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Functions
Blocking of the
Impedance Stages
3-pole pickup
OFF
ON
"1"
3313 POWER SWING
I2<0,1I/In, Gen
I
L1
I
L2
I2
I
L3
3314 P/SPOL-TPOL
Tent
P/SPOL
Z(Tent)
Within
P/S polygon
Z(Tent-∆t)
P/SPOL
Outside
P/S polygon
TPOL
P/SPOL
Within
Trip polygon
Figure 2-63 Logic Diagram for the Power Swing Blocking of the Impedance Protection
2.17.3.1 Setting Hints
132
polygon P/SPOL and the trip polygon TPOL, and the rate of change ∆Z/∆t are
matched to one another in such a way that power swings are reliably detected and the
desired impedance zone (Z1 or Z1 & Z2) of the impedance protection is blocked. The
blocking remains effective until the measured impedance vector has left again the trip
polygon / power swing polygon, the impedance changes faster than the change rate,
or asymmetrical power conditions rule out the possibility of a power swing. The power
swing blocking time is also limited by a parameter setting
(T-ACTION P/S).
Power swing blocking is mostly used for impedance stage Z1, because the delay time
T1 for this stage is set low. Accordingly, a high delay time T2 must be set for zone Z2.
In the overreach zone Z1B no power swings can occur by definition, since the network
breaker is open and there is thus no second machine for power swings. Likewise, the
power swing blocking does not block the non-directional overcurrent stage (T3).
3966
Imp. picked up
Release of Power
swing blocking
&
3315 dZ/dt
<
∆Z / ∆t
Rate of
change
OR
>
The power swing blocking is only effective if address 3313 POWER SWING has been
set to ON.
A sensible compromise has to be found for the distance between the power swing
polygon and the trip polygon (parameter: P/SPOL-TPOL (address 3314) and for the
rate of change (parameter: dZ/dt (address 3315)). It must be kept in mind that the
rate of change is not constant and decreases with increasing proximity to the origin of
the coordinate system.The rate of change is also determined by power system condi-
tions, such as the impedance between the systems involved in the power swing, and
by the power swing frequency (see also Section 2.18 Out-of-Step Protection).
"Power swing
presumed"
S Q
&
&
&
R
Z(Tent)
Z(Tent-∆t) Last value outside P/S polygon
P/SPOL
TPOL
∆Z / ∆t
see Figure 2-61
Blocking
3976
Power Swing
3317 T-ACTION P/S
First value within P/S polygon
(at Tent)
Power swing polygon
Trip polygon
Rate of change of the impedance
vector
7UM62 Manual
C53000-G1176-C149-3
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