Protection: Restricted Earth Fault (87Ref); Figure 3-4 Logic Diagram: Restricted Earth Fault Protection - Siemens 7SR23 DAD Manual

3.3

Protection: Restricted Earth Fault (87REF)

Two 87REF elements are provided (87REF-1 and 87REF-2). 87REF-1 earth current is measured by the earth
current input, 87REF-2 current is measured by the I
the fundamental frequency (50 or 60Hz).
Two restricted earth fault elements are provided.
87REF-n Setting defines the current required to operate the REF element. The output of 87REF-n Delay can be
mapped to relay outputs.
Operation of the REF-n element can be inhibited from:
Inhibit 87REF-n
User Inhibit
Figure 3-4
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current input. These elements utilise RMS current values of
B
A binary or virtual input.
Reylogic (graphical logic)
Logic Diagram: Restricted Earth Fault Protection
Chapter 1) 7SR23 DAD Description Of Operation
Chapter 1 Page 19 of 36