Transmission and Distribution Systems MCQs (Part-3)
What is the primary function of a transformer in a transmission system?
A Increase resistance
B Decrease current
C Change voltage
D Increase current
The primary function of a transformer is to change the voltage level in a power transmission system. It either steps up or steps down the voltage, depending on the application, ensuring efficient transmission over long distances.
What is the typical voltage for low voltage distribution networks?
A 230 V
B 400 V
C 11 kV
D 100 V
Low voltage distribution systems typically use 230 V, which is standard for residential and small commercial applications. This voltage is safe for household appliances and ensures efficient and reliable power delivery.
Which of the following materials is most commonly used for transmission line conductors?
A Steel
B Copper
C Silver
D Aluminum
Aluminum is commonly used for transmission line conductors because of its light weight, low cost, and good conductivity. It is ideal for overhead lines due to its durability and efficiency in transmitting power.
What is the purpose of using insulators in power transmission?
A Regulate voltage
B Support conductors
C Protect from faults
D Prevent power loss
Insulators are used to support the conductors while preventing them from touching the ground or other structures. They ensure that electricity flows through the conductors without leakage or electrical faults, ensuring system safety.
Why are transmission lines generally placed at high voltage levels?
A To increase current
B To prevent overloading
C To reduce power loss
D To stabilize voltage
Transmission lines are placed at high voltage levels to reduce power loss. High voltage reduces current flow, which minimizes resistive losses in the transmission lines, making the power delivery more efficient over long distances.
What type of cable is commonly used for underground power transmission?
A Underground cable
B Overhead cable
C Fiber optic cable
D Coaxial cable
Underground cables are commonly used for power transmission in areas where overhead lines are impractical, such as densely populated urban areas. These cables offer better protection from weather but are more expensive and difficult to install.
What does a circuit breaker protect in an electrical system?
A Voltage
B Equipment
C Current
D Power
A circuit breaker is used to protect electrical equipment from damage caused by overloads or short circuits. It automatically interrupts the flow of electricity when an unsafe condition occurs, preventing potential damage to components.
What is the primary cause of voltage regulation issues in distribution networks?
A Low voltage
B Voltage fluctuation
C High resistance
D Overloading
Voltage regulation issues in distribution networks are primarily caused by overloading, which occurs when the system is required to deliver more power than it can handle. This leads to voltage drops, which can affect the performance of electrical equipment.
What role does line inductance play in transmission lines?
A Decreases current
B Controls frequency
C Generates reactive power
D Increases power
Line inductance contributes to the generation of reactive power, which is essential for maintaining voltage levels in transmission lines. It causes the current to lag behind the voltage, which can affect power quality and efficiency.
What is the purpose of a step-up transformer in a transmission network?
A Increase voltage
B Decrease voltage
C Control current
D Convert AC to DC
A step-up transformer is used to increase voltage before transmission over long distances. Higher voltage reduces the current, which minimizes energy loss and allows for more efficient power transmission across large areas.
What is a typical feature of a microgrid in a power system?
A Centralized power generation
B Low voltage only
C Uses renewable energy
D No backup power
Microgrids are often designed to integrate renewable energy sources like solar and wind, providing a local and sustainable power solution. They can operate independently from the main grid, offering resilience during power outages.
What does the term “sag” refer to in overhead transmission lines?
A Line voltage
B Conductor displacement
C Line extension
D Line tension
Sag refers to the downward displacement of conductors in overhead transmission lines due to gravity and environmental factors such as temperature changes. Proper design accounts for sag to ensure safe distances and reliable power transmission.
Which factor most significantly impacts power losses in transmission lines?
A Voltage level
B Conductor material
C Line resistance
D Line length
Line resistance is the primary factor affecting power losses in transmission lines. Higher resistance results in more energy being dissipated as heat, leading to increased power losses. Reducing resistance improves transmission efficiency.
What is the function of an earthing system in electrical distribution?
A Reduce power loss
B Prevent electric shock
C Control voltage
D Increase current flow
The earthing system provides a safe path for electrical faults to travel to the ground, preventing electric shock hazards. It ensures that exposed conductive parts of electrical systems are safely grounded, reducing the risk of accidents.
How does reactive power impact power systems?
A Increases voltage stability
B Causes power loss
C Improves power quality
D Reduces efficiency
Reactive power is crucial for maintaining voltage stability in power systems. While it does not perform useful work, it is necessary to maintain proper voltage levels, ensuring efficient operation and preventing voltage collapse in the grid.