Time Synchronization - ABB RED615 Technical Manual
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Section 3
Basic functions
3.5
70
Time synchronization
The IED has an internal real-time clock which can be either free-running or
synchronized from an external source. The real-time clock is used for time
stamping events, recorded data and disturbance recordings.
The IED is provided with a 48-hour capacitor back-up that enables the real-time
clock to keep time in case of an auxiliary power failure.
Setting Synch Source determines the method how the real-time clock is
synchronized. If set to "None", the clock is free-running and the settings Date and
Time can be used to set the time manually. Other setting values activate a
communication protocol that provides the time synchronization. Only one
synchronization method can be active at a time but SNTP provides time master
redundancy.
The IED supports SNTP, IRIG-B, Modbus and IEC 60870-5-103 to update the real-
time clock. IRIG-B with GPS provides the best accuracy, ±1 ms. The accuracy
using SNTP is +2...3 ms.
When Modbus TCP over TCP/IP is used, SNTP or IRIG-B time
synchronization should be used for better synchronization accuracy.
When the SNTP server IP setting is changed, the IED must be
rebooted to activate the new IP address. The SNTP server IP
settings are normally defined in the engineering phase via the SCL
file.
With the legacy protocols, the synchronization message must be
received within four minutes from the previous synchronization.
Otherwise bad synchronisation status is raised for the IED. With
SNTP, it is required that the SNTP server responds to a request
within 12 ms, otherwise the response is considered invalid.
The IED can use one of two SNTP servers, the primary or the secondary server.
The primary server is mainly in use, whereas the secondary server is used if the
primary server cannot be reached. While using the secondary SNTP server, the IED
tries to switch back to the primary server on every third SNTP request attempt. If
both the SNTP servers are offline, event time stamps have the time invalid status.
The time is requested from the SNTP server every 60 seconds.
IRIG-B time synchronization requires the IRIG-B format B004/B005 according to
the 200-04 IRIG-B standard. Older IRIG-B standards refer to these as B000/B001
with IEEE-1344 extensions. The synchronization time can be either UTC time or
1YHT530004D05 D
615 series
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