ABB REL650 Applications Manual page 134

Section 6
Impedance protection
128
X
Zm
Load impedance area in
ANSI05000495 V2 EN
Figure 61: Load encroachment phenomena and shaped load encroachment
characteristic defined in Phase selection with load encroachment
function FDPSPDIS (21)
jX
Load
Load
IEC06000403 V1 EN
Figure 62: Load encroachment phenomena and shaped load encroachment
characteristic
The load encroachment algorithm will increase the possibility to detect high fault
resistances, especially for phase to ground faults at remote line end. For example, in
quadrilateral characteristic, a given setting of the load angle LdAngle for phase selection
with load encroachment, the resistive blinder for the zone measurement can be expanded
according to the figure 61
unwanted operation due to load encroachment. This is valid in both directions. Again, for
example in mho characteristic, for a given setting of the load angle LdAngle (see
figure 63), the zone reach can be expanded according to the diagram on the right in
figure 62 given higher fault resistance coverage without risk for unwanted operation due
forward direction
LdAngle
R
LdAngle
Load
Load
R
Load
Load
given higher fault resistance coverage without risk for
1MRK 506 334-UUS A
Zm
ZL
LdAngle
LdAngle
RLdFwd
RldRev
ANSI05000495_2_en.vsd
jX
Load
Load
No
operation
en06000403.vsd
Application manual
R
R