Govt. Exams
Entrance Exams
Critical clearing angle is the maximum rotor angle at fault clearing beyond which the system loses synchronism. It determines the maximum fault clearing time.
UPFC can independently control transmission line voltage magnitude, phase angle, and impedance simultaneously using combined series-shunt compensation.
Speed deviation determines if the generator can maintain synchronism during the first swing after a disturbance. Excessive Δω leads to loss of synchronism.
Equal area criterion uses the swing equation graph to compare the accelerating area (energy added to rotor) with decelerating area (energy removed), determining stability.
For severe voltage drop (10%), both series compensation (to reduce voltage drop) and shunt compensation (to support receiving end voltage) are typically required.
The Gauss-Seidel iterative formula for bus voltage calculation uses the admittance matrix and network equations: V_i = (1/Y_ii)[P_i + jQ_i - Σ(Y_ij*V_j)]
Voltage collapse occurs when reactive power demand exceeds supply, causing progressive voltage reduction that destabilizes the system, as seen in 2012 Indian blackout.
N-R method converges based on good initial guesses (typically 1.0 pu) and the Jacobian matrix representing system sensitivity.
Under light load, capacitive reactance dominates, causing charging current and voltage rise at the receiving end above the sending end voltage.
Critical clearing time is the maximum duration a fault can exist before the system loses synchronism and becomes unstable.
