What is the primary function of a circuit breaker in a power system?
Answer: A
Circuit breakers detect abnormal currents and automatically disconnect faulty sections to prevent equipment damage and cascading failures.
Q.82Medium
The stability of a power system depends on which of the following factors?
Answer: B
Power system stability is determined by the rotor dynamics characterized by inertia (M), damping (D), and synchronizing coefficient (Ks).
Q.83Easy
Which of the following is NOT a renewable energy source integrated into the Indian grid?
Answer: C
As of 2024-25, tidal energy has not been commercially integrated into the Indian grid on a significant scale, unlike solar, wind, and biomass.
Q.84Easy
What is the standard frequency of the Indian power grid?
Answer: A
India follows the 50 Hz standard frequency for AC power systems, as per IEC standards.
Q.85Easy
In a power system, the angle between voltage and current phasors is known as:
Answer: B
The phase angle (φ) between voltage and current phasors determines the power factor of the system.
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Q.86Medium
The per-unit (p.u.) system in power systems is used primarily to:
Answer: A
Per-unit system normalizes all quantities relative to chosen base values, simplifying analysis and comparison across different voltage levels and equipment ratings.
Q.87Medium
Which protective relay is used for phase-to-phase fault detection in transmission lines?
Answer: B
Differential relays compare currents at both ends of a line and trip if there is a mismatch indicating an internal fault.
Q.88Medium
A synchronous motor operating at no-load consumes:
Answer: B
At no-load, a synchronous motor supplies only magnetizing current (reactive power) to maintain the magnetic field.
Q.89Medium
The reactive power generated by an over-excited synchronous generator is:
Answer: B
Over-excitation increases the magnetic field, causing the generator to supply lagging reactive power to support system voltage.
Q.90Medium
What is the primary cause of voltage instability in a power system?
Answer: A
Voltage instability occurs when reactive power demand cannot be met, causing voltage collapse, particularly at weak points in the grid.
Q.91Hard
The swing equation of a synchronous machine is given by: 2H(d²δ/dt²) = Pm - Pe - D(dδ/dt). What does H represent?
Answer: A
H is the inertia constant (M/2×SB) representing the kinetic energy relative to the system base power.
Q.92Easy
In India's 2024-25 grid, which state has the highest installed renewable energy capacity?
Answer: A
Gujarat leads in combined renewable capacity including solar parks and wind farms as per latest 2024-25 CEA reports.
Q.93Hard
The critical clearing angle (δcr) in transient stability analysis represents:
Answer: A
δcr is the limiting rotor angle; if exceeded during a fault, the machine cannot return to synchronism even after fault clearance.
Q.94Medium
Power system harmonics in Indian grids are primarily caused by:
Answer: A
Modern non-linear loads like switch-mode power supplies, VFDs, and renewable energy inverters are major sources of harmonics in contemporary Indian grids.
Q.95Hard
The fault level (short-circuit capacity) at a bus is determined by:
Answer: A
Fault level = MVA base / (Zth in p.u.), where Zth is the equivalent impedance of the entire network.
Q.96Medium
In load flow analysis, which bus type is used to specify active power and voltage magnitude?
Answer: A
PV buses represent generators where active power injection and voltage magnitude are specified; reactive power is calculated.
Q.97Hard
The maximum power transfer in an AC transmission system occurs when the sending and receiving end voltages are:
Answer: C
Maximum power transfer (Pmax = V²/X) occurs when power angle δ = 90°, regardless of absolute voltage magnitudes.
Q.98Medium
Which of the following is a measure of power quality as per Indian Standards (IS 16001:2017)?
Answer: A
IS 16001:2017 defines power quality parameters including THD (Total Harmonic Distortion) and voltage flicker limits.
Q.99Medium
In a three-phase power system with balanced conditions, the zero-sequence current flows through:
Answer: A
Zero-sequence currents (equal in all three phases and same direction) require a return path through neutral or ground.
Q.100Easy
In a 400 kV transmission line in India's western grid, if the series reactance is 0.35 Ω/km and the line length is 250 km, what is the total series reactance of the transmission line?
Answer: A
Total series reactance = 0.35 Ω/km × 250 km = 87.5 Ω. This is a fundamental calculation for transmission line parameters commonly tested in GATE and ESE.
