Figure 159: Out Of Step Logic Diagram - GE MiCOM P40 Agile Technical Manual

P543i/P545i
The Out-of-Step tripping time delay (Tost), delays the OST tripping command until the angle between internal
voltages between the two ends are at 240 degrees closing towards 360 degrees. This limits the voltage stress
across the circuit breaker. If a fault occurs during the swing condition, the Out-of-Step tripping function is blocked.
The Out-of-Step algorithm is completely independent from the distance elements and the power swing detection
function. The load blinder does not affect the OST characteristics. In common with other similar functions, a
minimum positive sequence current of 5%In is needed for Out-of-Step operation.
4.3 OUT OF STEP LOGIC DIAGRAM
554
Start Z5
555
Start Z6
delta T
OST Mode
OST Disabled
Pred. OST Trip
Pred. & OST Trip
OST Trip
555
Start Z6
V02761

Figure 159: Out of Step logic diagram

4.4 OST APPLICATION NOTES
This product provides integrated Out-of-Step protection, which avoids the need for a separate stand alone Out-of-
Step device. This section provides guidance on how to configure Out of Step protection.
If you are going to use either of the predictive OST options (Pred. OST Trip or Pred. & OST Trip) you
must conduct detailed system studies to determine accurate settings. This is because high setting accuracy is
needed to avoid premature system splitting in the case of severe power oscillations that do not lead to pole slip
conditions.
Using the non-predictive OST Trip setting is simpler. You can can set it by knowing just the total system impedance,
Z , and the system split points.
T
4.4.1 SETTING THE OST MODE
The OST Mode setting provides four options:
●
OST Disabled
● Pred. OST Trip
● OST Trip
● Pred. & OST Trip
Setting OST Trip is the most commonly used approach when this protection is applied. OST Trip should be
used when Out-of-Step conditions are probable. If Out-of-Step conditions are detected, the OST command will be
issued to split the system at the pre-determined points. A disadvantage of the OST Trip option compared with
P54x1i-TM-EN-1
&
25ms
&
0
t
0
&
&
1
&
&
1
Note : R1 is measured resistive component of positive sequence impedance
tost
t
≥
1
0
Polarity Reversed?
&
Polarity detector
Reset function
Not reversed
Chapter 10 - Power Swing Functions
Fault detected
& 551
Pred. OST
553
&
≥
1
Reset function
OST
&
285