R
X
Distance measuring zone
Directional line
Load encroachment
characteristic
"Phase selection"
"quadrilateral" zone
en05000673.vsd
IEC05000673 V1 EN-US
Figure 176: Operation characteristic in forward direction when load encroachment is
enabled
Figure
is valid for phase-to-earth. 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
. 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 505 343-UEN B
Section 7
Impedance protection
287
Application manual
Summary of Contents for Relion 670 series
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