ABB RET670 Applications Manual page 389

1MRK504116-UUS C
Application manual
The warning angle (StartAngle) should be chosen not to cross into normal operating
area. The maximum line power is assumed to be 2000 MVA. This corresponds to
apparent impedance:
2 2
U 400
= = =
Z 80 ohm
S 2000
EQUATION1967 V1 EN
Simplified, the example can be shown as a triangle, see figure 171.
IEC07000016 V1 EN
Figure 171: Simplified figure to derive StartAngle
ZB
³
angleStart arctan + arctan
Zload
EQUATION1968 V2 EN
In case of minor damped oscillations at normal operation we do not want the protection
to start. Therefore we set the start angle with large margin.
Set StartAngle to 110°
X
ZA
Zload
ZB
ZA 32 52
=
arctan + arctan
Zload 80 80
IED application
en07000016.vsd
»
0 0
= 21.8 + 33.0 55
Section 3
(Equation 323)
R
(Equation 324)
383