ABB REB670 Applications Manual page 394

Section 13
Logic
388
blocks to a certain level/value, or for creating certain logic. Boolean, integer, floating
point, string types of signals are available.
One FXDSIGN function block is included in all IEDs.
Example for use of GRP_OFF signal in FXDSIGN
The Restricted earth fault function REFPDIF (87N) can be used both for auto-
transformers and normal transformers.
When used for auto-transformers, information from both windings parts, together with the
neutral point current, needs to be available to the function. This means that three inputs are
needed.
REFPDIF (87N)
I3PW1CT1
I3PW2CT1
I3P
ANSI11000083_1_en.vsd
ANSI11000083 V1 EN
Figure 173: REFPDIF (87N) function inputs for autotransformer application
For normal transformers only one winding and the neutral point is available. This means
that only two inputs are used. Since all group connections are mandatory to be connected,
the third input needs to be connected to something, which is the GRP_OFF signal in
FXDSIGN function block.
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Application manual