Siemens 7SR18 Solkor - CT Supervision (60 CTS-I & CTS); 60 Cts-I; Figure 5.3.1-1 Logic Diagram: CT Supervision Function (60 CTS-I)

7SR18 Description Of Operation
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5.3 CT Supervision (60CTS-I & CTS)
The relay has two methods of detecting a CT failure, depending on the relay model. CT Supervision is only
available in relays with four current inputs.
5.3.1 60CTS-I
The current from each of the Phase Current Transformers is monitored. If one or two of the three input currents
falls below the CT supervision current setting CTS-I for more than 60CTS-I Delay then a CT failure output
(60CTS Operated) is given. If all three input currents fall below the setting, CT failure is not raised.
An output is also given to indicate the faulted phase, 60CTS-I PhA, 60CTS-I PhB, and 60CTS-I PhC
Operation of the CT supervision elements can be inhibited from:
Inhibit 60CTS-I A binary or virtual input.
60CTS-I Delay
IL1
IL2
IL3
60CTS I-I
<
Any 2 phases
but not all 3
&
Inhibit 60CTS-I
60CTS-I Element
Enabled
Disabled
&
60CTS-I Operated
Figure 5.3.1-1 Logic Diagram: CT Supervision Function (60CTS-I)