ABB REG670 - Page 270

degrees. It can be observed in Figure 112 that the angle reaches 180 degrees when the
complex impedance Z(R, X) crosses the impedance line SE – RE. It then changes the
sign, and continues from -180 degrees to 0 degrees, and so on. Figure 112 shows the
rotor (power) angle and the magnitude of Z(R, X) against time for the case from Figure
111.
0 200 400 600 800 1000 1200 1400
-4
-3
-2
-1
0
1
2
3
4
Time in millis econds
®
Impedance Z in Ohm and rotor angle in radian
®
|Z| in Ohms
angle in rad
normal
load
fault 500 ms
Z(R,X) cros s e d
the im pe da nce line , Z-line,
conne cting points SE - RE
fault
occurrs
Z(R, X) under fault lies
on the impedance line
or near (for 3-ph faults )
Unde r 3-pha s e fault
condition rotor a ngle
of a pp. ±180 de gree s
is m ea s ure d ...
rotor (power)
angle
|Z|
IEC10000110-2-en.vsd
1
2
3
1
0
IEC10000110 V2 EN
Figure 112: Rotor (power) angle and magnitude of the complex impedance Z(R,
X) against the time
In order to be able to fully understand the principles of OOSPPAM, a stable case, that
is, a case where the disturbance does not make a generator to go out-of-step, must be
shown.
Section 7 1MRK502052-UEN B
Impedance protection
264
Technical manual