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.22Medium
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.23Medium
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.
Q.24Medium
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.25Medium
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.
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Q.26Medium
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.27Medium
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.28Medium
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.29Medium
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.30Medium
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.31Medium
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.
Q.32Medium
In a 400 kV transmission line, if the sending end voltage is 400 kV and receiving end voltage drops to 380 kV, what is the percentage voltage regulation?
A synchronous generator has a subtransient reactance (X''d) of 0.15 pu and transient reactance (X'd) of 0.25 pu. During a three-phase fault, which reactance is used for the initial fault current calculation?
Answer: C
Subtransient reactance X''d represents the initial response of the generator to a sudden disturbance and is used for calculating the first few cycles of fault current.
Q.34Medium
Which protection scheme is mandated for inter-state transmission lines in India according to Grid Code 2023?
Answer: C
Indian Grid Code 2023 requires differential protection as primary with distance protection as backup for critical transmission lines to ensure faster fault clearance.
Q.35Medium
A capacitor bank rated 50 MVAR at 400 kV is to be switched in a power system. Which device is most suitable for controlled switching to avoid transient overvoltages?
Answer: C
Pre-insertion resistors and reactors limit the inrush current and transient overvoltages when capacitor banks are switched, ensuring smooth energization.
Q.36Medium
In the Indian power system, the frequency regulation bandwidth for Load Frequency Control (LFC) is typically maintained within:
Answer: A
As per CEA guidelines and recent Grid Code specifications, LFC keeps the system frequency within ±0.2 Hz of 50 Hz nominal frequency to ensure quality power supply.
Q.37Medium
A 50 MW, 11 kV, 50 Hz synchronous generator has an inertia constant H = 6 seconds. Calculate the kinetic energy stored in the rotor at rated speed.
Answer: B
KE = H × S where S = rated MVA. KE = 6 × 50 = 300 MJ. (H is defined as H = KE/MVA)
Q.38Medium
In a multi-machine power system stability study, which parameter is used to measure relative rotor angle instability between two generators?
Answer: B
The stability of a multi-machine system depends on relative rotor angles between machines. Loss of synchronism occurs when relative rotor angle exceeds critical limits.
Q.39Medium
A STATCOM (Static Synchronous Compensator) is installed in a 220 kV network. In what mode should it operate to provide reactive power support during a voltage sag?
Answer: D
During voltage sag, STATCOM operates as a voltage source injecting capacitive reactive power (leading current) to support and restore the system voltage.
Q.40Medium
In selective coordination of protective devices, what is the minimum time interval required between the operation of primary and backup fuses as per Indian standards?
Answer: C
IS 1885 and IEEE standards recommend a minimum coordination time interval of 0.5 seconds between protective device operations to ensure selectivity.
