Transmission and Distribution Systems MCQs (Part-12)
What is the main purpose of high-voltage transmission lines?
A To reduce power factor
B To minimize power losses during long-distance power transfer
C To increase line capacitance
D To regulate system frequency
High-voltage transmission lines reduce current for a given power, minimizing resistive losses (I²R losses) during long-distance power transfer.
Which system is primarily used for local distribution of electricity?
A High-voltage transmission system
B Medium-voltage system
C Low-voltage distribution system
D Grid interconnection system
Low-voltage systems distribute power to residential and commercial consumers, ensuring safety and compatibility with household appliances.
What material is commonly used for overhead line conductors?
A Iron
B Steel
C Aluminum
D Silver
Aluminum is lightweight, cost-effective, and has good conductivity, making it ideal for overhead line conductors.
What is the purpose of an insulator in a power system?
A To support the conductor and prevent leakage currents
B To increase voltage
C To regulate current
D To increase inductance
Insulators prevent electrical currents from flowing to the supporting structures, ensuring safety and efficient operation.
What is the primary role of a step-up transformer?
A To increase the frequency
B To reduce transmission losses by increasing voltage
C To balance load
D To stabilize current
Step-up transformers increase voltage, which reduces current for the same power, minimizing resistive losses during transmission.
Which phenomenon leads to ionization of air around high-voltage conductors?
A Corona discharge
B Ferranti effect
C Dielectric breakdown
D Eddy current loss
Corona discharge occurs when the electric field strength around a conductor exceeds the breakdown strength of air, causing ionization and energy loss.
What is the primary purpose of a substation in a power system?
A To generate electricity
B To step up or step down voltage levels
C To store energy
D To improve conductor efficiency
Substations adjust voltage levels between transmission and distribution systems, enabling efficient and safe power delivery.
What is the role of capacitance in long transmission lines?
A Increases power losses
B Causes a rise in voltage at the receiving end under light loads (Ferranti effect)
C Reduces inductance
D Reduces line resistance
Capacitance in long transmission lines contributes to the Ferranti effect, causing a voltage rise at the receiving end under light-load conditions.
What is the primary function of a lightning arrester in a power system?
A To step up voltage levels
B To protect the system from overvoltage due to lightning strikes
C To regulate power factor
D To reduce transmission losses
Lightning arresters divert high-voltage surges caused by lightning strikes to the ground, protecting electrical equipment from damage.
What is the purpose of a circuit breaker in a power system?
A To step down voltage levels
B To isolate faulty sections of the system during faults
C To regulate current
D To increase line impedance
Circuit breakers detect faults, such as overcurrent, and automatically disconnect the faulty section to prevent damage to the system.
What is the primary role of grounding in a power system?
A To increase voltage
B To provide safety by dissipating fault currents into the ground
C To balance load
D To reduce inductance
Grounding provides a path for fault currents to safely flow into the earth, ensuring protection of both equipment and personnel.
What is the main advantage of integrating renewable energy into the power grid?
A Increased transmission losses
B Sustainable and environmentally friendly energy supply
C Increased complexity of the grid
D Higher system frequency
Integrating renewable energy sources like wind and solar reduces reliance on fossil fuels, promoting sustainability and reducing environmental impact.
What is the role of a smart meter in a power system?
A To step up voltage
B To monitor and record energy usage in real-time
C To balance load across phases
D To reduce line impedance
Smart meters provide real-time data on energy consumption, improving billing accuracy and enabling efficient energy management.
What is the main purpose of reactive power in a power system?
A To perform useful work
B To support voltage levels and maintain system stability
C To reduce power losses
D To increase current flow
Reactive power is essential for maintaining voltage stability and ensuring the proper operation of electrical equipment like transformers and motors.
What is the effect of line inductance on the transmission system?
A It increases line resistance
B It opposes changes in current and contributes to voltage regulation
C It reduces voltage levels
D It increases capacitance
Inductance in transmission lines creates a magnetic field around the conductor, opposing any changes in current and influencing voltage levels.
What is the primary function of a capacitor bank in a power system?
A To supply active power
B To provide reactive power and improve power factor
C To increase voltage levels
D To reduce current
Capacitor banks provide reactive power, compensating for inductive loads and improving the power factor of the system.
What is the effect of capacitance in long transmission lines under light load conditions?
A Causes a decrease in voltage at the receiving end
B Causes a voltage rise at the receiving end (Ferranti effect)
C Reduces line impedance
D Increases line resistance
The Ferranti effect occurs in long transmission lines when the receiving end voltage becomes higher than the sending end voltage under light-load conditions due to the capacitance of the line.
What is the function of a relay in a power system protection scheme?
A To measure power flow
B To detect abnormal conditions and trigger protection devices
C To store energy for future use
D To increase line impedance
Relays monitor the system for faults such as overcurrent or short circuits and send signals to circuit breakers to disconnect the faulty section, protecting the system from damage.
What is the primary function of a microgrid?
A To increase line resistance
B To provide localized power supply and integrate renewable energy
C To step up voltage levels
D To reduce line capacitance
Microgrids are localized energy systems that can operate independently or in conjunction with the main grid, providing reliable power and supporting renewable energy integration.
What is the primary advantage of using smart meters in a distribution system?
A To increase line inductance
B To provide real-time data for better energy management and billing
C To balance the load across phases
D To reduce power factor
Smart meters enable real-time monitoring of energy consumption, improving energy management, accurate billing, and enabling dynamic pricing.