ABB Relion 670 Series Technical Reference Manual page 368

Section 6
Impedance protection
362
Zone 1
E
X'
B
d
B
Pole slip
impedance
movement
IEC06000437 V2 EN
Figure 192: Movements in the impedance plain
where:
X' = transient reactance of the generator
d
X = short-circuit reactance of the step-up transformer
T
Z = impedance of the power system A
S
The detection of rotor angle is enabled when:
Zone 2
X
T
IED
jX
A
X
S
X
T
d
Apparent generator
X'
d
B
1MRK505222-UUS C
E
X
A
S
A
impedance
R
IEC06000437_2_en.vsd
Technical reference manual