ABB RELION 670 Series Applications Manual page 105

1MRK 511 364-UUS A
=
Z
CO
EQUATION1341 V1 EN-US
ANSI05000283 V1 EN-US
Figure 46: Impedance diagrams with corresponding impedances under consideration
The outer boundary of oscillation detection characteristic in forward direction
be set with certain safety margin K
When the exact value of the minimum load resistance is not known, the following approximations
may be considered for lines with rated voltage 400 kV:
Application manual
Z
(
- = +
S Z 7.43 j 33.9
SA 1
2
)
W
compared to the minimum expected load resistance R
L
Section 7
Impedance protection
(Equation 22)
RLdOutFw should
.
Lmin
99