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Functions
2.18.2 Setting Hints
General
Pickup
Impedance
Settings
142
The out-of-step protection is only effective and accessible if this function has been set
during the configuration of the protective functions (Section 2.2, address 0135, OUT-
OF-STEP = Enabled. Set Disabled if the function is not required. Address 3501
OUT-OF-STEP is used to switch the function ON or OFF, or to block only the trip
command (Block Relay).
The out-of-step protection operates only when the positive sequence component of
the currents has exceeded a minimum threshold 3502 I1> RELEASE (overvoltage
pickup). As out-of-step conditions are symmetrical occurrences, a maximum value of
negative sequence current 3503 I2< RELEASE must not be exceeded.
The determining factor for overcurrent setting I1> RELEASE is the maximum possible
operating current. Pickup under conditions of permissible overload should be ex-
cluded. The setting should therefore be set above the maximum anticipated (over-)
load current (at least 120 % I
thresholds can be chosen, so that the measurement (see Figure 2-68) may be
released all the time. As out-of-step conditions are symmetrical occurrences, the
pickup threshold of the negative sequence component of the current I2< RELEASE
should be set to approx. 20 % I
The measured impedances during power swing conditions are decisive for the
settings. For the direction to the machine (as viewed from the location of the voltage
transformers), the power swing reactance of the machine must be considered, which
is approximately the transient reactance X
calculate the secondary transient reactance and set it for Z
Locus diagram
of power swing
impedance
Figure 2-69
Power Swing Polygon
. Depending on network conditions, smaller pickup
N
.
N
' of the machine. Consequently, you will
d
Im(Z)
Z
d
Z
–Z
d
c
Characteristic 2
Z
c
Characteristic 1
ϕ
P
Z
b
≈ X
' (see Figure 2-69).
b
d
ü
≈ (0.7 to 0.9) Z
ý
K Transf
þ
Z
a
ü
)
Re(Z
≈ X
ý
'
d
þ
C53000-G1176-C149-3
7UM62 Manual
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