Transmission and Distribution Systems MCQs (Part-2)
Which of the following is the primary component of overhead transmission lines?
A Transformer
B Insulator
C Conductor
D Switchgear
The primary component of overhead transmission lines is the conductor, which carries the electrical current. These conductors are typically made of materials like aluminum, which are efficient and lightweight, ensuring the power is transmitted effectively.
What does a step-down transformer do?
A Decrease voltage
B Filter signals
C Increase voltage
D Regulate current
A step-down transformer reduces high voltage to lower voltage levels, making it suitable for residential and commercial power use. The decrease in voltage ensures that power is safe for domestic consumption.
What is the primary function of a substation in a power distribution network?
A Increase voltage
B Store energy
C Regulate frequency
D Step-down voltage
A substation’s primary function is to step down high-voltage electricity from transmission lines to lower, usable voltages for local distribution. This ensures safe and efficient power delivery to homes and industries.
What causes line impedance in transmission lines?
A High voltage
B Length of the line
C Temperature changes
D Conductor material
Line impedance is primarily caused by the physical length of the transmission line. Longer lines increase resistance, which results in power loss and reduced transmission efficiency. Minimizing line length helps reduce impedance.
Why is aluminum commonly used as a conductor in transmission lines?
A Lightweight
B Expensive
C Non-corrosive
D High resistance
Aluminum is commonly used in transmission lines because it is lightweight, making it easier to handle and install. It also has good conductivity, making it a cost-effective material for overhead conductors.
Which of the following is a common method for reducing power losses in transmission lines?
A Reduce current
B Increase insulation
C Use low resistance cables
D Increase voltage
Using low-resistance cables reduces power losses by minimizing energy dissipation as heat. High-resistance cables cause more energy loss, so choosing cables with lower resistance improves overall transmission efficiency.
What is the main reason for using overhead lines instead of underground cables for transmission?
A Safety
B Cost-effective
C Better power quality
D Easier to maintain
Overhead lines are more cost-effective than underground cables, as they are cheaper to install and maintain. Underground cables, although safer and more visually appealing, are more expensive due to their installation complexity.
What is the typical voltage range for low voltage distribution networks?
A 400-500 V
B 230-400 V
C 100-500 V
D 1-11 kV
Low voltage distribution networks typically operate within the range of 230-400 V. This voltage range is standard for residential and small commercial electricity supply, ensuring the power is safe and usable for everyday applications.
What is the effect of line inductance in transmission lines?
A Increased voltage
B Voltage fluctuation
C Reactive power
D Power loss
Line inductance contributes to the generation of reactive power in transmission lines. Inductance causes current to lag behind the voltage, which affects power quality and needs to be managed to avoid inefficiencies in the system.
Why are insulators important in transmission lines?
A Support conductors
B Reduce power loss
C Protect against voltage spikes
D Regulate current flow
Insulators are crucial because they support the conductors and prevent electrical current from flowing to the ground or other structures. They ensure that electricity flows safely through the conductors without causing short circuits or power loss.
What is a major challenge in overhead transmission lines?
A High voltage
B Low resistance
C Voltage regulation
D Line sag
Line sag is a common challenge in overhead transmission lines. It occurs due to the weight of the conductor and environmental factors such as wind and temperature, which can cause the line to droop and affect performance.
How does voltage regulation affect power distribution?
A Controls power flow
B Stabilizes frequency
C Maintains voltage levels
D Reduces power loss
Voltage regulation is crucial in power distribution because it ensures that the voltage remains constant, even when there are fluctuations in demand or other conditions. This is important for protecting electrical equipment and maintaining power quality.
What does the term “corona discharge” refer to in transmission lines?
A Voltage drop
B Ionization of air
C Power loss due to heat
D Insulation failure
Corona discharge occurs when the electric field around a conductor is strong enough to ionize the surrounding air, leading to partial electrical breakdown. This phenomenon results in power loss and can cause interference with communication signals.
Which of the following is typically used to protect electrical systems from faults?
A Circuit breaker
B Inductor
C Capacitor
D Voltage regulator
A circuit breaker is used to protect electrical systems from faults by automatically disconnecting the power supply in the event of an overload or short circuit. This prevents damage to the system and enhances safety.
What is the typical voltage for medium voltage distribution systems?
A 400 kV
B 11 kV
C 1 kV
D 110 kV
Medium voltage distribution systems usually operate at 11 kV. This voltage level is ideal for transmitting power over short distances, typically from substations to neighborhoods or smaller industries, before it is further stepped down.