ABB Relion 670 series - Series 2.2 IEC Engineering Manual; Conditional Blocking Functionality

Boolean input and output signals may need to be inverted to fulfill the logic. ACT
supports to add the inversion logic to a binary signal.
The input signal on glue logic function blocks can only be inverted
if a glue logic function block with lower execution order in the
same cycle time is available. Similar, the output signal can only be
inverted if a glue logic function block with higher execution order
in the same cycle time is available. Up to two input signals and two
output signals can be inverted for glue logic blocks in the same
cycle time.
Even though current is injected to the IED and the IED is connected
to PCM600 in online mode, the signal value in ACT is shown as
zero.
All non-mandatory input signals have a default value that will be used when not
connected.
6.1.4 Conditional blocking functionality
GUID-37C7609A-D9CD-435F-BBEE-7518B88BEEDF v1
Functions can be blocked by loss of analog data, for example if a IEC/UCA
61850-9-2LE source malfunctions. Figure
35 shows an example where MU1
malfunctions, and all function blocks connected to that 3-phase group get blocked
as a result, this is also known as conditional blocking functionality.
1MRK 511 398-UEN C Section 6
Protection and control engineering
670 series 2.2 IEC 71
Engineering manual