In the 2024 Indian grid code, what is the minimum frequency threshold below which load shedding is mandatorily initiated?
Answer: B
As per latest POSOCO guidelines and Indian Grid Code 2024, automatic load shedding initiates at 48.5 Hz frequency threshold to maintain grid stability.
Q.22Hard
Which among the following is the correct formula for calculating bus voltage magnitude in Gauss-Seidel load flow method?
Answer: C
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)]
Q.23Easy
What is the primary purpose of shunt capacitors in power systems?
Answer: B
Shunt capacitors supply reactive power locally, improving voltage profile and reducing the burden on generators and transmission lines to supply reactive power.
Q.24Medium
Under what condition does maximum power transfer occur in a transmission line?
Answer: B
Maximum power transfer theorem states that maximum power is delivered when load impedance is the complex conjugate of source impedance.
Q.25Medium
In the context of Indian Power System, what does 'UI' (Unscheduled Interchange) in real-time market signify?
Answer: B
UI is the real-time balancing mechanism in Indian power market where deviations from scheduled power are settled at dynamic prices determined by frequency deviations.
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Q.26Medium
Which factor does NOT directly affect the surge impedance loading (SIL) of a transmission line?
Answer: C
SIL = V²/Z_c, where Z_c is surge impedance = √(L/C). It depends on L and C per unit length and frequency, but NOT on total line length.
Q.27Medium
What is the significance of 'P-Q capability curve' in generator operation?
Answer: A
The P-Q capability curve defines the operating region of a generator considering thermal limits, stability limits, and excitation limits for both active and reactive power.
Q.28Hard
In a 500 kV transmission line, if the receiving end voltage drops to 0.9 pu, what type of compensation is most critical?
Answer: C
For severe voltage drop (10%), both series compensation (to reduce voltage drop) and shunt compensation (to support receiving end voltage) are typically required.
Q.29Easy
Which type of fault in power system requires the fastest clearance to maintain stability?
Answer: B
Three-phase faults cause maximum current and power imbalance, requiring fastest clearance (typically 100-150 ms) to maintain transient stability.
Q.30Medium
What is the relationship between voltage stability limit and transmission line loading?
Answer: B
As reactive power demand increases with line loading, voltage stability margin decreases. The maximum power that can be transferred is limited by voltage stability.
Q.31Easy
In Indian grid operation, what is the nominal frequency specification?
Answer: C
As per Indian Grid Code 2024 and POSOCO standards, the nominal frequency is 50 Hz with a normal operating range of ±0.10 Hz (49.90-50.10 Hz).
Q.32Medium
Which FACTS device can simultaneously control both voltage and power flow independently?
Answer: C
UPFC has both series and shunt components, allowing independent control of voltage and power flow. It can inject voltage in both magnitude and phase.
Q.33Medium
What does the 'rotor angle' or 'power angle' represent in power system stability analysis?
Answer: A
The rotor angle (δ) is the angle between the generator's rotor magnetic field axis and the reference axis of the network voltage, critical for stability analysis.
Q.34Easy
In a 132 kV system, if the ground fault setting is 200 A, what is the corresponding relay pickup in percentage of line CT primary rating (2000 A)?
Answer: B
Relay pickup percentage = (200 A / 2000 A) × 100 = 10% of CT primary rating.
Q.35Easy
Which of the following correctly represents the relationship in per-unit system for power?
Answer: A
In per-unit system, power is expressed as P(pu) = P(actual)/P_base = P(MW)/S_base(MVA), where S_base is typically the system base MVA.
Q.36Medium
What is the primary function of a Static Synchronous Compensator (STATCOM) in modern power systems?
Answer: B
STATCOM uses power electronics to inject/absorb reactive power independently from active power, providing fast voltage support and damping of oscillations.
Q.37Hard
In transient stability assessment, what does the 'equal area criterion' determine?
Answer: B
Equal area criterion uses the swing equation graph to compare the accelerating area (energy added to rotor) with decelerating area (energy removed), determining stability.
Q.38Medium
Which parameter is most affected by temperature variation in overhead transmission lines?
Answer: B
Temperature causes resistance to change (R = R₀[1 + α(T-T₀)]) and significantly affects sag due to thermal expansion of conductor, impacting clearances and voltage drop.
Q.39Medium
In the latest Indian RE (Renewable Energy) integration guidelines 2024, what is the maximum renewable energy penetration level being targeted by 2030?
Answer: C
India's target for 2030 is 500 GW renewable capacity, aiming for approximately 60% of total electricity generation from renewable sources as per National Action Plan on Climate Change.
Q.40Easy
What is the primary reason for maintaining spinning reserve in power systems?
Answer: B
Spinning reserve (typically 5-10% of peak load) ensures that the system can respond to sudden load increases or unexpected generator tripping without frequency deviation beyond limits.
