Siemens siprotec 7SA522 - Page 70

2 Functions
70
7SA522 Manual
C53000-G1176-C155-3
Table 2-3 Evaluation of the Measuring Loops for Multi-phase Pickup in the Non-earthed
Network
Parallel Line Mea-
sured Value Correc-
t i o n ( op t i o na l)
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 2-16). 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 2-13.
I
L3
· Z
L
– I
E
· Z
E
– I
EP
· Z
M
= U
L3-E
where I
EP
is the earth current of the parallel line and the ratio Z
M
/Z
L
is a constant line
parameter, resulting from the geometry of the double circuit line and the nature of the
ground below the line. These line parameters are input to the device — along with all
Loop pickup Evaluated loop(s) Setting of parameter 1220
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