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via Ethernet LAN.
Figure 4.6.1 shows an example of a substation automation system using Ethernet-based IEC 61850
communication.
4.7 Clock Function
The clock function (Calendar clock) is used for time-tagging for the following purposes:
• Event records
• Disturbance records
• Fault records
The calendar clock can run locally or be synchronised with the external clock such as the binary
time standard input signal, RSM clock, IEC60870-5-103 or SNTP for IEC61850 etc. or Modbus.
This can be selected by setting.
The "clock synchronise" function synchronises the relay internal clock to the binary input signal by
the following method. Since the BI signal is an "ON" or "OFF" signal which cannot express
year-month-day and hour-minute-second etc, synchronising is achieved by setting the number of
milliseconds to zero. This method will give accurate timing if the synchronising BI signal is input
every second.
Synchronisation is triggered by an "OFF" to "ON" (rising edge) transition of the BI signal. When
the trigger is detected, the millisecond value of the internal clock is checked, and if the value is
between 0~500ms then it is rounded down. If it is between 500~999ms then it is rounded up (ie the
number of seconds is incremented).
n sec
When the relays are connected with the RSM system as shown in Figure 4.4.1 and "RSM" is
Figure 4.6.1 IEC 61850 Communication Network
500ms
corrected to n sec
151
or TX
(n+1) sec
corrected to (n+1) sec
6 F 2 T 0 1 7 2
t
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