ABB RET670 Applications Manual page 264

Section 3
IED application
258
X1
8
Zm
Resistive reach with load encroachment characteristic
The procedure for calculating the settings for the load encroachment consist basically
to define the load angle LdAngle, the blinder RLdFwd in forward direction and blinder
RLdRev in reverse direction, as shown in figure 111.
LdAngle
LdAngle
RLdRev
ANSI05000226 V1 EN
Figure 111: Load encroachment characteristic
The load angle LdAngle is the same in forward and reverse direction, so it could be
suitable to begin to calculate the setting for that parameter. Set the parameter to the
maximum possible load angle at maximum active load. A value bigger than 20° must
be used.
The blinder in forward direction, RLdFwd, can be calculated according to equation 176.
V
2
min
= ×
RLdFwd 0.8
P exp max
where:
P exp max is the maximum exporting active power
V min
is the minimum voltage for which the Pexp max occurs
0.8 is a security factor to ensure that the setting of
minimal resistive load.
X
RLdFwd
LdAngle
LdAngle
en05000226_ansi.vsd
RLdFwd can be lesser than the calculated
1MRK504116-UUS C
R
Application manual