I encountered an interesting presentation from NIST, ``GPS Time Backup
for Power Industry''
(https://www.naspi.org/sites/default/files/2017-03/nist_lowe_gps_time_backup_power_industry_20170322.pdf)
(supposedly from '17) on a proposed GPS fallback solution (Radio KNIT)
based on WWVB---problem is, it might rely upon the Internet (rather
than a hardened internet)... Anyway, although I'm sure that there's
much more detailed information out there regarding timing
requirements, one of the slides was interesting---``Power Grid
Application Timing Needs'':
``
---------------------------------------------------------------------------------------------------------------------------
Application
| Need
---------------------------------------------------------------------------------------------------------------------------
General Purpose
| < ±100 ms
|
Time-Stamping SCADA and Operational Data Logs
| < ±1 ms
|
Substation Monitoring e.g. phasor measurement units (PMUs) |
(IRIG-B Replacement Applications with a local PTP grandmaster )
| < ±1 μs
|
Extended distance applications
|
(fault detection, transient suppression)
| < ±1 μs
---------------------------------------------------------------------------------------------------------------------------
''
So the first two can be satisfied with WWV/WWVH and/or WWVB alone,
though I'm not sure what degree of functionality ``General Purpose''
entails... Obviously systems can theoretically incorporate graceful
degradation functionality w.r.t. T&F reference.
-Ruslan
--
Ruslan Nabioullin
Wittgenstein Laboratories
[email protected]
(508) 523-8535
50 Louise Dr.
Hollis, NH 03049
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