Technical data

44
1MRS751108-MUM
Protection Relay
Technical Reference Manual, General
REX 521
5.1.13. Time synchronization
The time synchronization (Configuration\Time) of the protection relay can
be given from different sources:
1. The time can always be given manually from the front panel.
2. The time synchronization can also be given externally. The master parameter for
external synchronization source selection is called Sync. source. This
parameter can have two different states:
• “Net Messages” state
• “X3.1.2 Input” state
“Net Messages” state
The parameter should be in the “Net Messages” state if the time synchronization is
taken from one of the following sources:
SPA bus
• Time synchronization is received from the SPA master device.
IEC 60870-5-103 bus
• Time synchronization is received from the IEC 60870-5-103 master device.
LON bus in the following cases:
• Time synchronization message is received from the SNVT_Timestamp input
network variable.
• Time synchronization message is received from the nv_warning/nv_clock
input network variables.
Some additional comments:
The SNVT_Timestamp network variable selector is 0x2FF5 (fixed).
The nv_warning and nv_clock selector values are 0x2FFE and 0x2FFF
respectively (also fixed).
“X3.1.2 Input” state
Synchronization is received from the digital input DI9. The input can act either as a
minute or a second synchronization input depending on the setting of the parameter
Sync.rounding. Furthermore, it is possible via the parameter
Sync.trigg.slope to set the pulse edge (positive or negative) which triggers
the synchronization.
Accuracy
When there is no external synchronization, the roaming time is better than 3 ms/min.
It is recommended that the relay is synchronized once a second in order to achieve
optimal accuracy.