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.42Easy
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.43Easy
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.44Medium
In load flow analysis using Newton-Raphson method, what determines the convergence rate?
Answer: B
The convergence rate of Newton-Raphson method is determined by the Jacobian matrix's condition number and the initial guess proximity to solution.
Q.45Medium
What is the primary advantage of using HVDC transmission over HVAC for long distances?
Answer: C
HVDC reduces I²R losses (proportional to current squared) and eliminates reactive power flow, making it ideal for long-distance bulk power transmission.
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Q.46Medium
Which protection scheme is typically used for protecting transmission lines in Indian grid?
Answer: B
Distance relays provide selective protection for transmission lines by measuring impedance from relay location to fault point, standard in Indian POWERGRID.
Q.47Medium
In a 3-phase balanced fault at a bus, what is the fault current expression for a synchronous generator?
Answer: A
Subtransient reactance (Xd'') is used immediately after fault occurrence. Fault current = V/Xd'' for a 3-phase symmetrical fault at the generator terminals.
Q.48Medium
What is the economic dispatch problem in power systems?
Answer: A
Economic dispatch optimally allocates power generation among committed units to minimize fuel costs while satisfying load demand and operational constraints.
Q.49Easy
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.50Medium
What is the relationship between power factor and reactive power in a 3-phase system?
Answer: A
Reactive power Q = P × tan(φ), where φ is the phase angle between voltage and current. This fundamental relationship determines VAR compensation requirements.
Q.51Medium
In voltage stability analysis, what does the P-V curve represent?
Answer: A
P-V curves show how voltage varies with increasing active power at a bus. The nose point indicates the maximum power that can be transmitted before voltage collapse.
Q.52Medium
What is the primary purpose of a phasor measurement unit (PMU) in modern Indian grids?
Answer: B
PMUs measure voltage and current phasors synchronized via GPS, enabling real-time monitoring and control. India has deployed PMUs across POWERGRID network for situational awareness.
Q.53Hard
In transient stability studies, which machine variable is most critical for assessing first-swing stability?
Answer: A
Speed deviation determines if the generator can maintain synchronism during the first swing after a disturbance. Excessive Δω leads to loss of synchronism.
Q.54Hard
Which FACTS device provides independent control of both voltage magnitude and phase angle?
Answer: C
UPFC can independently control transmission line voltage magnitude, phase angle, and impedance simultaneously using combined series-shunt compensation.
Q.55Hard
What is the critical clearing angle in transient stability analysis?
Answer: A
Critical clearing angle is the maximum rotor angle at fault clearing beyond which the system loses synchronism. It determines the maximum fault clearing time.
Q.56Easy
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.57Hard
What is the primary mechanism of voltage instability in power systems?
Answer: A
Voltage instability occurs when reactive power demand exceeds generation and compensation capabilities, leading to progressive voltage decline and potential collapse.
Q.58Medium
In selective fuse coordination, which fuse should operate first during a downstream fault?
Answer: B
Selective coordination requires the fuse nearest to the fault to operate first, isolating only the faulted section while maintaining service to other areas.
Q.59Hard
Which formula represents the swing equation for a synchronous machine during a disturbance?
Answer: C
The swing equation 2H(d²δ/dt²) = Pm - Pe - D(dδ/dt) describes rotor angle dynamics, where H is inertia constant, Pm is mechanical power, Pe is electrical power, and D is damping coefficient.
Q.60Medium
What is the primary function of phase-shifting transformers in Indian grid operation?
Answer: A
Phase-shifting transformers control power flow by introducing a phase shift between primary and secondary voltages, enabling effective power flow management on parallel transmission corridors in Indian grid.
