Siemens siprotec 7SD5 User Manual page 152

2 Functions
Figure 2-49
Properties of the As the quadrature or memorized voltage (without load transfer) equals the corre-
MHO Characteristic sponding generator voltage E and does not change after fault inception (refer also to
Figure 2-50), the lower zenith is shifted in the impedance diagram by the polarizing
quantity k·Z
fault location F
the source impedance is in the reverse direction. All fault locations, right up to the
device mounting location (current transformers) are clearly inside the MHO character-
istic (Figure 2-50b). If the current is reversed, the zenith of the circle diameter changes
abruptly (Figure 2-50c). A reversed current I
(current transformer) which is determined by the source impedance Z
zenith Z
conjunction with load transport via the line, the zenith vector may additionally be
rotated by the load angle.
152
Polarized MHO characteristic
= k·E /I . The upper zenith is still defined by the setting value Z
V1 1 1
(Figure 2-50a) the short-circuit location is in the forward direction and
1
remains unchanged; it now is the lower boundary of the circle diameter. In
r
now flows via the measuring location
2
C53000-G1176-C169-1
. For the
r
+ Z . The
S2 L
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