ABB RELION 611 Series Technical Manual page 62

Section 3
Basic functions
56
The protection relay is provided with a 48 hour capacitor backup that enables the real-
time clock to keep time in case of an auxiliary power failure.
The setting Synch source determines the method to synchronize the real-time clock. If
it is 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. IEEE 1588 v2 and SNTP provide time master redundancy.
The protection relay supports SNTP, IRIG-B, IEEE 1588 v2 and Modbus to update the
real-time clock. IEEE 1588 v2 with GPS grandmaster clock provides the best
accuracy ±1 µs. The accuracy using IRIG-B and SNTP is ±1 ms.
The protection relay's 1588 time synchronization complies with the IEEE
C37.238-2011 Power Profile, interoperable with IEEE 1588 v2. According to the
power profile, the frame format used is IEEE 802.3 Ethernet frames with 88F7
Ethertype as communication service and the delay mechanism is P2P. PTP announce
mode determines the format of PTP announce frames sent by the protection relay
when acting as 1588 master, with options "Basic IEEE1588" and "Power Profile". In
the "Power Profile" mode, the TLVs required by the IEEE C37.238-2011 Power
Profile are included in announce frames.
IEEE 1588 v2 time synchronization requires a communication card
with redundancy support (COM0031).
When Modbus TCP over TCP/IP is used, SNTP or IRIG-B time
synchronization should be used for better synchronization accuracy.
With the legacy protocols, the synchronization message must be
received within four minutes from the previous synchronization.
Otherwise bad synchronization status is raised for the protection
relay. With SNTP, it is required that the SNTP server responds to a
request within 12 ms, otherwise the response is considered invalid.
The relay 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 relay 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. Supported SNTP versions are 3
and 4.
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 local
1MRS757454 D
611 series
Technical Manual