[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 <pjsg-timenuts at nospam.gladstonefamily.net> 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:
>>>
>>> <http://www.ko4bb.com/manuals/download.php?file=02_GPS_Timing/Simple_AC_Mains_Zero_Crossing_Detector.pdf>
>>>
>>>
>>> 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