0 200 400 600 800 1000 1200
-5
0
5
10
15
20
25
30
35
Current in kA, trip command to CB, rotor angle in rad
→
Time in milliseconds
→
pos. seq. current in kA
trip command to CB
rotor angle in radian
fault
occurs
←
normal load current
←
min. current
very high currents due
to out-of-step condition
←
after 1st
pole slip
←
2nd
←
rotor angle
angle towards 0°
current decreases
fault cleared
→
current increases under
fault conditions
→ ←
tBreaker = 60 ms
trip command
→
issued here
IEC10000115-1-en.vsd
IEC10000115 V1 EN-US
Figure 206: Trip initiation when the break-time of the circuit breaker is known
7.11.7.5 Design
GUID-1615F014-3529-45D0-813B-153754DED1C7 v3
At every execution of the function the following is calculated: active power P, reactive power Q,
rotor angle ROTORANG, quantity UCOSPHI, the positive-sequence current CURRENT and voltage
VOLTAGE. All other quantities, that can as well be read as outputs, are only calculated if the Z(R, X)
enters the limit of reach zone, which is a circle in the complex (R – X) plane. When the complex
impedance Z(R, X) enters the limit-of-reach region, the algorithm:
• determines in which direction the impedance Z moves, that is, the direction the lens is
traversed
• measures the time taken to traverse the lens from one side to the other one
If the traverse time is more than the limit 40 or 50 ms, a pole-slip is declared. If the complex
impedance Z(R, X) exits the lens on the same side it entered, then it is a stable case and the
protected machine is still in synchronism. If a pole-slip has been detected, then it is determined in
which zone the centre of oscillation is located. If the number of actual pole-slips exceeds the
maximum number of allowed pole-slips in either of the zones, a trip command is issued taking
care of the circuit breaker safety.
Section 7 1MRK 502 066-UUS B
Impedance protection
386
Technical manual
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