R
X
Distance measuring zone
Directional line
Load encroachment
characteristic
"Phase selection"
"quadrilateral" zone
en05000673.vsd
IEC05000673 V1 EN-US
Figure 160: Operation characteristic in forward direction when load
encroachment is enabled
Figure 160 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 161. 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.
Section 8 1MRK 506 369-UEN B
Impedance protection
316 Line distance protection REL670 2.2 IEC
Application manual
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