Overall High Impedance Differential Protection (87/50-N); Figure 3-2 Logic Diagram: Differential Protection - Siemens 7SR23 DAD Manual

3.1

Overall High Impedance Differential Protection (87/50-n)

Two 87/50 high impedance elements are provided for each current input (87/50-1 and 87/50-2).
The fundamental frequency current is measured by the phase CT inputs.
87/50-n Setting defines the current required to operate the differential element. 87/50-n outputs are available for
any phase or for each individual phase.
When 87/50-n Trip Check Logic is Enabled outputs are available when any two phases operate (i.e. 87/50-n
phase-phase check).
Operation of the differential elements can be inhibited from:
Inhibit 87/50-n
CT50 CT Supervision Action: Inhibit
Zone Switchout
User Inhibit
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A binary or virtual input.
Operation of the CT Supervision elements
Control Menu, data comms or input matrix selection.
Reylogic (graphical logic)
Figure 3-2 Logic Diagram: Differential Protection
Chapter 1) 7SR23 DAD Description Of Operation
Chapter 1 Page 17 of 36