IEC/IEEE 61850-9-3 and C37.238-2017

The 7210 SAS supports IEC/IEEE 61850-9-3 and the C37.238-2017 extension, which are profiles that allow PTP to act as a timing source in power utility networks.

The IEC/IEEE 61850-9-3 and C37.238-2017 profiles support only Ethernet encapsulation with multicast addressing. Both profiles use the peer delay mechanism instead of the delay-request and response mechanism.

When configured for IEC/IEEE 61850-9-3 or C37.238-2017, the 7210 SAS can operate as a boundary clock and supports recovery of frequency as well as time of day or phase.

Synchronous Ethernet is recommeded to be used for frequency recovery when using PTP power profile for accurate phase and time recovery.

The IEC/IEEE 61850-9-3 and C37.238-2017 profiles have the following characteristics:

• The default domain setting is 0 for IEC/IEEE 61850-9-3 and 254 for C37.238-2017; the allowed range is 0 to 255.
• One-step clock operation is supported on the 7210 SAS without the need for follow-up messages.

• Can operate timeReceiver ports that receive from a one-step or two-step timeTransmitter port.

• Only Ethernet encapsulation with multicast frames is supported with this profile.
• When Ethernet encapsulation is used, virtual local area network (VLAN) tags within Ethernet frames carrying PTP messages are not supported. When a PTP clock receives a PTP message within a frame containing a VLAN tag, it discards this frame.
• Synchronization messages, Announce messages, and peer delay messages are sent, by default, at the rate of 1 packet/s.
• By default, the priority1 and priority2 values are set to 128 when the clock-type is boundary. The priority values can be configured to be between 0 and 255.

The C37.238-2017 profile uses the IEEE_C37_238 TLV in Announce messages between the parent and slave clocks. This TLV includes the grand master clock ID and the total time inaccuracy. Each clock in the chain adds its own inaccuracy to the total time inaccuracy, which gives the ultimate slave clock an estimate of the inaccuracy over the entire path.

When acting as a boundary clock, the system receives the total time inaccuracy from the parent clock and adds its own time inaccuracy, then sends out a TLV with the updated total time inaccuracy. The user can change the default value for a boundary clock with the time-inaccuracy-override command.

See the IEC/IEEE 61850-9-3 standard and the C37.238-2017 extension for more information.