R
X
Distance measuring zone
Directional line
Load encroachment
characteristic
"Phase selection"
"quadrilateral" zone
en05000673.vsd
IEC05000673 V1 EN
Figure 162: Operation characteristic in forward direction when load encroachment is
enabled
Figure 162 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
163. 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. 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.
1MRK 506 369-UUS - Section 8
Impedance protection
Line distance protection REL670 2.2 ANSI 337
Application manual
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