6.4.3
Functionality
The protection communication supervision function PCS monitors the protection
communication channel. PCS blocks the line differential protection functions when
interference in the protection communication channel is detected. The blocking takes
place automatically for the 87L and BST functions which are dependent on the continuous
availability of the protection communication channel.
The protection communication channel is continuously monitored by PCS. The function
detects missing or delayed protection telegrams. Protection telegrams are used for
transferring the sampled analog and other protection related data. Missing or 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. PCS 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 PCS 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.
6.4.4
Operation principle
The operation of PCS can be described by using a module diagram. All the modules in the
diagram are explained in the next sections.
Section 6
1MAC059074-MB A
Supervision functions
862
615 series ANSI
Technical Manual
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