Improving reliability of IEEE1588 in electric substation automation

The IEEE 1588 Precision Time Protocol seems to be a promising way to handle synchronization requirements of tomorrow substation automation. However, one of the remaining issues is its lack of reliability in case of the loss of the GPS signal (e.g. due to atmospheric disturbances or failure of the GPS antenna) which would lead to the desynchronization of the devices inside a substation or between different substations. To keep the devices synchronized without the GPS signal, this paper explores different drift clock prediction techniques. Three main approaches based on statistical, probabilistic and time series techniques are evaluated. On one hand, a statistical-based prediction technique can easily reach an accuracy of less than 10 μsec for a prediction duration of a couple of seconds at a minimal computing cost. On the other hand, a time series-based prediction technique can provide an accuracy of 76 μsec over a period of 48 hours but at a much higher computing power cost. Finally, we identify the most suitable technique for different type of GPS signal loss that typically occurs in the context of substation automation.