ABB Relion 670 Series Applications Manual page 157

1MRK 511 401-UEN Rev. K
IEC05000149 V2 EN-US
Figure 71:
The different steps can be described as follows.
Step 1
This step has directional instantaneous function. The requirement is that overreaching of the
protected line is not allowed.
3I
0
IN
IEC05000150 V4 EN-US
Figure 72: Step 1, first calculation
The residual current out on the line is calculated at a fault on the remote busbar (one- or two-
phase-to-earth fault). To assure selectivity it is required that step 1 shall not give a trip at this
fault. The requirement can be formulated according to Equation 42.
³
I 1.2 3I (remote busbar)
step1
EQUATION1199 V3 EN-US
Bay control REC670
Application manual
Connection of polarizing voltage from an open delta
×
0
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IN>
IEC05000149-2-en.vsdx
One- or two-phase earth-fault
or unsymmetric short circuit
without earth connection
IEC05000150-3-en.vsd
Section 8
Current protection
M15282-123 v6
(Equation 42)
151