ABB RELION 670 Series Technical Manual page 1256

Section 21
Basic IED functions
21.1.3.3 Synchronization alternatives
Four main alternatives of external synchronization sources are available. The synchronization
message is applied:
• via any of the communication ports of the IED as a telegram message including date and time
• as a minute pulse connected to a binary input
• via GPS
• via IRIG-B or PPS
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. 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 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 Numeric processing module (NUM).
Synchronization via Built-in-GPS
The built-in GPS clock modules receive and decode time information from the global positioning
system. The modules are located on the GPS time synchronization Module (GTM).
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.
1250
1MRK 502 066-UUS B
M11346-3 v7
M11346-33 v6
GUID-588FCD12-C494-445E-8488-8287B34EFD9A v4
M11346-50 v6
M11346-39 v5
M11346-42 v6
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