What is the main purpose of high-voltage transmission lines?
A To reduce power factor
B To minimize power losses during long-distance power transfer
C To increase line capacitance
D To regulate system frequency
High-voltage transmission lines reduce current for a given power, minimizing resistive losses (I²R losses) during long-distance power transfer.
Which system is primarily used for local distribution of electricity?
A High-voltage transmission system
B Medium-voltage system
C Low-voltage distribution system
D Grid interconnection system
Low-voltage systems distribute power to residential and commercial consumers, ensuring safety and compatibility with household appliances.
What material is commonly used for overhead line conductors?
A Iron
B Steel
C Aluminum
D Silver
Aluminum is lightweight, cost-effective, and has good conductivity, making it ideal for overhead line conductors.
What is the purpose of an insulator in a power system?
A To support the conductor and prevent leakage currents
B To increase voltage
C To regulate current
D To increase inductance
Insulators prevent electrical currents from flowing to the supporting structures, ensuring safety and efficient operation.
What is the primary role of a step-up transformer?
A To increase the frequency
B To reduce transmission losses by increasing voltage
C To balance load
D To stabilize current
Step-up transformers increase voltage, which reduces current for the same power, minimizing resistive losses during transmission.
Which phenomenon leads to ionization of air around high-voltage conductors?
A Corona discharge
B Ferranti effect
C Dielectric breakdown
D Eddy current loss
Corona discharge occurs when the electric field strength around a conductor exceeds the breakdown strength of air, causing ionization and energy loss.
What is the primary purpose of a substation in a power system?
A To generate electricity
B To step up or step down voltage levels
C To store energy
D To improve conductor efficiency
Substations adjust voltage levels between transmission and distribution systems, enabling efficient and safe power delivery.
What is the role of capacitance in long transmission lines?
A Increases power losses
B Causes a rise in voltage at the receiving end under light loads (Ferranti effect)
C Reduces inductance
D Reduces line resistance
Capacitance in long transmission lines contributes to the Ferranti effect, causing a voltage rise at the receiving end under light-load conditions.
What is the primary function of a lightning arrester in a power system?
A To step up voltage levels
B To protect the system from overvoltage due to lightning strikes
C To regulate power factor
D To reduce transmission losses
Lightning arresters divert high-voltage surges caused by lightning strikes to the ground, protecting electrical equipment from damage.
What is the purpose of a circuit breaker in a power system?
A To step down voltage levels
B To isolate faulty sections of the system during faults
C To regulate current
D To increase line impedance
Circuit breakers detect faults, such as overcurrent, and automatically disconnect the faulty section to prevent damage to the system.
What is the primary role of grounding in a power system?
A To increase voltage
B To provide safety by dissipating fault currents into the ground
C To balance load
D To reduce inductance
Grounding provides a path for fault currents to safely flow into the earth, ensuring protection of both equipment and personnel.
What is the main advantage of integrating renewable energy into the power grid?
A Increased transmission losses
B Sustainable and environmentally friendly energy supply
C Increased complexity of the grid
D Higher system frequency
Integrating renewable energy sources like wind and solar reduces reliance on fossil fuels, promoting sustainability and reducing environmental impact.
What is the role of a smart meter in a power system?
A To step up voltage
B To monitor and record energy usage in real-time
C To balance load across phases
D To reduce line impedance
Smart meters provide real-time data on energy consumption, improving billing accuracy and enabling efficient energy management.
What is the main purpose of reactive power in a power system?
A To perform useful work
B To support voltage levels and maintain system stability
C To reduce power losses
D To increase current flow
Reactive power is essential for maintaining voltage stability and ensuring the proper operation of electrical equipment like transformers and motors.
What is the effect of line inductance on the transmission system?
A It increases line resistance
B It opposes changes in current and contributes to voltage regulation
C It reduces voltage levels
D It increases capacitance
Inductance in transmission lines creates a magnetic field around the conductor, opposing any changes in current and influencing voltage levels.
What is the primary function of a capacitor bank in a power system?
A To supply active power
B To provide reactive power and improve power factor
C To increase voltage levels
D To reduce current
Capacitor banks provide reactive power, compensating for inductive loads and improving the power factor of the system.
What is the effect of capacitance in long transmission lines under light load conditions?
A Causes a decrease in voltage at the receiving end
B Causes a voltage rise at the receiving end (Ferranti effect)
C Reduces line impedance
D Increases line resistance
The Ferranti effect occurs in long transmission lines when the receiving end voltage becomes higher than the sending end voltage under light-load conditions due to the capacitance of the line.
What is the function of a relay in a power system protection scheme?
A To measure power flow
B To detect abnormal conditions and trigger protection devices
C To store energy for future use
D To increase line impedance
Relays monitor the system for faults such as overcurrent or short circuits and send signals to circuit breakers to disconnect the faulty section, protecting the system from damage.
What is the primary function of a microgrid?
A To increase line resistance
B To provide localized power supply and integrate renewable energy
C To step up voltage levels
D To reduce line capacitance
Microgrids are localized energy systems that can operate independently or in conjunction with the main grid, providing reliable power and supporting renewable energy integration.
What is the primary advantage of using smart meters in a distribution system?
A To increase line inductance
B To provide real-time data for better energy management and billing
C To balance the load across phases
D To reduce power factor
Smart meters enable real-time monitoring of energy consumption, improving energy management, accurate billing, and enabling dynamic pricing.
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.
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 substation isolator?
A To interrupt high fault currents
B To connect or disconnect parts of the substation during no-load conditions
C To regulate voltage
D To protect equipment from lightning
Isolators are used to disconnect a section of the substation for maintenance or repair but cannot operate under load conditions. They are operated only after the circuit breaker has isolated the load.
What is the main purpose of circuit breakers in substations?
A To increase voltage
B To automatically disconnect during fault conditions
C To isolate sections for maintenance
D To control frequency
Circuit breakers automatically interrupt current flow in case of faults, protecting equipment and preventing damage in the system.
What is the typical frequency of power systems in most countries?
A 50 Hz
B 60 Hz
C 100 Hz
D Both a and b depending on the country
Power systems operate at 50 Hz in many countries (e.g., India), while some (e.g., the USA) use 60 Hz. Substations are designed to maintain these frequencies.
What are the two main types of substations?
A AC and DC substations
B Transmission and distribution substations
C High-voltage and low-voltage substations
D Compact and renewable energy substations
Transmission substations handle high voltage and long-distance power transfer, while distribution substations step down voltage for consumer use.
Which system in substations manages monitoring, control, and data acquisition remotely?
A Relay system
B SCADA system
C Insulation system
D Lightning protection system
SCADA (Supervisory Control and Data Acquisition) enables remote monitoring, data collection, and control of substations, enhancing system efficiency and reliability.