The per unit system in power system analysis is based on:
Answer: B
Per unit system uses selected base values for voltage, power, and impedance to normalize calculations across different system parts.
Q.42Easy
Which of the following represents the power factor in a three-phase AC circuit?
Answer: A
Power factor is defined as cos(φ), the cosine of the phase angle between voltage and current waveforms.
Q.43Easy
In the Indian power system (2024-25), what is the nominal frequency?
Answer: C
Indian power system operates at 50 Hz nominal frequency with allowed frequency variation of ±2% (49-51 Hz) as per grid code standards.
Q.44Easy
What is the primary role of a circuit breaker in a power system?
Answer: A
Circuit breakers carry normal load current and automatically open when fault current exceeds preset relay settings, isolating the faulty section.
Q.45Easy
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.
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Q.46Easy
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.47Easy
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.48Easy
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.49Easy
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.50Easy
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.
Q.51Easy
In Indian power systems, what is the standard voltage level for inter-state transmission?
Answer: B
Indian power system uses 220 kV and 400 kV for long-distance inter-state power transmission as per POWERGRID standards.
Q.52Easy
What is the purpose of a surge arrestor in a power system?
Answer: A
Surge arrestors protect equipment by limiting transient overvoltages caused by lightning strikes and switching operations.
Q.53Easy
Which of the following is NOT a function of a circuit breaker in power systems?
Answer: C
Circuit breakers handle fault interruption and normal switching, but voltage regulation is managed by transformers and SVCs, not circuit breakers.
Q.54Easy
Which Indian renewable energy initiative aims at 500 GW by 2030?
Answer: C
India's target to achieve 500 GW renewable energy capacity by 2030 is part of the Renewable Energy Capacity Addition Plan as per 2024-25 policy.
Q.55Easy
In the Indian grid code, what is the specified frequency band for normal operation?
Answer: C
As per Indian Grid Code 2023, the normal frequency band is 49.7-50.3 Hz. Operation outside this range triggers corrective actions.
Q.56Easy
Which of the following is NOT a component of the Indian National Load Despatch Centre (NLDC)?
Answer: C
NLDC coordinates scheduling and operation but does not directly maintain transmission lines. That responsibility lies with POWERGRID.
Q.57Easy
In load flow analysis, if a bus is specified with PV (constant voltage and active power), what variable is calculated?
Answer: B
In PV buses, active power (P) and voltage magnitude (V) are specified, and the load flow solution calculates the reactive power (Q) and voltage angle (δ).
Q.58Easy
Which type of power system stability is primarily concerned with the system's ability to maintain synchronism after a small disturbance?
Answer: B
Steady-state stability examines the system's response to small, gradual disturbances, while transient stability deals with large, sudden disturbances.
Q.59Easy
In the Indian grid, renewable energy penetration targets for 2024-2025 (non-hydro) approximately target what percentage of total generation capacity?
Answer: C
As per India's national renewable energy targets and Ministry of Power guidelines, approximately 45% non-fossil capacity addition is targeted for 2024-2025.
Q.60Easy
Which of the following voltage levels is NOT part of the Indian transmission network classification?
Answer: D
The standard Indian transmission voltage levels are 765 kV, 400 kV, 275 kV, and 220 kV. 150 kV is typically sub-transmission voltage level.
