Re: [time-nuts] Recording mains frequency/phase [WAS: No GPS satellites]

[Magnus Danielson]

Hi Bob,

On 02/27/2015 08:24 PM, Bob Camp wrote:

HI

On Feb 27, 2015, at 10:46 AM, Philip Gladstone 
 wrote:

On 2/26/15 20:39, Charles Steinmetz wrote:

ben wrote:


I'm going to have to build one of these. Assume you have some sort of
circuit that converts low-voltage AC from a transformer secondary to
a pulse train, start a timer, and count x amount of pulses?


Here is a zero-cross detector designed for this purpose:




Most mains-nuts feed the ZCD pulse to the DCD line of a PC's RS232
port and use the computer to time-stamp the crossings and append them
to a file of such time stamps.

If we all did this, then I realize that we could identify the different power 
grids. However, I wonder if there is any interesting variation *within* a grid. 
As the electricity flows vary throughout the day, it seems possible that the 
phase difference between two people on the same grid would actually change (a 
bit).

Has anybody done this experiment?


It’s done by utilities to monitor power flow and balance electric grids. The 
first data on this (grid vs GPS) date to the 1980’s. I think the
paper I recall was done by Quebec Hydro. Since then it’s become a pretty 
standard monitoring tool.


Yes. They implemented the first Phasor-Measurement Unit (PMU), it went 
into the IEEE 1344 standard, but had many issues with it and created a 
new standard in IEEE C37.118, which has since been split into IEEE 
C37.118.1 and C37.118.2 with the advent of the IEC 61850 context, where 
the data-transport is being replaced, but the measurement methods is 
maintained in C37.118.1.


For an intro, you can read this paper:
http://rubidium.dyndns.org/~magnus/papers/KTH_paper1.pdf

Cheers,
Magnus
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[time-nuts] Recording mains frequency/phase [WAS: No GPS satellites]

[Mark Sims]

When I first came across that article on theregister.com,  I thought that it 
was a rather cute idea and decided to give it a try.   I set up a couple of 
data recorders that logged AC zero crossings to an SD card (with 64 Mhz clock 
resolution).  They were set up around 8 miles apart.   I also recorded a sound 
file at each location from a sound card (92 kHz sample rate).   None of the 
recordings were time-synced and the recording time-bases were simple crystal 
oscillators.   I cut a random sections out  of the sound recordings and fed 
them into what amounts to a correlator program and ran it against the 
zero-crossing logs.  It had very few problems finding a best-fit of the sound 
snippets to the appropriate zero crossing data files.   
   
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Re: [time-nuts] Recording mains frequency/phase [WAS: No GPS satellites]

[Daniel Mendes]

I´m planning an experiment like that... I designed a board with an OCXO, 
pic microcontroller, power supply, mains interface with optocoupler, and 
SD card for data collection.. I plan to sincronize a counter running at 
10MHz between them and log events at 5 different points in my city. The 
boards also have a small Li-Ion battery and battery charger for short 
power outages. Boards are manufatured and the most expensive items have 
been bought, but not everything yet.


Daniel

On 27/02/2015 21:41, Mark Sims wrote:

Yes, it has been done...  and it has some very interesting real world uses:
http://www.theregister.co.uk/2014/07/03/tinfoil_hatters_spook_says_nsa_can_track_whistleblowers_through_power_lines/

-
If we all did this, then I realize that we could identify the different power 
grids. However, I wonder if there is any interesting variation *within* a grid. 
As the electricity flows vary throughout the day, it seems possible that the 
phase difference between two people on the same
grid would actually change (a bit).

Has anybody done this experiment?   
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[time-nuts] Recording mains frequency/phase [WAS: No GPS satellites]

[Mark Sims]

Yes, it has been done...  and it has some very interesting real world uses:
http://www.theregister.co.uk/2014/07/03/tinfoil_hatters_spook_says_nsa_can_track_whistleblowers_through_power_lines/

-
If we all did this, then I realize that we could identify the different power 
grids. However, I wonder if there is any interesting variation *within* a grid. 
As the electricity flows vary throughout the day, it seems possible that the 
phase difference between two people on the same 
grid would actually change (a bit).

Has anybody done this experiment? 
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Re: [time-nuts] Recording mains frequency/phase [WAS: No GPS satellites]

[Bob Camp]

HI
> On Feb 27, 2015, at 10:46 AM, Philip Gladstone 
>  wrote:
> 
> On 2/26/15 20:39, Charles Steinmetz wrote:
>> ben wrote:
>> 
>>> I'm going to have to build one of these. Assume you have some sort of
>>> circuit that converts low-voltage AC from a transformer secondary to
>>> a pulse train, start a timer, and count x amount of pulses?
>> 
>> Here is a zero-cross detector designed for this purpose:
>> 
>> 
>> 
>> 
>> Most mains-nuts feed the ZCD pulse to the DCD line of a PC's RS232
>> port and use the computer to time-stamp the crossings and append them
>> to a file of such time stamps.
> If we all did this, then I realize that we could identify the different power 
> grids. However, I wonder if there is any interesting variation *within* a 
> grid. As the electricity flows vary throughout the day, it seems possible 
> that the phase difference between two people on the same grid would actually 
> change (a bit).
> 
> Has anybody done this experiment?

It’s done by utilities to monitor power flow and balance electric grids. The 
first data on this (grid vs GPS) date to the 1980’s. I think the
paper I recall was done by Quebec Hydro. Since then it’s become a pretty 
standard monitoring tool. 

Bob

> 
> Philip
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Re: [time-nuts] Recording mains frequency/phase [WAS: No GPS satellites]

[Philip Gladstone]

On 2/26/15 20:39, Charles Steinmetz wrote:

ben wrote:


I'm going to have to build one of these. Assume you have some sort of
circuit that converts low-voltage AC from a transformer secondary to
a pulse train, start a timer, and count x amount of pulses?


Here is a zero-cross detector designed for this purpose:




Most mains-nuts feed the ZCD pulse to the DCD line of a PC's RS232
port and use the computer to time-stamp the crossings and append them
to a file of such time stamps.
If we all did this, then I realize that we could identify the different 
power grids. However, I wonder if there is any interesting variation 
*within* a grid. As the electricity flows vary throughout the day, it 
seems possible that the phase difference between two people on the same 
grid would actually change (a bit).


Has anybody done this experiment?

Philip
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[time-nuts] Recording mains frequency/phase [WAS: No GPS satellites]

[Charles Steinmetz]

ben wrote:

I'm going to have to build one of these.  Assume you have some sort 
of circuit that converts low-voltage AC from a transformer secondary 
to a pulse train, start a timer, and count x amount of pulses?


Here is a zero-cross detector designed for this purpose:



Most mains-nuts feed the ZCD pulse to the DCD line of a PC's RS232 
port and use the computer to time-stamp the crossings and append them 
to a file of such time stamps.


Alternatively, Tom designed the picPET Precision Event Timer to do 
this sort of timestamping:




An Ardu/berry/bone with a flash card can also be used, so you don't 
need to leave a PC running.


Best regards,

Charles



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