Clock synchronisation

[mbourhis]

some investigations

• libiec61850 can read timestamp, and generated timestamp
• libiec61850 handles the 'Timestamp' object that indicates the status of the clock synchronization ('yes', 'no', 'based on external clock signal', 'failure', ...)
• in libiec61850 there is no message to make or trigger a clock synchronization
• in libiec61850, the feature 'synchrocheck' is supported, for the control commands (but it is not a clock synchronization, it is a synchronization for triggering the command based on a voltage input)
• The IEC61850 standard indicates that the Clock synchronization is based on PTP with constant parameters ( https://en.wikipedia.org/wiki/IEC/IEEE_61850-9-3#IEEE_1588_settings) and some additional parameters (https://en.wikipedia.org/wiki/IEC/IEEE_61850-9-3#Additions_to_IEEE_Std_1588)
• PTP protocol and synchronization is supported by the Linux kernel, with a specific driver (https://www.kernel.org/doc/html/latest/driver-api/ptp.html). This driver could be install on the platforms (package available for Debian family, for instance)

  Description-en: Precision Time Protocol (PTP, IEEE1588) implementation for Linux Linuxptp is an implementation of the Precision Time Protocol (PTP) according to IEEE standard 1588 for Linux. Features include:

  • support for hardware and software time stamping via the Linux SO_TIMESTAMPING socket option.
  • support for the Linux PTP Hardware Clock (PHC) subsystem by using the clock_gettime family of calls, including the new clock_adjtimex system call
  • implementation of Boundary Clock (BC) and Ordinary Clock (OC)
  • transport over UDP/IPv4, UDP/IPv6, and raw Ethernet (Layer 2)
  • support for IEEE 802.1AS-2011 in the role of end station . PTP provides higher precision and faster synchronization than NTP even without hardware support. With hardware support, sub-microsecond accuracy can be expected. Whereas NTP is intended for WAN use, PTP is designed for LAN environments and makes use of UDP multicast.

[mbourhis]

The IEC61850 standard requires some time precision and time accuracy, but these features are managed by PTP, and not directly by IEC61850 itself:

https://www.youtube.com/watch?v=gYAdIQQkB5M https://www.youtube.com/watch?v=70DQ8Ipk9Xg