2.5 Distance Protection
123
7SD5 Manual
C53000-G1176-C169-1
In all eight preference options, one earth fault is switched off according to the prefer-
ence scheme. The second fault can remain in the system as a simple earth fault. It can
be detected with the Earth Fault Detection in Non-earthed Systems (optional).
The 7SD5 also enables the user to switch off both fault locations of a double earth
fault. Set the double earth fault preference to All loops.
Table 2-10 lists all measured values used for the distance measuring in isolated or res-
onant-earthed systems.
Table 2-10 Evaluation of the Measuring Loops for Multi-phase Pickup in the Non-earthed
Network
Parallel Line Mea-
sured Value Correc-
tion (optional)
During earth faults on parallel lines, the impedance values calculated by means of the
loop equations are influenced by the coupling of the earth impedance of the two con-
ductor systems (Figure 2-38). This causes measuring errors in the result of the imped-
ance computation unless special measures are taken. A parallel line compensation
may therefore be activated. In this manner the earth current of the parallel line is taken
into consideration by the line equation and thereby allows for compensation of the
coupling influence. The earth current of the parallel line must be connected to the
device for this purpose. The loop equation is then modified as shown below, refer also
to Figure 2-35.
Cyclic L1 before L3 before L2 before L1 L1 (L3) CYCLIC
All loops are measured All loops
Loop pickup Evaluated loop(s) Setting of parameter 1520
L1-E, L2-E, (L1-L2)
L2-E, L3-E, (L2-L3)
L1-E, L3-E, (L3-L1)
L1-E
L3-E
L3-E
PHASE PREF.2phe = L3 (L1) ACYCLIC
L1-E, L2-E, (L1-L2)
L2-E, L3-E, (L2-L3)
L1-E, L3-E, (L3-L1)
L1-E
L3-E
L1-E
PHASE PREF.2phe = L1 (L3) ACYCLIC
L1-E, L2-E, (L1-L2)
L2-E, L3-E, (L2-L3)
L1-E, L3-E, (L3-L1)
L2-E
L2-E
L1-E
PHASE PREF.2phe = L2 (L1) ACYCLIC
L1-E, L2-E, (L1-L2)
L2-E, L3-E, (L2-L3)
L1-E, L3-E, (L3-L1)
L1-E
L2-E
L1-E
PHASE PREF.2phe = L1 (L2) ACYCLIC
L1-E, L2-E, (L1-L2)
L2-E, L3-E, (L2-L3)
L1-E, L3-E, (L3-L1)
L2-E
L3-E
L3-E
PHASE PREF.2phe = L3 (L2) ACYCLIC
L1-E, L2-E, (L1-L2)
L2-E, L3-E, (L2-L3)
L1-E, L3-E, (L3-L1)
L2-E
L2-E
L3-E
PHASE PREF.2phe = L2 (L3) ACYCLIC
L1-E, L2-E, (L1-L2)
L2-E, L3-E, (L2-L3)
L1-E, L3-E, (L3-L1)
L1-E
L2-E
L3-E
PHASE PREF.2phe = L3 (L1) CYCLIC
L1-E, L2-E, (L1-L2)
L2-E, L3-E, (L2-L3)
L1-E, L3-E, (L3-L1)
L2-E
L3-E
L1-E
PHASE PREF.2phe = L1 (L3) CYCLIC
L1-E, L2-E, (L1-L2)
L2-E, L3-E, (L2-L3)
L1-E, L3-E, (L3-L1)
L1-E, L2-E
L2-E, L3-E
L3-E; L1-E
PHASE PREF.2phe = All loops
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