no improvement" over and over again.
>
> So I solicit advice. Even though the power company guy seems
> knowledgeable
> and has noise-finding tools, he hasn't gotten any results in a year of
> work.
> I don't exactly know what to do at this point; at least I feel that he
is
> "on my side" regarding his willingness to work toward a solution. I
don't
> want to alienate him by suggesting he get help.
>
> Also, does anyone know if is really suitable to distribute power in a
> residential area at 14,400 volts? From my experience, this stuff will
> never
> stop arcing.
>
> I hope you enjoyed reading this as much as I did writing it! Thanks.
>
>
>
> John, W1JA
> E-mail john@radiophile.com
> Antique Radio Web Site http://www.radiophile.com
>
>
>
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