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.62Medium
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.63Medium
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.64Medium
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.65Medium
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.
Advertisement
Q.66Medium
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.67Medium
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.68Medium
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.69Medium
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.70Medium
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.71Medium
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.72Medium
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.73Medium
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.74Medium
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.75Medium
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.76Medium
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.77Medium
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.78Medium
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.80Medium
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.
