Measures for Improvement of Transient Stability (Warranty of Dynamic Stability) U‘p should be large (overexcited operation at synchronous
machines) U‘N should be large (high voltage level in the grid) U‘p should be large in the case of a fault (field forcing) X should be small (high degree of meshed networks) δ perm. should be small (fast fault clearing time, especially at
faults close to the power plant; dead time should be so optimised, that the changing of the rotor angle is very small during an unsuccessful AR at the critical machine for the stability) Pmechanical decreasing during short circuit (total or partly closing
of valves (fast valving)) P increasing with additional load impedance during a short
2. The crossing of the middle line (red) is the criterion of the counter increasing 3. Increasing the counter of characteristic in which the middle line was crossed 4. The increasing of the counter is active, if the vector goes out of the power swing polygon
Supervision of the impedance vector if he enters and leaves the blinders - logic and timers are than active. The double blinder principle is used in the case of a faster decision between short circuit and power swing (indirect speed measurement via the time (∆t) in which the vector is between the internal and external blinder) The superimposed impedance characteristic is a MHO - circle. Siemens. Innovation for generations.
Dynamic Test of 7UM62 with Real Time Simulator (RTDS) Test Configuration Impedance protection zones Z2 Z1 ALF1´
Load
ALF2´ ≠
G 7UM62 ALF: Actual Accuracy limiting factor of CT
Dynamic Test of 7UM62 with RTDS RMS Fault Record (Fault Duration 300ms)
Positive Sequence Current Positive Sequence Voltage Resistance
Reactance
After switching off of the short circuit a swing swing occurs. The out of step protection trips, because the power swing centre was in the generator unit.
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