Operation Principle - ABB RELION REX640 Technical Manual

1MRS759142 C
6.4.4
REX640
Technical Manual
delayed protection telegrams can jeopardize the demand operate speed of the
differential protection.
When a short-term interference is detected in the protection communication channel,
the function issues a warning and the line differential functions are automatically
internally blocked. PCSITPC reacts fast for the protection communication
interferences. The blocking takes place at the latest when a communication
interruption lasting for two fundamental network periods is detected. When a severe
and long lasting interference or total interruption in the protection communication
channel is detected, an alarm is issued (after a five-second delay). The protection
communication supervision quality status is exchanged continuously online by the
local and remote PCSITPC instances. This ensures that both local and remote ends
protection blocking is issued coordinately. This further enhances the security of the
line differential protection by forcing both line end protection relays to the same
blocking state during a protection communication interference, even in cases where
the interference is detected with only one line end protection relay. There is also the
Reset delay time settings parameter available which is used for changing the required
interference-free time before releasing the line-differential protection back in
operation after a blocking due to an interference in communication.

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-341A8D44-9ADB-44F5-874A-B1EFD4B3CAE7 V1 EN
Figure 666: 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.
Section 6
Supervision functions
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