ANSI05000152_2_en.vsd
One phase-to-ground fault
67N
0
3I
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.
step1
0
I
1.2 3I
³
×
EQUATION1201 V3 EN-US
(Equation 41)
The current setting for step 1 is chosen as the largest of the above calculated residual
currents, measured by the protection.
Step 2
M15282-144 v7
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.
67N
One- or two-phase ground-fault
50/51N
0
3I
ANSI05000154_2_en.vsd
ANSI05000154 V2 EN-US
Figure 74:
Step 2, check of reach calculation
1MRK 511 401-UUS A
Section 8
Current protection
Bay control REC670 2.2 ANSI
181
Application manual
Summary of Contents for Relion REC670
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