[GTALUG] mysterious restarts

[Michael Galea]

On 06/20/16 10:21, Lennart Sorensen wrote:
> On Sat, Jun 18, 2016 at 07:58:10PM -0400, Michael Galea wrote:
>> You know of course that the grid frequency is only approximately 60.00 hz.
>> For example, it was 59.97 hz on Friday at around 5 PM.  I have heard rumors
>> that the generators spin the grid up to above 60 hz in the early morning
>> hours to compensate for the drift, but I don't know if thats a fact.  I
>> often see the grid at 60.01 hz, in the middle of the day though.
>
> Hmm, my APC SmartUPS just reports 60.0 or 60.2Hz all the time, so I
> don't think I believe it to be accurate. :)
>
> What gismo are you using to measure that?
>
The device I'm using are twin SEL751A automation relays from Schweitzer 
Engineering laboratories. Both give me pretty much the same readings, 
and I have no reason to doubt them. They are microprocessor based 
devices with good sampling rates and high accuracy. When I say 60.XX, 
its me thats truncating the digits (not the SEL)..

Someone remarked that the accuracy of 60 hz is good, and that 
over-frequencies would cancel under-frequencies. I would really doubt 
that they could do that to any great degree of accuracy. The grid is the 
largest machine on Earth, and there is more than just a single generator.

-- 
Michael Galea