ABB UniGear Series, Engineering Manual

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ENGINEERING ETHERNET
1VLG5 00007 E 69
Using the Best Master Clock (BMC) algorithm devices in the network with the most accurate
time are determined, which are to be used as a reference time source (Grandmaster). Subse-
quently the participating devices synchronize themselves with this reference time source.
The BMC algorithm run continuously to quickly adjust for changes in network configuration.
IEEE 1588 networked protocol supports multiple master clock, which improves redundancy
and reliability of substation time synchronization system.
PTP clock types
– Grandmaster clock is synchronized with an external source as satellites (satellites refer-
ence clocks)
– Ordinary clock can act as either a Master or a Slave clock (protection relay). In most net-
work implementations the clocks remain in the Slave state and only become Master when
the Grandmaster fails.
– Transparent clock corrects the time information before forwarding it without synchroniz-
ing itself (Managed Ethernet switch)
The PTP Clocks can be either one-step or two-step ones; their mixing should be avoided. Two
step clock sends Sync message (contains the approximate time) and follow-up message (con-
tains more precise value of when Sync message left the clock). One step clock does not send
Follow-up message, instead the Sync message carries a precise time stamp. The One-step
mode reduces network traffic and is preferable.
System settings for the 3rd party devices
To be capable of supporting the IEEE 1588-2008 (PTPv2) version of the standard
Preferably of 1588 type according to the Power profile, either via power profile parameters or
by individually setting the parameters according to the Power Profile, with implementation in
line with the one-step mode.
Table 8: C37.238 Power Profile key parameters
Parameter Value
Path delay Peer to peer
VLAN 1 recommended
Ethertype 0x88f7
Announce period 1 s
Sync period 1 s
Pdelay period 1 s