ABB Relion 650 Series Technical Manual page 627

1MRK 511 424-UEN B
Bay control REC650 2.2 IEC
Technical manual
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 SNTP shall normally be used as fine synch only.
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 serial communication module (SLM)
On the serial buses (both LON and SPA) two types of synchronization messages
are sent.
• Coarse message is sent every minute and comprises complete date and time,
that is, year, month, day, hours, minutes, seconds and milliseconds.
• Fine message is sent every second and comprises only seconds and
milliseconds.
The SLM module is located on the first analog digital conversion module (ADM)
Synchronization via binary input
The IED accepts minute pulses to a binary input. These minute pulses can be
generated from, for example station master clock. If the station master clock is not
synchronized from a world wide source, time will be a relative time valid for the
substation. Both positive and negative edge on the signal can be accepted. This
signal is also considered as a fine time synchronization signal.
The minute pulse is connected to any channel on any Binary Input Module in the
IED. The electrical characteristic is thereby the same as for any other binary input.
If the objective of synchronization is to achieve a relative time within the
substation and if no station master clock with minute pulse output is available, a
simple minute pulse generator can be designed and used for synchronization of the
IEDs. The minute pulse generator can be created using the logical elements and
timers available in the IED.
Section 15
Basic IED functions
M11346-33 v7
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