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.
I3PW1CT1
I3PW2CT1
I3P
REFPDIF (87N)
ANSI11000083_1_en.vsd
ANSI11000083 V1 EN
Figure 389: 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.
I3PW1CT1
I3PW2CT1
I3P
REFPDIF (87N)
ANSI11000084_1_en.vsd
GRP_OFF
FXDSIGN
ANSI11000084 V1 EN
Figure 390: REFPDIF (87N) function inputs for normal transformer application
1MRK 506 369-UUS - Section 17
Logic
Line distance protection REL670 2.2 ANSI 803
Application manual
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