ABB REL650 Applications Manual page 168

Section 6
Impedance protection
162
ANSI05000283 V1 EN
Figure 77: Impedance diagrams with corresponding impedances under
consideration
The outer boundary of oscillation detection characteristic in forward direction RLdOutFw
should be set with certain safety margin K
resistance R . When the exact value of the minimum load resistance is not known, the
Lmin
following approximations may be considered for lines with rated voltage 400 kV:
compared to the minimum expected load
L
1MRK 506 334-UUS A
Application manual