Ct Supervision (60Cts & 60Cts-I); 60Cts-I) - 7Sr21 & 7Sr22; 60Cts) - 7Sr22; Figure 5.4.1-1 Logic Diagram: Ct Supervision Function (60Cts-I) - 7Sr21 & 7Sr22 - Siemens Argus 7SR21 Technical Manual

7SR210 & 7SR220 Description of Operation
5.4 CT Supervision (60CTS & 60CTS-I)
The relay has two methods of detecting a CT failure, depending on the relay variant.
5.4.1
(60CTS-I) – 7SR21 & 7SR22
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-I Operated) is given. If all three input currents fall below the setting, CT failure is not raised.
Operation of the CT supervision elements can be inhibited from: -
Inhibit 60CTS-I
60CTS-I Element
Enabled
Disabled
Inhibit 60CTS
Inhibit 60CTS
60CTS I
<
IL1
IL2 Any 2 phases
but not all 3
IL3
Figure 5.4.1-1
5.4.2
(60CTS) – 7SR22
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
60CTS Element
Enabled
Disabled
Inhibit 60CTS
Inhibit 60CTS
VL1 60CTS Vnps
NPS
VL2
V2
Filter
VL3
IL1 60CTS Inps
NPS
IL2
I2
Filter
IL3
Figure 5.4.2-1
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A binary input, virtual input or remote data Comms.
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Logic Diagram: CT Supervision Function (60CTS-I) – 7SR21 & 7SR22
A binary input, virtual input or remote data Comms.
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&
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Logic Diagram: CT Supervision Function (60CTS) – 7SR22
60CTS-I Delay
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60CTS Delay
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©2018 Siemens Protection Devices Limited
60CTS-I Pick-UP
60CTS-I Operated
60CTS-I Operated
60CTS Pick-Up
60CTS Operated
60CTS Operated