ABB RELION REX640 Technical Manual page 118

Section 3
Basic functions
112
The protection relay supports SNTP, IRIG-B, IEEE 1588 v2, DNP3, Modbus, IEC
60870-5-101/104 and IEC 60870-5-103 to update the real-time clock. IEEE 1588 v2
with the GPS grandmaster clock provides the accuracy of ±1 µs. The accuracy is ±1
µs with IRIG-B and ±1 ms with SNTP.
When using line differential communication between the protection relays, the time
synchronization messages can be received from the other line end protection relay
within the protection telegrams. The protection relay begins to synchronize its real-
time clock with the remote end protection relay's time if the "Line differential" time
synchronization source is selected. This does not affect the protection synchronization
used in the line differential protection or the selection of the remote end protection
relay's time synchronization method.
GNRLLTMS supervision functionality depends on the synchronization source. This
means that the GNRLLTMS supervision signal values and their combinations have
different meanings depending on the used synchronization source.
SNTP
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 the primary
server becomes available, the warning is cleared. 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.
IEEE 1588v2
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 the 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 a 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.
Time synchronization with IEEE 1588 v2 can create many possible scenarios since it
is a dynamic synchronization method whereby the current master is determined with
BMC algorithm. GNRLLTMS outputs are reflective of this status. When IEEE 1588
v2 is used as a time synchronization source, the device stores the grandmasters in
priority order according to the BMC algorithm. When the grandmaster clock is lost,
alarm and warning are activated based on the stored grandmasters' list. The alarm is
activated when there are no clocks available which have equivalent capabilities as
primary or secondary grandmaster clocks. The warning is activated when primary
grandmaster clock is not available. The grandmaster list can be cleared using the Clear
clock list setting, for example, if the grandmaster clocks need to be replaced. The
setting affects only the alarm and warning states.
1MRS759142 C
REX640
Technical Manual