2 Functions
156
7SD5 Manual
C53000-G1176-C169-1
Figure 2-53 Phasor diagram of the MHO characteristic measured values
For each distance zone an MHO characteristic can be defined by means of the param-
eter Z
r
. For each zone it may also be determined whether it operates forwards or re-
verse. In reverse direction the MHO characteristic is mirrored in the origin of the co-
ordinate system. As soon as the fault impedance of any loop is confidently measured
inside the MHO characteristic of a distance zone, the affected loop is designated as
„picked up“. The loop information is also converted to phase segregated information.
Further conditions for the pickup of a zone is that the zone may not be blocked by the
power swing blocking. Furthermore the distance protection may not be blocked or
switched off completely. Figure 2-54 shows these conditions.
The zones and phases of such a valid pickup, e.g. „Dis. Z1 L1“ for zone Z1 and phase
L1 are processed by the zone logic and the supplementary functions (e.g. teleprotec-
tion logic).
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