ABB REL650 Technical Manual page 146

Section 6
Impedance protection
140
Rotor (power) angle δ can be thought of as the angle between the two lines,
connecting point 0 in Figure 61, that is, Z(R, X) under normal load, with the points
SE and RE, respectively. These two lines are not shown in Figure 61. Normal
values of the power angle, that is, under stable, steady-state, load conditions, are
from 30 to 60 electrical degrees. It can be observed in Figure
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
Z(R, X) against time for the case from Figure 61.
4
3
normal
load
Z(R, X) unde r fa ult lies
2
on the impe dance line
or nea r (for 3-ph faults )
1
0
0
fa ult
-1
occ urrs
Unde r 3-pha s e fa ult
condition rotor a ngle
-2
of a pp. ±180 de gre e s
is m e a s ure d ...
-3
1
-4
0 200
IEC10000110 V2 EN-US
Figure 62: 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.
62 shows the rotor (power) angle and the magnitude of
|Z| in Ohms
rotor (power)
angle in rad
angle
|Z|
fault 500 ms
3
2
Z(R,X) cros s e d
the im pe da nce line , Z-line ,
1
conne cting points S E - RE
400 600 800
®
Time in millis econds
1MRK 506 382-UEN A
62 that the angle
1000 1200 1400
IEC10000110-2-en.vsd
Line distance protection REL650 2.2 IEC
Technical manual