3
Base
UBase
Z
IBase
=
EQUATION1883 V1 EN-US
(Equation 449)
The
ImpedanceZB is the reverse impedance as show in figure
ZB should be equal to the
generator transient reactance X'd. The impedance is given in % of the base impedance, see
equation
.
The
ImpedanceZC is the forward impedance giving the borderline between zone 1 and zone 2.
ZC should be equal to the transformer reactance ZT. The impedance is given in % of the base
impedance, see equation
.
The angle of the impedance line ZB – ZA is given as
AnglePhi in degrees. This angle is normally
close to 90°.
StartAngle: An alarm is given when movement of the rotor is detected and the rotor angle
exceeds the angle set for
StartAngle. The default value 110° is recommended. It should be
checked so that the points in the impedance plane, corresponding to the chosen
StartAngle
does not interfere with apparent impedance at maximum generator load.
TripAngle: If a pole slip has been detected: change of rotor angle corresponding to slip
frequency 0.2 – 8 Hz, the slip line ZA – ZB is crossed and the direction of rotation is the same as
at start, a trip is given when the rotor angle gets below the set
TripAngle. The default value 90°
is recommended.
N1Limit: The setting N1Limit gives the number of pole slips that should occur before trip, if the
crossing of the slip line ZA – ZB is within zone 1, that is, the node of the pole slip is within the
generator transformer block. The default value 1 is recommended to minimize the stress on
the generator and turbine at out of step conditions.
N2Limit: The setting N2Limit gives the number of pole slips that should occur before trip, if the
crossing of the slip line ZA – ZB is within zone 2, that is, the node of the pole slip is in the
external network. The default value 3 is recommended give external protections possibility to
split the network and thus limit the system consequencies.
ResetTime: The setting ResetTime gives the time for (PSPPPAM) function to reset after start
when no pole slip been detected. The default value 5s is recommended.
7.16.3.1
Setting example for line application
SEMOD172162-25 v3
In case of out of step conditions this shall be detected and the line between substation 1 and 2
shall be tripped.
IED
ZB
Line impedance = ZC
ZA = forward source impedance
IEC07000014_2_en.vsd
IEC07000014 V2 EN-US
Figure 249: Line application of pole slip protection
If the apparent impedance crosses the impedance line ZB – ZA this is the detection criterion of
out of step conditions, see figure
Section 7
1MRK 505 343-UEN B
Impedance protection
382
Application manual
Summary of Contents for Relion 670 series
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