ABB Relion 670 series - Page 467

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
400
80
2000
U
Z ohm
S
= = =
EQUATION1967 V1 EN (Equation 432)
Simplified, the example can be shown as a triangle, see figure 237.
ZA
ZB
Zload
R
X
en07000016.vsd
IEC07000016 V1 EN
Figure 237: Simplified figure to derive StartAngle
0 0
32 52
arctan arctan arctan + arctan = 21.8 + 33.0 55
80 80
³ = »
ZB ZA
angleStart +
Zload Zload
EQUATION1968 V2 EN
(Equation 433)
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.
1MRK 506 369-UUS - Section 8
Impedance protection
Line distance protection REL670 2.2 ANSI 461
Application manual