R
X
Distance measuring zone
Directional line
Load encroachment
characteristic
"Phase selection"
"quadrilateral" zone
en05000673.vsd
IEC05000673 V1 EN
Figure 175: Operating characteristic in forward direction when load encroachment
is activated
Figure 107 is valid for phase-to-ground. During a three-phase fault, or load, when the
quadrilateral phase-to-phase characteristic is subject to enlargement and rotation the
operate area is transformed according to figure 108. Notice in particular what happens
with the resistive blinders of the "phase selection" "quadrilateral" zone. Due to the 30-
degree rotation, the angle of the blinder in quadrant one is now 100 degrees instead of
the original 70 degrees (if the angle setting is 70 degrees). The blinder that is nominally
located to quadrant four will at the same time tilt outwards and increase the resistive
reach around the R-axis. Consequently, it will be more or less necessary to use the load
encroachment characteristic in order to secure a margin to the load impedance.
Section 6 1MRK505222-UUS C
Impedance protection
336
Technical reference manual
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