Power Systems Lab · 18 modules · all computed in your browser
Power swing & out-of-step
Swing locus on R-X, PSB blinders and ΔT timer, OOST on the way in/out, swing-centre voltage.
Loading module…
Power Systems Lab · 18 modules · all computed in your browser
Swing locus on R-X, PSB blinders and ΔT timer, OOST on the way in/out, swing-centre voltage.
Loading module…
Two-source equivalent
Electrical centre
20.0 Ω from relay
Max slip PSB detects
≈ 2.3 Hz (Δδ 25°)
Impedance locus on R-X
Green Z1, amber Z2, violet outer and red inner PSB blinders, white dashed total system impedance from −Zs to ZL + Zr. Equal sources swing along its perpendicular bisector.
Angle and swing-centre voltage
Relay events
Learn it
After a disturbance, the rotor angles of two groups of generators oscillate. The voltage at the electrical centre dips with δ, and the distance relay sees an impedance that moves smoothly across the R-X plane. A stable swing must not trip lines, because that would make things worse. An unstable, out-of-step condition has to be split at a pre-planned place. A fault makes the impedance jump in microseconds. A swing takes tens of milliseconds to cross the band between two concentric characteristics, and that timing difference is the basis of power-swing blocking (PSB).
Quiz · 0/3
1. Why does PSB use two concentric characteristics?
2. With equal source EMFs, the swing locus is…
3. What does |SCV| do as δ passes 180°?