[time-nuts] Re: Is there an application for time-stamping with absolute time?

[Magnus Danielson]

Hi,

On 2024-07-12 23:11, Joe Fitzgerald via time-nuts wrote:
>
> On 7/12/2024 4:03 PM, Tom Van Baak via time-nuts wrote:
>> Â I'm told power companies used these products to locate faults along 
>> transmission lines, a clever use of GPS.
>
>
> It is curious to talk about standardized time stamps for power company 
> telemetry.    I spend my days managing the flow of data between 
> sources and sinks using various electrical grid protocols, and there 
> are at least 37 different standard ways of specifying the time of a 
> measurement - and they are not always definitive. For example the DNP3 
> standard says something to the effect of "Leap seconds,  yes we have 
> heard of them.    We are not sure what to do about them so it is up to 
> end users to figure it out on their own"

This being said, I would like to point out that the IRIG-B profile as it 
exist in the IEEE C37.118.1 spec is actually pretty darn good. There are 
times when the power-people get it right. I've also seen power-people do 
other stuff which isn't good and certainly not careing about 
leap-seconds. The NASPI TSTF report of March 2017 have a few fun 
illustrations.

Leap seconds create a little fun mess when not dealt properly with when 
doing phasor measurements using PMUs. Since the power-grid isn't perfect 
50 Hz or 60 Hz, the reference phase can jump and the difference between 
phase before or after that jump is caused by the frequency error. This 
can cause false warnings down the line, unless you consider the 
possibility of leap-second error and you can readily detect it, because 
you know the frequency from the second before, as a by-product of the 
measurements. The PMUs has a reference phase which should actually 
follow TAI and then timestamps that should follow UTC, but that's not 
quite how the standard articulate it.

Cheers,
Magnus