Synchronization Alternatives - ABB Relion Technical Manual

1MRK 502 048-UUS A
17.2.8.3
Technical manual
time-out is set so that one message can be lost without getting a TSYNCERR, but if more
than one message is lost, a TSYNCERR is given.

Synchronization alternatives

Two main alternatives of external time synchronization are available. The
synchronization message is applied either via any of the communication ports of the IED
as a telegram message including date and time or via IRIG-B.
Synchronization via SNTP
SNTP provides a ping-pong method of synchronization. A message is sent from an IED
to an SNTP server, and the SNTP server returns the message after filling in a reception
time and a transmission time. SNTP operates via the normal Ethernet network that
connects IEDs together in an IEC 61850 network. For SNTP to operate properly, there
must be an SNTP server present, preferably in the same station. The SNTP
synchronization provides an accuracy that gives +/- 1 ms accuracy for binary inputs. The
IED itself can be set as an SNTP-time server.
SNTP provides complete time-information and can be used as both fine and coarse time
synch source. However shall SNTP normally be used as fine synch only. The only reason
to use SNTP as coarse synch is in combination with PPS as fine source. The combination
SNTP as both fine and coarse source shall not be used.
SNTP server requirements
The SNTP server to be used is connected to the local network, that is not more than 4-5
switches or routers away from the IED. The SNTP server is dedicated for its task, or at
least equipped with a real-time operating system, that is not a PC with SNTP server
software. The SNTP server should be stable, that is, either synchronized from a stable
source like GPS, or local without synchronization. Using a local SNTP server without
synchronization as primary or secondary server in a redundant configuration is not
recommended.
Synchronization via IRIG-B
IRIG-B is a protocol used only for time synchronization. A clock can provide local time
of the year in this format. The "B" in IRIG-B states that 100 bits per second are
transmitted, and the message is sent every second. After IRIG-B there numbers stating if
and how the signal is modulated and the information transmitted.
To receive IRIG-B there are one dedicated connector for the IRIG-B port. IRIG-B 00x
messages can be supplied via the galvanic interface, where x (in 00x) means a number in
the range of 1-7.
If the x in 00x is 4, 5, 6 or 7, the time message from IRIG-B contains information of the
year. If x is 0, 1, 2 or 3, the information contains only the time within the year, and year
information has to come from the tool or local HMI.
Section 17
Basic IED functions
675