ABB RELION 620 Series Technical Manual page 600

Section 6
Supervision functions
594
IL1
IL2
IL3
GUID-C5A6BB27-36F9-4652-A5E4-E3D32CFEA77B-ANSI V2 EN
Figure 303: Connection diagram for current circuit supervision with two sets of three-
phase current transformer cores (protection and measurement)
Example of incorrect connection
The currents must be measured with two independent cores, that is, the phase currents
must be measured with a different core than the reference current. A connection diagram
shows an example of a case where the phase currents and the reference currents are
measured from the same core.
IED
CCM
FAIL
I_A I_A
I_B I_B
ALARM
I_C
I_C
I_REF I_REF
BLOCK
Measurement device
1MAC504801-IB E
620 series ANSI
Technical Manual