ABB RES670 Applications Manual page 118

Section 7
Impedance protection
112
IEC09000225 V2 EN-US
Figure 47: 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
expected load resistance R
resistance is not known, the following approximations may be considered for lines
with a rated voltage of 400 kV:
• K = 0.9 for lines longer than 150 km
L
• K = 0.85 for lines between 80 and 150 km
L
• K = 0.8 for lines shorter than 80 km
L
ArgLd
ArgLd
(ZMRPSB)
(FDPSPDIS)
. When the exact value of the minimum load
Lmin
1MRK 511 407-UEN C
R
R
IEC09000225-2-en.vsdx
compared to the minimum
L
Phasor measurement unit RES670 2.2 IEC
Application manual