Resistive Reach With Load Encroachment Characteristic - ABB REL670 2.2 IEC Applications Manual

Section 8
Impedance protection
8.2.3.2
208

Resistive reach with load encroachment characteristic

The procedure for calculating the settings for the load encroachment consist
basically to define the load angle ArgLd, the blinder RLdFw in forward direction
and blinder RLdRv in reverse direction, as shown in figure 106.
ArgLd
ArgLd
RLdRv
IEC09000050 V1 EN-US
Figure 106: Load encroachment characteristic
The load angle ArgLd 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, RLdFw, can be calculated according to
equation 100.
2
U min
= ×
RLdFw 0.8
P exp max
where:
P exp max is the maximum exporting active power
U 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.
The resistive boundary RLdRv for load encroachment characteristic in reverse
direction can be calculated in the same way as RLdFw, but use maximum
importing power that might occur instead of maximum exporting power and the
relevant Umin voltage for this condition.
X
RLdFw
ArgLd
R
ArgLd
IEC09000050-1-en.vsd
1MRK 506 369-UEN B
RLdFw can be lesser than the calculated
Line distance protection REL670 2.2 IEC
Application manual
M13142-312 v4