Design - ABB RES670 Technical Manual

1MRK 511 408-UUS A
7.2.7.5
Phasor measurement unit RES670 2.2 ANSI
Technical manual
35
pos. seq. current in kA
trip command to CB
30
rotor angle in radian
25
20
current increases under
fault conditions
15
fault
occurs
10
← normal load current
5
rotor angle
←
0
-5
0 200
IEC10000115 V1 EN-US
Figure 48: Trip initiation when the break-time of the circuit breaker is known

Design

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.
very high currents due
to out-of-step condition
← after 1st
pole slip
fault cleared →
current decreases
trip command →
issued here
→
angle towards 0°
400 600 800
Time in milliseconds →
Section 7
Impedance protection
← 2nd
← min. current
← tBreaker = 60 ms
1000 1200
IEC10000115-1-en.vsd
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