ABB RELION RET670 Applications Manual page 486

Section 8
Impedance protection
480
IEC07000016 V1 EN-US
Figure 242: Simplified figure to derive StartAngle
ZB
³
angleStart arctan + arctan
Zload
EQUATION1977 V2 EN-US
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°.
For the TripAngle it is recommended to set this parameter to 90° to assure limited
stress for the circuit breaker.
If the centre of pole slip is within the generator block set N1Limit to 1 to get trip at first
pole slip.
If the centre of pole slip is within the network set N2Limit to 3 to get enable split of the
system before generator trip.
X
ZA
Zload
ZB
0.25
ZA
=
arctan + arctan
Zload 2
1MRK 504 163-UUS A
en07000016.vsd
0.19
0 » 0
= 7.1 + 5.4 13
2
Transformer protection RET670 2.2 ANSI
Application manual
R
(Equation 411)