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Which of the following is the short term stability in a generator driven system?
Rotor-angle stability
Short term voltage stability
Frequency Stability
Long-term voltage stability
Rotor-angle stability
Quick Summary: Rotor-angle stability is classified as a short-term stability phenomenon because it relates to the ability of interconnected synchronous machines to maintain synchronism after being subjected to a disturbance. It involves the dynamic interaction of generator torques and is typically analyzed within a timeframe of a few seconds.
Rotor-angle stability is classified as a short-term stability phenomenon because it relates to the ability of interconnected synchronous machines to maintain synchronism after being subjected to a disturbance. It involves the dynamic interaction of generator torques and is typically analyzed within a timeframe of a few seconds.
Mdt2d2δ=Pm−Pe — The Swing Equation governing rotor angle dynamics
Pe=XEVsinδ — Power-angle relationship for a cylindrical rotor generator
The principle relies on the balance between electromagnetic torque and mechanical torque. When a disturbance occurs, the rotor speed deviates from the synchronous speed, causing a change in the power angle δ. If the system is stable, the restoring torque brings the angle back to equilibrium; if the deviation persists or grows due to insufficient synchronizing torque, the machine loses synchronism (pole slipping).
Short-term stability includes Rotor-angle stability and Short-term voltage stability.
Rotor-angle stability is concerned with the ability to maintain synchronism after large or small disturbances.
The time frame for rotor-angle stability analysis is typically 1 to 5 seconds.
Long-term stability involves equipment response like OLTC and secondary control (minutes).
Allows for precise assessment of system limits during transients.
Facilitates the design of robust Power System Stabilizers (PSS).
Highly non-linear and computationally intensive to simulate.
Sensitive to network topology changes and fault locations.
Transient stability studies following transmission line faults.
Dynamic security assessment in real-time control centers.
Frequency stability is generally considered a medium-to-long term phenomenon due to the influence of governor and turbine response times.
Option B (Short term voltage stability) is also a short-term phenomenon, but Rotor-angle stability is the fundamental definition for generator-driven systems responding to angular oscillations.
Long-term voltage stability (Option D) is associated with slow-acting mechanisms like tap changers and boiler dynamics.
A is correct — Rotor-angle stability is the fundamental short-term stability concern in generator-driven systems, focusing on the ability of synchronous machines to remain in synchronism after disturbances.
Always remember that short-term stability (0-10 seconds) is dominated by electromagnetic and electromechanical effects, while long-term stability (>10 seconds) is dominated by thermal and mechanical control processes.