Power Outage Detected by VLF System

[Jonathan]

A benefit to powerline hum (radio emissions of 60Hz and harmonics radiated by power lines) being omnipresent even in the most RF quiet locations is that you can monitor local and regional power outages very closely with a VLF receiver. A local power outage occurred around the vicinity of the VLF receiver at Spring Brook Township, PA. Here is a plot of the amplitude level of 180 Hz, a harmonic of 60 Hz, showing some power loss at ~2030UT and completely at ~2100UT:

Here you can see the hum level in greater temporal detail. What is so impressive about this power outage is how low the hum levels got. I will be pulling the audio file and listening to this period. Unfortunately, there were no whistlers or dawn chorus, but hum levels this low are quite a treat:

After the power outage ended, there were some interesting spikes, possibly due to inductive inrush, then hum levels returned to normal:

The VLF system was on a UPS during the power outage, so there definitely is benefit to keep the system up and running during local power outages, especially if the magnetosphere decides to be generous. Power grid studies are often done using VLF receivers and the benefit is that no attachment to the power lines are required. 

Jonathan

KC3EEY

[Jonathan]

Mike,

At ELF, ULF, and VLF, powerline hum (including harmonics) is omnipresent and comes from many different sources, meaning the VLF receiver detects power line emissions from the house, surrounding houses, surrounding power lines, both access, distribution, and transmission lines, and anything else supplied by mains within hundreds of miles. There is never any “one source” of powerline hum and it will always be present on a VLF receiver. In many VLF applications, power line hum is filtered so as long as it’s not at high enough levels that it causes clipping at the data acquisition input. I filter in my signal processing chain, but before I do, I continually monitor levels of 60Hz and 180 Hz

Steve,

I’ve heard of many cases where solar panel inverters create lots of noise at HF, but few have been characterized at VLF. I would imagine making these inverters VLF quiet will take much more legwork, as it always does with VLF. 

With vlfrx-tools and Spectrum Lab, an adaptive mains filter is included and is very effective. Here is a sample containing 50 Hz hum and harmonics with the adaptive mains filter in vlfrx-tools. After a few seconds, it locates the fundamental and odd/even harmonics and adaptively notches them out. It tracks them as the line frequency changes throughout the day. Once it kicks in, you can hear sferics and the VLF spectrum quite easily. It notches harmonics up to 6 kHz by default, but can notch up to 8 or 10 kHz in mains-heavy environments. Using it, you can easily hear natural radio events and amateur radio transmissions in the VLF band.

Dana,

Mains harmonics usually extend up to ~6 kHz but could extend much higher in heavy harmonic environments. Those noises you hear are not usually related to power line emission, but could be synchronous to 60 Hz because they originate from power converters synchronous to power line frequencies.

Jonathan

KC3EEY

On Tue, Dec 5, 2023 at 1:01 PM Eric Nichols <kl7...@gmail.com> wrote:

Golden Valley Electric association up here has always been very competent and eager to solve noise problems.   Probably because the head of engineering for many decades was a ham.  I believe he also trained his underlings well...the systems seems to be incredibly clean.   This may not be the case elsewhere, but I'm very grateful for our power folks up here.

73!

Eric

On 12/5/23 06:45, Dana Whitlow wrote:

David, 

As I've tried to emphasize above, all i've looked at so far is the "raspy buzz"

impulsive form of noise, which I've normally tended to regard as the most

objectionable.  However, I do recognize that the "fuzzy hum" form would

likely turn out to be more of a problem for very narrowband analyses, which

is my usual case, if a harmonic should land too close to the signal band of

interest.

Many of my experiments have involved a final measurement bandwidth of

less than 1 Hz, so I should be alert to this possibility.

Dana

On Tue, Dec 5, 2023 at 9:38 AM David G. McGaw <david....@dartmouth.edu> wrote:

Generally, transformers do not make noise.  All the electronic loads in the neighborhood on the line will create a certain amount of harmonics, though the larger loads are required to include power factor control to minimize this.  Defective insulators or branches and such across the wires do create pulse noise.

You are correct, if you can localize the source of the interference, the power company will fix it.  They do not have the capability of finding it themselves so rely on us to find and report it.  In New England, we have created a task force under ARRL to help, see <https://nediv.arrl.org/spectrum-protection-utilization/>, "Noise Identification".

73,

David N1HAC

On 12/5/23 10:34 AM, Dana Whitlow wrote:

Michael,

Since there is no electrical connection to the top end of the pipe,

basic EM theory says that the pipe is actually irrelevant to common-

mode current flows.  Whether or not the pipe provides any shielding

for E-fields is another matter, of course.  I have not looked at the

E-field issue, because even if the pipe is not grounded, the 40 ft of

unshielded wiring from the pole to the top of the pipe would by far

be the dominant radiator, and there is nothing I could do about it.

Your mention of the transformer itself being noisy is scary, because

the ultrasonic test would almost certainly fail to detect such a

problem, probably making it rather difficult to persuade the power

company to change out the transformer "on speculation".

As far as power outages are concerned, I'd love to see a county-wide

outage at night in clear WX, just so I could enjoy a dark sky for a

change.  But preferably in the summer, you understand.

Dana

On Tue, Dec 5, 2023 at 9:01 AM 'Black Michael' via HamSCI <ham...@googlegroups.com> wrote:

Make sure your metal pipe is grounded to the ground rod at your breaker panel.
You should see almost 0 Ohms between the pipe and ground connection.

It may be more likely coming in the wiring.  Do you have an oscope you can use to see what's on the wires/pipes?

The power outage is a good clue and you may be able to get the power company to come out based on that observation.
Noisy transformers are common and they are required to replace them.

Mike W9MDB








On Tuesday, December 5, 2023 at 08:55:58 AM CST, Dana Whitlow <k8yum...@gmail.com> wrote:





Michael,

I've only tried that once, during an episode of the raspy buzz form
of the problem.  I used a battery-powered AM radio in the AM BC
band so that I could use the ferrite bar antenna.

The breaker panel is located on the outside of the house, and the
incoming power comes down through a metal pipe which extends
up through the eave, with the wiring from the pole entering said
pipe through the usual arrangement used to keep rain out.

Anyway, before I turned off any breakers I moved the radio around
and concluded that the noise was manifested (at least primarily) as
a common-mode current through the metal pipe.

Next I began turning off individual breakers to see if the problem
was confined to a single circuit, but apparently it was not.  

Then, with all the individual breakers back on, I opened the master
breaker, with the same result.  The noise remained in all its glory.

I suspect a problem with the pole about 40 ft from the house, but 
did not have an ultrasonic snooper at the time.  I acquired one of
those only very recently, but have not yet put it to the acid test.

I have not yet found anybody selling giant clamp-on ferrite chokes
for  "cables" about 4 inches in diameter  :-)

Also, I have not yet investigated the fuzzy hum form of interference.

Dana




On Tue, Dec 5, 2023 at 8:25 AM 'Black Michael' via HamSCI <ham...@googlegroups.com> wrote:
> Can we assume you've tested cutting power to your house so you can determine if it's YOUR house causing any of the hum?
>
> Mike W9MDB

>
>
>
>
>
>
>
>
> On Tuesday, December 5, 2023 at 05:34:33 AM CST, Jonathan <emum...@gmail.com> wrote:
>
>
>
>
>
> A benefit to powerline hum (radio emissions of 60Hz and harmonics radiated by power lines) being omnipresent even in the most RF quiet locations is that you can monitor local and regional power outages very closely with a VLF receiver. A local power outage occurred around the vicinity of the VLF receiver at Spring Brook Township, PA. Here is a plot of the amplitude level of 180 Hz, a harmonic of 60 Hz, showing some power loss at ~2030UT and completely at ~2100UT:
>
>

> Here you can see the hum level in greater temporal detail. What is so impressive about this power outage is how low the hum levels got. I will be pulling the audio file and listening to this period. Unfortunately, there were no whistlers or dawn chorus, but hum levels this low are quite a treat:
>
>

> After the power outage ended, there were some interesting spikes, possibly due to inductive inrush, then hum levels returned to normal:
>

> The VLF system was on a UPS during the power outage, so there definitely is benefit to keep the system up and running during local power outages, especially if the magnetosphere decides to be generous. Power grid studies are often done using VLF receivers and the benefit is that no attachment to the power lines are required. 
>
> Jonathan
> KC3EEY
>
>
>

> --
> Please follow the HamSCI Community Participation Guidelines at http://hamsci.org/hamsci-community-participation-guidelines.
> ---
> You received this message because you are subscribed to the Google Groups "HamSCI" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to hamsci+un...@googlegroups.com.
> To view this discussion on the web visit https://groups.google.com/d/msgid/hamsci/CAOY0kB1bH8_cOqH0diQ7vBBaCHzuZo0h2FNRkGDkfHvA2YK23Q%40mail.gmail.com.
>
> --
> Please follow the HamSCI Community Participation Guidelines at http://hamsci.org/hamsci-community-participation-guidelines.
> ---
> You received this message because you are subscribed to the Google Groups "HamSCI" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to hamsci+un...@googlegroups.com.
> To view this discussion on the web visit https://groups.google.com/d/msgid/hamsci/2099478555.158709.1701786348336%40mail.yahoo.com.
>


--
Please follow the HamSCI Community Participation Guidelines at http://hamsci.org/hamsci-community-participation-guidelines.
---
You received this message because you are subscribed to the Google Groups "HamSCI" group.
To unsubscribe from this group and stop receiving emails from it, send an email to hamsci+un...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/hamsci/CADHrwpdx6v8A5%3Dhr3fN0wpcAR0Tq1kbLB1dpnBaeQmuw%3DLZK9Q%40mail.gmail.com.

--
Please follow the HamSCI Community Participation Guidelines at http://hamsci.org/hamsci-community-participation-guidelines.
---
You received this message because you are subscribed to the Google Groups "HamSCI" group.
To unsubscribe from this group and stop receiving emails from it, send an email to hamsci+un...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/hamsci/2096484717.169585.1701788450009%40mail.yahoo.com.

--
Please follow the HamSCI Community Participation Guidelines at http://hamsci.org/hamsci-community-participation-guidelines.
---
You received this message because you are subscribed to the Google Groups "HamSCI" group.
To unsubscribe from this group and stop receiving emails from it, send an email to hamsci+un...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/hamsci/CADHrwpeHA9SDaKf_hUY1rKt-aDeJJrh-P-ZOhcEZuLgRNr1h%2Bg%40mail.gmail.com.

--
Please follow the HamSCI Community Participation Guidelines at http://hamsci.org/hamsci-community-participation-guidelines.
---
You received this message because you are subscribed to the Google Groups "HamSCI" group.
To unsubscribe from this group and stop receiving emails from it, send an email to hamsci+un...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/hamsci/7fba57a4-23ad-48c3-b245-34e874f1c86e%40dartmouth.edu.

--
Please follow the HamSCI Community Participation Guidelines at http://hamsci.org/hamsci-community-participation-guidelines.
---
You received this message because you are subscribed to the Google Groups "HamSCI" group.
To unsubscribe from this group and stop receiving emails from it, send an email to hamsci+un...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/hamsci/CADHrwpeP7tZvK8Q1zjP_8JA_wtPwBCr5g4m%2BiKfR9UtjyLrYdg%40mail.gmail.com.

-- 
Eric P. Nichols, KL7AJ
AlasKit Educational and Scientific Resources
138 Shenandoah Drive
Fairbanks, AK 99712
(907)371-7120
www.alaskit.net
kl7...@gmail.com

--
Please follow the HamSCI Community Participation Guidelines at http://hamsci.org/hamsci-community-participation-guidelines.
---
You received this message because you are subscribed to the Google Groups "HamSCI" group.
To unsubscribe from this group and stop receiving emails from it, send an email to hamsci+un...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/hamsci/af7ffc79-f5cd-4c6c-a14b-b568ed0b12ac%40gmail.com.

[Phil Erickson]

Hi all,

  We should also emphasize that power line radiation is not just local.  In case you hadn’t seen it, power line harmonics have also been detected in near-Earth space right out to the edge of the ‘VLF bubble’ and beyond (bubble extent = the plasmasphere boundary layer, 14000 - 20000+ km altitude) essentially out to the extent of VLF transmissions and those latitudes where humans live.  This was discovered long ago by the Stanford group (Don Carpenter, Chung Park, etc.) using ground based VLF whistler observations in the Antarctic and Arctic (e.g. Roberval in Canada).  

https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/JA080i031p04249

https://link.springer.com/article/10.1007/BF00173690

  DEMETER satellite data, at 600 km altitude, has also clearly detected power line harmonics in the topside ionosphere in its data.  See this article and related ones:

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2006JA012134

  So it is truly everywhere.

73

Phil W1PJE

You received this message because you are subscribed to the Google Groups "hamsci-grape" group.
To unsubscribe from this group and stop receiving emails from it, send an email to hamsci-grape...@googlegroups.com.
To view this discussion on the web visit https://groups.google.com/d/msgid/hamsci-grape/CAOY0kB3B%2B3ei3xqrVpssGfiCXvyJK9j9s3kk4uRJR4wgrGSYNQ%40mail.gmail.com.

[Jonathan]

Phil,

I very much appreciate these resources you provided! I especially love the first paper. It also explains why I have seen what appear to be ionospheric propagation effects of powerline radiation in some of my plots, specifically at dawn when D layer absorption begins to kick in and regional/local load is low enough so those emissions don't dominate the ones that undergo waveguide propagation. I can't access the system now, but I will pull a plot when I can and post it here.

Thanks again.

Jonathan

KC3EEY 

[Jonathan]

Here on the day of the annular eclipse, powerline hum levels were low enough that the 180 Hz harmonic seemed to have exhibited ionospheric propagation. Notice the drop in amplitude at dawn. To me, this shows daytime D layer absorption as seen in other signals:

You'll also notice a slight decrease in absorption during eclipse time which is expected. 

As time went on, background hum levels increased, so this ionospheric propagation can't be seen on those days. Here is a plot of the last 60 days since the eclipse showing an increase in power levels of the 180 Hz harmonic:

Despite this, you can still see some cyclic nature from diurnal to diurnal that could indicate ionospheric propagation. The break in the data was when there was an issue with the system.

Jonathan

KC3EEY 

On Wed, Dec 6, 2023 at 7:38 AM Phil Erickson <phil.e...@gmail.com> wrote:

[Jonathan]

One of the benefits of vlfrx-tools is how powerful its signal processing tools are. I wanted to investigate the power line frequency over time to understand how it varies throughout the day. With GPS timestamped and sampled aligned data, I can see how the 180 Hz harmonic varies over time. To do so, I feed the stream into a brick wall filter centered at 180 Hz that is 2 Hz wide. Then, after downsampling, I feed it into an FM demodulator, which gives me a frequency deviation output. This frequency deviation output gives me the frequency variation that I'm looking for. I downsample some more to a rate of 1 Hz/sec to decimate and plot the data. 

Here is a plot of the 180 Hz harmonic over a span of 4 hours showing the deviations in hundreds of mHz:

The vertical scale is in mHz and the horizontal scale is in seconds, spanning 4 hours. You can see the deviation spanning ±200mHz which is really interesting! This might represent the variations in load on the local and regional grid. 

Jonathan

KC3EEY

[Jonathan]

Mike,

The amplitude level of mains hum is so loud, especially harmonics, that most of the noise is drowned out by the signal. Mains hum can account for up to 50 or 60% of the soundcard's scale on my system. There is some noise out of the FM demodulator, but that's in the uHz range or less of frequency deviation. The FM demodulator may not be utilizing any fftw functions, but I will have to check. 

Jonathan

KC3EEY

On Tue, Dec 12, 2023 at 8:39 AM 'Black Michael' via HamSCI <ham...@googlegroups.com> wrote:

Remember you aren't just measuring 180Hz -- you're also seeing the noise level in your amplitudes.  One of the weaknesses of an FFT.

If you want the 180HZ level you have to subtract the noise level.

Mike W9MDB








On Tuesday, December 12, 2023 at 05:50:45 AM CST, Jonathan <emum...@gmail.com> wrote:





One of the benefits of vlfrx-tools is how powerful its signal processing tools are. I wanted to investigate the power line frequency over time to understand how it varies throughout the day. With GPS timestamped and sampled aligned data, I can see how the 180 Hz harmonic varies over time. To do so, I feed the stream into a brick wall filter centered at 180 Hz that is 2 Hz wide. Then, after downsampling, I feed it into an FM demodulator, which gives me a frequency deviation output. This frequency deviation output gives me the frequency variation that I'm looking for. I downsample some more to a rate of 1 Hz/sec to decimate and plot the data. 

Here is a plot of the 180 Hz harmonic over a span of 4 hours showing the deviations in hundreds of mHz:

The vertical scale is in mHz and the horizontal scale is in seconds, spanning 4 hours. You can see the deviation spanning ±200mHz which is really interesting! This might represent the variations in load on the local and regional grid. 

Jonathan
KC3EEY

On Sun, Dec 10, 2023 at 9:59 PM Jonathan <emum...@gmail.com> wrote:
> Here on the day of the annular eclipse, powerline hum levels were low enough that the 180 Hz harmonic seemed to have exhibited ionospheric propagation. Notice the drop in amplitude at dawn. To me, this shows daytime D layer absorption as seen in other signals:
>

> You'll also notice a slight decrease in absorption during eclipse time which is expected. 
>
> As time went on, background hum levels increased, so this ionospheric propagation can't be seen on those days. Here is a plot of the last 60 days since the eclipse showing an increase in power levels of the 180 Hz harmonic:
>

https://groups.google.com/d/msgid/hamsci/CAOY0kB2s2eEQQURxCej-yXHZ7t4HPd6d6MoiC98uZbyDGWcmnA%40mail.gmail.com
.

--
Please follow the HamSCI Community Participation Guidelines at http://hamsci.org/hamsci-community-participation-guidelines.
---
You received this message because you are subscribed to the Google Groups "HamSCI" group.
To unsubscribe from this group and stop receiving emails from it, send an email to hamsci+un...@googlegroups.com.

To view this discussion on the web visit https://groups.google.com/d/msgid/hamsci/1182473035.186254.1702388341857%40mail.yahoo.com.

[Graham c]

This discussion has been most interesting.

You may or may not be aware that there is a study program at the University of Tennessee operated by the Power Information Technology Laboratory ( Professor Yilu Liu ). I have been hosting one of their power line monitors for more than 15 years.

web site here:  https://fnetpublic.utk.edu/index.html

more information and links to papers (etc) here:  https://powerit.utk.edu/index.html

cheers, Graham ve3gtc

To view this discussion on the web visit https://groups.google.com/d/msgid/hamsci-grape/CAOY0kB2s2eEQQURxCej-yXHZ7t4HPd6d6MoiC98uZbyDGWcmnA%40mail.gmail.com.

[Jonathan]

I was able to look at the 5 hour period during the power outage. Here is the amplitude plot of the 180 Hz harmonic:

This is the frequency deviation plot of the 180 Hz harmonic showing noise during the period in which the power was completely out. 

When the power is on, SNR is high enough so the FM detector doesn't output noise spikes of larger magnitude.

Jonathan

KC3EEY