6.3.4 Operation principle
The operation of protection communication supervision can be described by using
a module diagram. All the modules in the diagram are explained in the next sections.
GUID-FE089DD8-D0A0-4D3B-9287-48B11ADBAC25 V1 EN
Figure 320: Functional module diagram
Communication supervision
The protection communication is supervised because the differential calculation is
dependent on the refreshing of new analog phasor samples from the remote
terminal within the protection telegram. The new protection telegram also updates
the status of the binary signals sent by the remote terminal. The calculation of the
differential current is based on comparing the remote and local terminal measured
current samples. It is therefore essential that the protection communication
telegrams are supervised and the result of the sample latency calculation can be
used further in the differential current calculation. When the communication is able
to receive telegrams correctly from the remote end via the communication media,
the communication is assumed to be operating correctly and the COMM output is
kept active.
Communication interference detector
The communication interference detector is continuously measuring and observing
the sample latency of the protection telegrams. This value is also available as
monitored data. The function provides three output signals of which only the
corresponding one is active at a time depending on if the protection communication
supervision is in OK, WARNING or ALARM. The OK state indicates the correct
operation of the protection. The WARNING state indicates that the protection is
internally blocked due to detected interference. The WARNING state is switched to
ALARM if the interference lasts for a longer period. The protection communication
supervision can sometimes be in the WAITING state. This state indicates that the
terminal is waiting for the communication to start or restart from the remote end
terminal.
Timer
Once activated with the WARNING signal, the timer has a constant time delay value
of five seconds. If the communication failure exists after the delay, the ALARM
output is activated.
Section 6 1YHT530004D05 D
Supervision functions
590 615 series
Technical Manual
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