ABB REC670 Applications Manual page 187

1MRK 511 401-UUS A
Bay control REC670 2.2 ANSI
Application manual
3I
0
67N
One phase-to-ground fault
ANSI05000152 V2 EN-US
Figure 73: Step 1, third calculation
In this case the residual current out on the line can be larger than in the case of ground
fault on the remote busbar.
³ ×
I 1.2 3I
step1 0
EQUATION1201 V3 EN-US
The current setting for step 1 is chosen as the largest of the above calculated residual
currents, measured by the protection.
Step 2
This step has directional function and a short time delay, often about 0.4 s. Step 2 shall
securely detect all ground faults on the line, not detected by step 1.
3I
0
50/51N
67N
ANSI05000154 V2 EN-US
Figure 74: Step 2, check of reach calculation
Current protection
ANSI05000152_2_en.vsd
One- or two-phase ground-fault
ANSI05000154_2_en.vsd
Section 8
(Equation 41)
M15282-144 v7
181