ABB RELION REX640, Техническое руководство, Страница: 1328 / 1960

6.4.4 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.
Figure 755: 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 continuously measures and observes 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. These output signals are set to the
FALSE state until the first telegram is received over the communication link and
supervision is started. 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.
Supervision functions 1MRS759142 F
1328 REX640
Technical Manual