calculate delays. The main disadvantage is that more inaccuracy is introduced, because the method assumes that
forw
ard and reverse delays are always the same, which may not always be correct.
When using end-to-end mode, the IED can be connected in a ring or line topology using RSTP or Self Healing
Protocol without any additional Transparent Clocks. But because the IED is a slave-only device, additional
inaccuracy is introduced. The additional error will be less than 1ms for a network of eight devices.
Figure 210: Timing error using ring or line topology
9.3.2 PTP DOMAINS
PTP traffic can be segregated into different domains using Boundary Clocks. These allow different PTP clocks to
shar
e the same netw
ork while maintaining independent synchronisation within each grouped set.
9.4 TIME SYNCHRONSIATION USING THE COMMUNICATION PROTOCOLS
All communication protocols have in-built time synchronisation mechanisms. If an external time synchronisation
mechanism such as IRIG-B, SNTP, or IEEE 1588 PTP is not used to synchr
onise the devices, the time synchronisation
mechanism within the relevant serial protocol is used. The real time is usually defined in the master station and
communicated to the relevant IEDs via one of the rear serial ports using the chosen protocol. It is also possible to
define the time locally using settings in the DATE AND TIME column.
The time synchronisation for each protocol is described in the relevant protocol description section.
Chapter 18 - Communications P14x
454 P14xEd1-TM-EN-1
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