4.2.6 Technical dataTable 14:Self supervision with internal event listData ValueRecording manner Continuous, event controlledList size 1000 events, first in-first out4.3 Time synchronization4.3.1 IntroductionThe time synchronization source selector is used to select a common source ofabsolute time for the IED when it is a part of a protection system. This makes itpossible to compare event- and disturbance data between all IEDs in a stationautomation system possible.Micro SCADA OPC server should not be used as a timesynchronization source.4.3.2 Principle of operation4.3.2.1 General conceptsTime definitionsThe error of a clock is the difference between the actual time of the clock, and thetime the clock is intended to have. The rate accuracy of a clock is normally calledthe clock accuracy and means how much the error increases, that is how much theclock gains or loses time. A disciplined (trained) clock knows its own faults andtries to compensate for them.Design of the time system (clock synchronization)The time system is based on a software clock, which can be adjusted from externaltime sources and a hardware clock. The protection and control modules will betimed from a hardware clock, which runs independently from the software clock.See figure 28.1MRK 505 208-UEN B Section 4Basic IED functions63Technical reference manual
