GPS Error - significant timing anomaly

The electric power industry is increasingly using technology which is dependent on GPS based time synchronization. Phasor Measurement Units (PMUs) and IEC 61850 Merging Units (Mus) require time synchronization accuracy of 1 microsecond.

That is why reports about errors in the timing signal reported at the end of January 2016 need to be considered from the point of view of the impact of these errors on protection and control IEDs.
A specific anomaly in the timing signals was detected on 26 January 2016 where a deviation of 13.7 microseconds was detected when compared to the hydrogen maser atomic clock in Kirkkonummi, Finland.

The analysis determined that this fault was apparently the result of a failure on an aging (1990) satellite SVN 23 of the type II-IIA, starting on January 26 at 12:49 Mountain Time.This change occurred when the satellite was removed from the constellation of GPS satellites orbiting Earth.

While the core navigation systems were working normally, the coordinated universal time timing signal was off by 13 microseconds which exceeded the design specifications.

Operator procedures were modified to prevent a repeat of the GPS timing anomaly, until the ground system software has been corrected. An operational review will also be conducted into procedures and impacts on users. 
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