Transmission and Distribution Systems MCQs (Part-5)
What is the primary advantage of using underground cables?
A Voltage stability
B Durability
C Safety
D Cost-efficiency
Underground cables are safer compared to overhead lines as they are protected from weather conditions, falling trees, and accidental contact. This makes them ideal for urban areas where safety and reliability are critical.
What is the main disadvantage of underground cables compared to overhead lines?
A Cost of installation
B Higher resistance
C Voltage regulation
D Insulation failure
Underground cables are significantly more expensive to install than overhead lines due to the need for digging trenches, laying the cables, and ensuring proper insulation. However, they offer better protection and aesthetics.
What is typically used to insulate underground power cables?
A Paper
B Rubber
C Oil
D PVC
PVC (Polyvinyl Chloride) is commonly used as an insulating material for underground cables. It is durable, cost-effective, and provides good protection against electrical leakage and environmental factors like moisture.
What is the primary function of overhead lines in power distribution?
A Step-down voltage
B Transmit power
C Increase current
D Control voltage
Overhead lines are primarily used to transmit electrical power from the generating stations to substations. They are preferred for long-distance transmission because they are cheaper and easier to maintain than underground cables.
What is the typical voltage level for low voltage overhead lines?
A 230 V
B 400 kV
C 1 kV
D 11 kV
Low voltage overhead lines typically operate at 230 V, which is the standard voltage for household power distribution. These lines are used to distribute power from the substation to homes and small businesses.
What is the key challenge in maintaining overhead lines?
A Insulation
B Corrosion
C Voltage regulation
D Line sag
Line sag is a common challenge in maintaining overhead lines. It refers to the downward displacement of conductors due to their weight and environmental factors like wind or temperature changes, which requires careful design and maintenance.
Why are overhead lines generally preferred in rural areas?
A Aesthetic value
B Easy maintenance
C Low voltage
D Cost of installation
Overhead lines are preferred in rural areas because they are easier and cheaper to maintain than underground cables. In rural locations, frequent access and low installation costs make overhead lines a more viable option.
What is the primary material used for overhead line conductors?
A Iron
B Copper
C Aluminum
D Steel
Aluminum is the most commonly used material for overhead line conductors because it is lightweight, cost-effective, and has a high electrical conductivity, making it ideal for long-distance power transmission.
What is the main reason for using high voltage in overhead transmission lines?
A Stabilize voltage
B Prevent sag
C Reduce current
D Control temperature
High voltage is used in overhead transmission lines to reduce the current flowing through the conductors. Lower current reduces energy losses due to resistance, making the transmission process more efficient, especially over long distances.
Which of the following is an environmental concern associated with overhead transmission lines?
A Power loss
B Voltage fluctuation
C Electromagnetic interference
D Aesthetic impact
Overhead transmission lines can have a significant aesthetic impact on landscapes, especially in scenic or residential areas. The presence of large poles and wires can detract from the natural beauty of the environment, leading to public opposition.
What is typically used to enhance the mechanical strength of overhead lines?
A Steel core
B Insulation material
C High voltage
D Aluminum wire
Overhead lines are often reinforced with a steel core inside the conductor wire to enhance their mechanical strength. This allows the lines to withstand environmental stress such as wind or ice loads without breaking or sagging excessively.
How are underground cables typically laid?
A Floating in water
B Above ground ducts
C Buried in trenches
D Overhead poles
Underground cables are laid in trenches to protect them from environmental damage. This installation method ensures that cables are shielded from weather-related wear and tear, offering greater durability and reliability for power distribution.
What is the primary advantage of using underground cables in urban areas?
A Aesthetic value
B Reduced interference
C Cost efficiency
D High voltage
Underground cables are often used in urban areas for aesthetic reasons. They are less visually intrusive compared to overhead lines, helping to preserve the appearance of cityscapes and reduce visual clutter, especially in high-density areas.
Which type of transmission line requires higher maintenance costs?
A Both
B Underground cable
C Overhead line
D None
While underground cables are safer and more aesthetically pleasing, they require higher maintenance costs compared to overhead lines. This is due to the complexity of repairs and the need for specialized equipment to access the cables when issues arise.
What is the main function of insulators in overhead transmission lines?
A Increase voltage
B Prevent electrical leakage
C Support the conductor
D Stabilize current
Insulators in overhead transmission lines are primarily used to support the conductors and prevent them from coming into contact with the ground or other structures. They also ensure electrical isolation between the conductors and supports, preventing electrical faults.