What is the primary purpose of transmission lines in a power system?
A To generate electricity
B To transmit power over long distances
C To store energy for future use
D To convert AC to DC
Transmission lines are designed to carry electrical energy from generation stations to substations over long distances efficiently.
Which type of system is responsible for delivering power to end users?
A Transmission system
B Distribution system
C Substation system
D Generation system
Distribution systems deliver electrical energy from substations to consumers, typically at lower voltages suitable for end users.
Why are step-up transformers used in power systems?
A To increase current flow
B To increase voltage levels for efficient transmission
C To reduce transmission losses
D To stabilize frequency
Step-up transformers raise voltage, which reduces current for the same power, minimizing resistive losses during transmission.
What is the primary disadvantage of underground cables compared to overhead lines?
A Higher current carrying capacity
B Higher initial installation cost
C More exposure to environmental factors
D Lower insulation requirements
Underground cables are more expensive to install due to the need for excavation, insulation, and more maintenance compared to overhead lines.
What is the role of a substation in a power system?
A To store energy
B To regulate voltage and control power flow
C To generate electricity
D To increase conductor size
Substations regulate voltage, switch power flow, and step up or step down voltage for distribution.
What happens when the voltage in a transmission line exceeds the breakdown strength of air?
A Ferranti effect
B Corona discharge
C Dielectric breakdown
D Eddy current loss
Corona discharge occurs when the electric field around a conductor exceeds the breakdown strength of air, causing ionization and energy loss.
What is the primary advantage of aluminum over copper as a conductor?
A Higher resistance
B Lower weight and cost
C Better conductivity
D Easier to install
Aluminum is lighter and more cost-effective compared to copper, making it ideal for large-scale transmission applications.
What is the primary role of a suspension insulator in overhead transmission lines?
A To reduce line impedance
B To support the conductor and provide insulation
C To store energy
D To increase current carrying capacity
Suspension insulators are used to support conductors in high-voltage lines while providing electrical isolation from supporting structures.
What is the typical voltage range for high-voltage transmission lines?
A 11–33 kV
B 110–765 kV
C 33–110 kV
D 0–1 kV
High-voltage transmission lines typically operate in the range of 110 kV to 765 kV for efficient long-distance power transmission.
What is the purpose of reactive power management in a power system?
A To reduce system frequency
B To regulate voltage levels and improve power factor
C To store energy
D To increase transmission line losses
Reactive power is essential for voltage regulation and helps maintain the stability and efficiency of the power system.
What is the unit of apparent power in an AC system?
A Watt
B VA (Volt-Ampere)
C VAR (Volt-Ampere Reactive)
D Ohm
Apparent power combines active and reactive power and is measured in Volt-Amperes (VA).
What is the primary function of grounding in a power system?
A To increase voltage levels
B To dissipate fault currents safely into the ground
C To reduce inductance
D To stabilize frequency
Grounding ensures that fault currents are safely directed to the earth, protecting equipment and personnel from hazardous voltages.
What is the Ferranti effect in transmission lines?
A Voltage drop at the receiving end
B Voltage rise at the receiving end under light load conditions
C Increase in line resistance
D Reduction in capacitance
The Ferranti effect causes a voltage rise at the receiving end of a long transmission line under light-load conditions due to the line’s capacitance.
What is the primary cause of sag in transmission lines?
A High resistance
B Conductor weight and temperature changes
C Excessive current flow
D Poor insulation
Sag is primarily caused by the weight of the conductor and temperature variations, which lead to expansion or contraction of the wire.
What is the main advantage of aluminum over copper as a conductor?
A Higher resistance
B Lower weight and cost
C Better conductivity
D Easier to install
Aluminum is cheaper and lighter than copper, making it a more cost-effective material for overhead conductors.
What is the function of a lightning arrester in a power system?
A To step up voltage levels
B To protect the system from overvoltage caused by lightning strikes
C To regulate power factor
D To reduce current flow
Lightning arresters prevent damage from lightning surges by diverting the high-voltage surge to the ground.
What is the purpose of a smart meter in a distribution system?
A To step up voltage
B To measure energy usage and provide real-time data
C To balance load demand
D To reduce capacitance
Smart meters allow utilities and consumers to monitor real-time energy consumption, improving efficiency and enabling better billing practices.
What is the primary advantage of microgrids?
A They reduce power factor
B They provide localized and reliable power supply
C They increase transmission losses
D They eliminate voltage fluctuations
Microgrids are small-scale, localized energy systems that ensure reliable and flexible energy supply, often integrating renewable sources.
What is the primary cause of sag in transmission lines?
A High resistance
B Conductor weight and temperature changes
C Excessive current flow
D Poor insulation
Sag is primarily caused by the weight of the conductor and thermal expansion or contraction due to temperature variations.
What is the main advantage of aluminum over copper as a conductor?
A Higher resistance
B Lower weight and cost
C Better conductivity
D Easier to install
Aluminum is cheaper and lighter than copper, making it a more cost-effective material for overhead conductors.