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3 zone impedance protection (Z(n)RW)
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The limitation in the reactive reach is a straight line, parallel with the R-axis. The lim-
itation in the resistive reach is two straight parallel lines with a small incline (9°) to-
wards the X-axis crossing the R-axis at +/-RF.The setting value of the resistive and re-
active reach determines whether the resistive directional line in the second quadrant in-
fluences the characteristic or not.
The directional line forms an angle of 25° towards the X-axis in the second quadrant.
In the fourth quadrant the angle (ArgDir) can be set to 15°, 30° or 45° towards the R-
axis in order to adapt the setting to series compensated lines. ArgDir is valid for all
zones.
An extra directional line (ArgLd) can be placed in the first quadrant for zones two and
three to reduce load encroachment problems. The angle for this can be set to 15°, 30°
or 45° towards the R-axis. If ArgLd is set the directional line in the fourth quadrant ap-
plies only zone 1.
The direction for each zone can be programmed. In figure 30, a typical example of char-
acteristics for non-directional, reverse and forward directed impedance measuring
zones are shown. The set value of a reach in the resistive direction determines whether
the directional line in the second quadrant meets the reactive or the resistive blinder.
The values for the reach in the reactive and resistive direction for a particular zone are
the same for forward and reverse impedance measuring elements and for the non-direc-
tional mode of operation.
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