P54x/EN OP/La4 Operation
(OP) 5-48
MiCOM P543, P544, P545 & P546
OP
1.20.1.1 Characteristic (Distance option only)
Both polygon characteristics are independent and have independent settings for their
respective reactance and resistive reaches.
Out of step trip
R
Z5
ZL
Z6
Z5'
Z6'
R5
R6R5'R6'
Predictive Out of
step trip
+jX
Recoverable swing
Figure 27 Out of step detection characteristic (Distance option only)
Both the inner (Zone 5) and outer (Zone 6) characteristics, as shown above, are settable in
positive sequence impedance terms to ensure correct Out of Step detection during open
pole swing conditions. Hence, there is only one Z5 and Z6 positive sequence impedance
polygon characteristic instead of 6 characteristics for each measured loop. The measured
positive sequence impedance is calculated as:
Z1 = V1/I1
Where V1 and I1 are positive sequence voltage and current derived from the measured
phase quantities. Note that during symmetrical power oscillations, there is no difference
between phase impedance loops and positive sequence impedance loop, whilst for the open
pole oscillations the phase and positive sequence impedances are different. This fact must
be taken into account during testing/commissioning.
All four resistive blinders are parallel, using the common angle setting ‘α’ that corresponds to
the angle of the total system impedance ZT (= ZS + ZL + ZR), where ZS and ZR are
equivalent positive sequence impedances at the sending and receiving ends and ZL positive
sequence line impedance. Tilting of the reactance line and residual compensation is not
implemented.
In Figure 26, the solid impedance trajectory represents the locu
s for the non-recoverable
power oscillation, also known as pole slip or out of step condition. The dotted impedance
trajectory on the other hand represents a recoverable power oscillation, usually called
swings.
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