Improving Reliability of IEEE-1588 in Substation Automation Based on Clock Drift Prediction

Sammanfattning: An electric substation is a node in the power grid network. It serves the purpose of transmitting and distributing electric energy from power sources to consumers. An electric substation is made of primary equipment and secondary equipment. The secondary equipment aims at protecting and controlling the primary one by sensing and analyzing various data. One pre-requisite to perform efficient protection functions is to have synchronized data provided by the various devices. The IEEE-1588 protocol is one promising way to handle the synchronized requirements of tomorrow's substation automation, however, one of the remaining issue 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 de-synchronization of the devices inside a substation or between different substations. The assignment of this master thesis project, commissioned by ABB CRC in Baden, is to investigate different drift clock prediction techniques which can handle the loss of the GPS signal, the loss of the GPS antenna receiver or the loss of the grand master device, thereby keep the substation automation synchronized without the GPS signal. Various of linear and nonlinear models of time series prediction are explored in Matlab, five main approaches based on arithmetic average, weighted average and delay coordinate embedding are eventually chosen and developed in combination with an existing open source implementation of IEEE-1588 PTPd. The five approaches' performance were judged and they have shown good results. Evaluation experiments run in our laboratory identify the most suitable technique for each type of GPS signal loss duration. On one hand, an arithmetic average based prediction technique can easily reach an accuraccy of less than 10 microseconds 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 microseconds over a period of 48 hours but at a much higher computing power cost. Keywords: IEEE-1588, Precision Time Protocol, Reliability, Substation Automation, Time Series, Prediction.