ABB Relion 670 series - Page 378

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-US
Figure 196: 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
VBase
• 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 1MRK 502 066-UUS B
Impedance protection
372
Technical manual