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2 Functions
Figure 2-41
Determination of
For each loop an impedance vector is also used to determine the direction of the short-
Direction
circuit. Usually similar to the distance calculation, Z
the „quality" of the measured values, different computation techniques are used. Im-
mediately after fault inception, the short-circuit voltage is disturbed by transients. The
voltage memorized prior to fault inception is therefore used in this situation. If the
steady-state short-circuit voltage (during a close-in fault) is even too small for direction
determination, an unfaulted voltage is used. This voltage is in theory quadrilateral to
the actual short-circuit voltage for both phase-earth loops as well as for phase-phase
loops (refer to Figure 2-42). This is taken into account when computing the direction
vector by means of a 90° rotation. In Table 2-11 the allocation of the measured values
to the six fault loops for the determination of the fault direction is shown.
138
Polygonal characteristic (setting values are marked by dots)
is used. However, depending on
L
7SD5 Manual
C53000-G1176-C169-1
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