Transmission and Distribution Systems MCQs (Part-14)
What is the main purpose of a distribution transformer?
A To step up voltage for long-distance transmission
B To step down voltage for local distribution
C To increase power factor
D To regulate frequency
Distribution transformers step down the high transmission voltages to lower levels that are suitable for residential, commercial, and industrial use.
What is the typical range of low-voltage distribution systems?
A 0–1 kV
B 1–33 kV
C 33–110 kV
D Above 110 kV
Low-voltage distribution systems typically operate within the 0–1 kV range, which is used for delivering power to homes and small businesses.
What is the main advantage of overhead lines over underground cables?
A Higher current carrying capacity
B Lower installation and maintenance cost
C Better insulation
D Higher efficiency
Overhead lines are generally less expensive to install and maintain than underground cables, though they are more exposed to environmental factors.
Why are conductors stranded in power systems?
A To improve power factor
B To increase mechanical strength and flexibility
C To reduce inductance
D To increase capacitance
Stranded conductors offer greater mechanical flexibility and strength, allowing them to withstand environmental factors like wind and temperature changes.
What is the purpose of a substation in a power system?
A To store energy for peak demand
B To regulate voltage and control power flow
C To generate electricity
D To increase conductor size
Substations are responsible for stepping up or stepping down voltage levels to ensure efficient power transmission and distribution.
What is the primary function of a capacitor bank in a power system?
A To reduce power factor
B To supply reactive power and improve power factor
C To store energy
D To regulate system frequency
Capacitor banks supply reactive power, compensating for the inductive load and improving the overall power factor of the system.
What is the typical voltage range for high-voltage transmission lines?
A 1–33 kV
B 33–110 kV
C 110–765 kV
D Above 765 kV
High-voltage transmission lines typically operate between 33 kV and 110 kV, facilitating efficient power delivery over long distances.
What is the purpose of line impedance in a transmission system?
A To reduce voltage levels
B To oppose the flow of current and affect power transfer
C To reduce current flow
D To regulate voltage levels
Line impedance includes both resistance and reactance. It limits the flow of current and affects the efficiency of power transfer across the transmission system.
What is the primary function of a relay in a power system?
A To step up voltage
B To detect faults and trigger a circuit breaker
C To improve power factor
D To regulate system frequency
Relays are protection devices used to detect faults and send a signal to circuit breakers to isolate faulty sections, ensuring system protection.
What does reactive power in a power system do?
A Increases active power
B Supports voltage levels and stabilizes the system
C Reduces system losses
D Reduces line impedance
Reactive power does not perform any useful work but is needed to maintain voltage stability and support the magnetic fields of inductive loads.
What is the function of a voltage regulator in a power system?
A To maintain a constant voltage level despite variations in load
B To increase system efficiency
C To balance load across phases
D To decrease transmission losses
Voltage regulators adjust the voltage to maintain a consistent level despite fluctuations in system load, ensuring stable power delivery.
What is the primary cause of line losses in power systems?
A Line resistance
B High voltage transmission
C Line capacitance
D Load balancing
Line losses are mainly caused by the resistance of the transmission line, which dissipates power in the form of heat. This increases with the length and resistance of the conductor.
What is the main purpose of load balancing in a power system?
A To distribute electrical load evenly across all phases
B To reduce voltage fluctuations
C To reduce system resistance
D To increase power factor
Load balancing ensures that power is distributed equally across all phases, improving system efficiency and preventing overloading of any single phase.
What is the function of a lightning arrester in a power system?
A To protect the system from overvoltage due to lightning strikes
B To step down voltage
C To regulate power factor
D To reduce system impedance
Lightning arresters are designed to protect electrical systems from high-voltage surges caused by lightning, directing the excess voltage safely to the ground.
What is the primary role of a relay in a protection system?
A To detect abnormal conditions and trigger protection devices
B To store energy for future use
C To regulate voltage levels
D To increase power factor
Relays are protection devices that monitor electrical circuits for abnormal conditions like overcurrent or fault. When such conditions occur, relays send a signal to disconnect the faulty section to prevent further damage.
What is the primary advantage of integrating renewable energy into power grids?
A Reduced environmental impact and sustainable energy supply
B Increased system losses
C Higher installation cost
D Reduced power quality
Integrating renewable energy into the grid reduces reliance on fossil fuels, decreases greenhouse gas emissions, and supports sustainable power generation, benefiting both the environment and society.
What is the primary function of a smart meter in a distribution network?
A To monitor and record energy usage in real-time
B To regulate voltage levels
C To store energy
D To balance load across phases
Smart meters provide real-time data on energy consumption, allowing for more accurate billing, better load management, and enabling utilities to monitor and optimize energy usage.
What is the function of a microgrid in modern power systems?
A To operate independently or in conjunction with the main grid for localized power supply
B To step up voltage levels
C To store renewable energy for future use
D To balance load across regions
Microgrids are small, localized grids that can operate independently or connect to the larger power grid, improving resilience, enabling renewable energy integration, and enhancing energy security.
What is the main cause of power loss in overhead transmission lines?
A Conductor capacitance
B Line resistance
C Overhead line tension
D Voltage regulation
Power loss in overhead lines is primarily caused by the resistance of the conductors, which dissipates electrical energy as heat.
What is the purpose of voltage regulation in a power system?
A To maintain a constant voltage at the load despite variations in load or generation
B To reduce line impedance
C To increase current flow
D To balance reactive power
Voltage regulation ensures that voltage levels at the consumer’s end remain stable despite fluctuations in load or generation, improving system reliability.