ABB REG670 - Page 262

IEC06000437_2_en.vsd
IED
B A
E
B
E
A
X’
d
X
T
X
S
Zone 1 Zone 2
jX
R
X’
d
X
T
X
S
B
A
d
Apparent generator
impedance
Pole slip
impedance
movement
IEC06000437 V2 EN
Figure 107: Movements in the impedance plain
where:
X'
d
= transient reactance of the generator
X
T
= short-circuit reactance of the step-up transformer
Z
S
= impedance of the power system A
The detection of rotor angle is enabled when:
• the minimum current exceeds 0.10 I
N
(I
N
is IBase parameter set under general
setting).
• the maximum voltage falls below 0.92 UBase
• the voltage Ucosφ (the voltage in phase with the generator current) has an angular
velocity of 0.2...8 Hz and
• the corresponding direction is not blocked.
Section 7 1MRK502052-UEN B
Impedance protection
256
Technical manual