TIME SYNCHRONIZATION IN INDUSTRIAL PROCESS CONTROL OR AUTOMATION SYSTEMS

摘要

The present invention is concerned with improved time synchronization among the devices (2, 10, 20, 30) of an industrial process control system, and in particular of a Substation Automation system, during a temporary absence of a system reference time. Hence, disruption of time-critical protection and control functions due to re- synchronization following the temporary absence of the system reference time is avoided, and the availability of the time-critical functions configured on the devices is increased. During normal operation, a device of the system records an offset or discrepancy between the system reference time and an internal local clock of the device for a period of several hours. As soon as the system reference time breaks down, the device starts predicting the offset or drift between its local clock and the unavailable system reference time based on the recorded offset history. As a transient clock master, the device then distributes an approximated or transient system reference time, based on the device's local clock corrected for the predicted offset, to other devices of the system that in turn run time- critical protection and control functions.