Ct Supervision (60Cts); 60Cts For 7Sr11 (60Cts-I For 7Sr12); 60Cts For 7Sr12; Figure 4-7 Logic Diagram: Ct Supervision Function (60Cts) - 7Sr11 - Siemens 7SR11 Manual

5.3

CT Supervision (60CTS)

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 for 7SR11 (60CTS-I for 7SR12)

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 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
IL1
Any 2 phases
IL2
but not all 3
IL3
Figure 4-7 Logic Diagram: CT Supervision Function (60CTS) – 7SR11
This function is retained in the 7SR12 as it provides phase discrimination, whereas the standard function provided
in the 7SR12 does not.
5.3.2

60CTS for 7SR12

Normally the presence of negative phase sequence (NPS) current in a power system is accompanied by NPS
voltage. The presence of NPS current without NPS voltage is used to indicate a current transformer failure.
The element has a setting for NPS current level 60CTS Inps and a setting for NPS voltage level 60CTS Vnps If
the negative sequence current exceeds its setting while the negative sequence voltage is below its setting for
more than 60CTS Delay then a CT failure output (60CTS Operated) is given.
Operation of the CT supervision elements can be inhibited from:
Inhibit 60CTS
©2012 Siemens Protection Devices Limited
A binary or virtual input.
&
&
A binary or virtual input.
7SR11 & 7SR12 Description Of Operation
Chapter 1 Page 67 of 76