ABB Relion Technical Manual page 191

1MRK 502 048-UUS A
Technical manual
tBreaker milliseconds before the rotor (power) angle reaches 0 degrees, where the
currents are at their minimum possible values. The breaker contacts will open at almost
exactly 0 degrees, as illustrated in
the breaker opening process must be initiated is estimated by solving on-line the so called
"synchronizer" differential equation. Note that if tBreaker is left on the initial (default)
value, which is zero (0), then the alternative setting TripAngle will decide when the trip
command will be given. If specified tBreaker > 0, for example tBreaker = 0.040 second,
then automatically, the TripAngle will be ignored and the second, more exact method
applied.
0.6
trip
region
0.4
3
here rotor
0.2
angle
is -90°
0 no trip
region
inside
circle
-0.2
outside the
circle is the trip
-0.4
region for
TripAngle <= 90°
-0.6 -0.4 -0.2
IEC10000114 V1 EN
Figure 81: The imaginary offset Mho circle represents loci of the impedance Z(R, X)
for which the rotor angle is 90 degrees
Figure 82 for tBreaker = 0.060 s. The point in time when
X[Ohm]
RE - Receiving End (infinite bus)
loci of Z(R, X)
no trip
region
2
no trip
rotor angle
region
= ±180°
relay
← Z - line connects
points SE & RE
SE - Sending End (generator)
0 0.2 0.4
Real part (R) of Z in Ohms →
Impedance protection
1
here
rotor angle
is +90°
R[Ohm]
this circle
←
is loci of
the rotor
angle = 90°
0.6 0.8
IEC10000114-1-en.vsd
Section 7
185