Alstom MiCOM P546 - 2.3.17.2 Blinder limits determination (Distance option only)

Application Notes P54x/EN AP/La4
MiCOM P543, P544, P545 & P546
(AP) 6-27
AP
Setting Option 4 provides 2 stages of Out of Step detection and tripping. If the power
system oscillation is very fast, the combination of ∆R and Delta t setting (as discussed
below) must be set in such a way that ‘Predictive OST’ operates. If however the oscillation is
slower, the condition for the ‘Predictive OST’ will not be met and the ‘OST’ will operate later
upon Z5 reset, providing that the change in polarity of the resistive component was detected.
This is to distinguish between a slower non-recoverable oscillation and recoverable swings.
2.3.17.2 Blinder limits determination (Distance option only)
Con
sider the Out of Step characteristic versus angle θ between two ends.
Out of step trip
R
Z5
ZL
Z6
Z5'
Z6'
R5 R6R5'R6'
Predictive Out of
step trip

+jX
ZR
ZS

ZT
Figure 7 Setting determination for the positive sequence resistive component R5
(Distance option only)
Firstly, determine the minimum inner resistive reach R5.
Figure 7 shows:
2
tan
2
min5


ZT
R
,
Where ZT is a total system positive sequence impedance that equals to ZS + ZL + ZS,
where ZS and ZR are equivalent positive sequence impedances at the sending and
receiving ends and ZL positive sequence line impedance. ‘θ’ is an angle difference between
the internal voltages at sending and receiving ends beyond which no system recovery is
possible.
The next step is to determine the maximum (limit value) for the outer resistive reach R6. It
must be insured that Point A in Figure 8 does not overlap with the load area for the worst
assume
d power factor of 0.85 and the lowest possible ZT angle α.