the IED connects the Access Points via a boundary clock. If PTP is “On” onredundant Access Points, the IED acts as a “Transparent Clock”.In a network there may be variety of possible masters that are connected togetherwhere the masters by selection, using the priority of PTP (also called the BestMaster Algorithm, or BMC) to determine which of them that is the best master.Priority order according to PTP1. Priority 1setting for each device, default 128, set to a lower number if this device shallbe the Grand Master.2. GM classgiven from the type of device, for instance “6” for a GPS clock, “7” for a GPSclock that has lost synch during a hold-over time, “187” for a clock that canalso be a slave.3. GM Accuracyhow accurate the time is as a enumerated value4. Offset Scaled Variancecalculated value that shows the oscillator quality5. Priority 2setting for each device, default 128, set to a lower number if this device ispreferred to be the Grand Master, if Priority 1, GM class, GM accuracy andOffsetScaledVariance are the same for all devices.6. Identity, that is the MAC-adress of the port.MAC address of the access points can be seen in LHMI underthe settings of each access point.To setup a PTP network with no obvious Grand Master, you simply connect theIEDs to one network and configure PTP to be “on” on all IEDs. On one IED, theone from which you want to set the time in the station, you set the Priority2 to 127,instead of default 128. Now, this IED has higher priority than the rest of the IEDsand will thereby act as “Grand Master”.PTP is not set from TIMESYNCGEN:1General, as SNTP is. Instead PTP is setvia a parameter of each Access Point.21.1.4 Technical data IP9658-1 v1M12331-1 v8Table 585:Time synchronization, time taggingFunction ValueTime tagging resolution, events and sampled measurement values 1 msTime tagging error with synchronization once/min (minute pulsesynchronization), events and sampled measurement values± 1.0 ms typicallyTime tagging error with SNTP synchronization, sampledmeasurement values± 1.0 ms typically1MRK 505 394-UEN A Section 21Basic IED functionsLine differential protection RED650 2.2 IEC 787Technical manual
