Q.1 1. What is the primary function of a distribution transformer in a power system?
Step up voltage for long-distance transmission
Step down voltage for local consumption
Regulate frequency
Measure power quality
Explanation - Distribution transformers reduce high transmission voltages to lower voltages suitable for residential and commercial use.
Correct answer is: Step down voltage for local consumption
Q.2 2. Which of the following is NOT a type of distribution network configuration?
Radial
Looped
Mesh
T-bridge
Explanation - Radial, looped, and mesh are common distribution configurations; a T-bridge is not used in standard distribution networks.
Correct answer is: T-bridge
Q.3 3. The voltage drop in a distribution feeder is mainly caused by:
Reactive power flow
Load impedance
Transformer tap settings
Insulation resistance
Explanation - Voltage drop occurs due to the resistance and reactance of the conductors carrying the load current.
Correct answer is: Load impedance
Q.4 4. What is the typical voltage level for low-voltage distribution networks?
33 kV
11 kV
400 V
500 kV
Explanation - Low-voltage distribution networks usually operate at 400 V (or 230 V single-phase) for consumer connections.
Correct answer is: 400 V
Q.5 5. In distribution automation, which device is used to remotely control switching operations?
Capacitor bank
Circuit breaker
Switching relay
Remote Terminal Unit (RTU)
Explanation - RTUs receive signals from SCADA systems and operate switches, breakers, and other devices in the field.
Correct answer is: Remote Terminal Unit (RTU)
Q.6 6. Which of the following best describes a ‘looped’ distribution network?
All feeders connected in series
Feeders connected in parallel only
Feeders interconnect to form loops
Feeders that are isolated during fault
Explanation - Looped networks have interconnections that allow alternative paths for power flow, improving reliability.
Correct answer is: Feeders interconnect to form loops
Q.7 7. What is the purpose of shunt capacitor banks in a distribution system?
Increase voltage drop
Reduce reactive power consumption
Provide protection during faults
Increase system frequency
Explanation - Shunt capacitors supply reactive power locally, improving voltage profiles and reducing losses.
Correct answer is: Reduce reactive power consumption
Q.8 8. Which protective device is typically used at the end of a distribution feeder to isolate faults?
Ground fault relay
Overcurrent relay
Load break switch
Fuse
Explanation - Fuses are simple, reliable devices that automatically disconnect feeders when fault currents exceed their rating.
Correct answer is: Fuse
Q.9 9. How does a recloser improve reliability in a distribution system?
It provides permanent protection for all faults
It automatically recloses after a brief fault interruption
It steps up voltage for long-distance transmission
It monitors power quality continuously
Explanation - Reclosers detect a fault, open the circuit, then attempt to reclose after a short interval, often clearing temporary faults.
Correct answer is: It automatically recloses after a brief fault interruption
Q.10 10. In a radial distribution network, what happens when a single fault occurs on a feeder?
All downstream customers lose power
Only the faulted line loses power
Only upstream customers lose power
No customers lose power
Explanation - A radial network has a single path; a fault interrupts all downstream loads.
Correct answer is: All downstream customers lose power
Q.11 11. What is the main advantage of using a transformer tap changer in distribution?
Adjusts system frequency
Reduces transformer size
Controls voltage level
Increases fault current
Explanation - Tap changers modify the turns ratio to regulate the output voltage and maintain voltage within limits.
Correct answer is: Controls voltage level
Q.12 12. Which type of load causes the most voltage sag in a distribution network?
Resistive heater
Motor startup
Light bulbs
Photovoltaic panels
Explanation - Induction motors draw high starting currents, causing temporary voltage dips or sags.
Correct answer is: Motor startup
Q.13 13. What is the purpose of a neutral grounding resistor in distribution systems?
To increase fault current
To limit fault current during ground faults
To step up voltage
To regulate power factor
Explanation - Resistors provide a controlled impedance, limiting the magnitude of ground fault currents.
Correct answer is: To limit fault current during ground faults
Q.14 14. In load flow analysis of a distribution network, which method is most commonly used for radial feeders?
Newton-Raphson
Gauss-Seidel
Backward/Forward Sweep
Direct Method
Explanation - The backward/forward sweep algorithm efficiently solves load flow for radial networks due to their tree structure.
Correct answer is: Backward/Forward Sweep
Q.15 15. The term 'distribution system reliability index (DSRI)' refers to:
Average outage duration per customer
Average number of outages per year per customer
Maximum permissible voltage drop
Minimum required transformer capacity
Explanation - DSRI measures how often customers experience outages, calculated as the number of outages divided by customers and years.
Correct answer is: Average number of outages per year per customer
Q.16 16. Which component is responsible for providing voltage support during peak demand periods in a distribution network?
Shunt reactors
On-load tap changers
Capacitor banks
Static VAR compensators
Explanation - Capacitor banks supply reactive power, reducing voltage drop during high load conditions.
Correct answer is: Capacitor banks
Q.17 17. In distribution network reconfiguration, the main goal is to:
Increase transformer size
Minimize power losses and improve voltage profiles
Eliminate all faults
Double the number of feeders
Explanation - Reconfiguration optimizes line currents and voltage levels, reducing losses and improving reliability.
Correct answer is: Minimize power losses and improve voltage profiles
Q.18 18. Which of the following is a typical protection scheme used for distribution lines?
Distance relay
Under-voltage relay
Differential relay
Over-load relay
Explanation - Distance relays detect fault impedance and are widely used for line protection in distribution systems.
Correct answer is: Distance relay
Q.19 19. What is the most common cause of corrosion in distribution overhead lines?
High wind speed
Presence of moisture and oxygen
High voltage
Low load factor
Explanation - Moisture and oxygen accelerate oxidation of conductors, leading to corrosion and increased resistance.
Correct answer is: Presence of moisture and oxygen
Q.20 20. Which device is used to disconnect a distribution feeder during maintenance?
Circuit breaker
Load break switch
Fuse
Automatic Recloser
Explanation - Load break switches can interrupt live circuits while being operated under load, suitable for maintenance.
Correct answer is: Load break switch
Q.21 21. The voltage regulation of a distribution transformer is defined as:
The change in voltage from no-load to full-load
The difference between primary and secondary voltages
The ratio of load to no-load current
The maximum voltage the transformer can handle
Explanation - Voltage regulation measures how much the transformer’s output voltage changes as load increases from zero to full.
Correct answer is: The change in voltage from no-load to full-load
Q.22 22. What is the primary reason for installing a surge arrester in distribution networks?
To limit voltage spikes during lightning strikes
To increase system frequency
To reduce harmonic distortion
To improve transformer efficiency
Explanation - Surge arresters protect equipment by clamping transient overvoltages caused by lightning or switching.
Correct answer is: To limit voltage spikes during lightning strikes
Q.23 23. In a three-phase distribution network, what does a 20% voltage sag mean?
Voltage drops by 20% during a fault
Voltage increases by 20% during a fault
Voltage remains constant
Voltage fluctuation of ±20%
Explanation - A 20% sag indicates the voltage has decreased to 80% of its nominal value temporarily.
Correct answer is: Voltage drops by 20% during a fault
Q.24 24. Which parameter is most affected by the installation of a capacitor bank in a distribution feeder?
System frequency
Load loss
Voltage rise
Insulation level
Explanation - Capacitor banks supply reactive power locally, raising voltage levels and reducing voltage drop.
Correct answer is: Voltage rise
Q.25 25. What is the typical rating of a single-phase distribution transformer for residential use?
5 kVA
10 kVA
50 kVA
100 kVA
Explanation - Residential distribution transformers are often rated around 5–10 kVA to supply typical household loads.
Correct answer is: 10 kVA
Q.26 26. In distribution system planning, the term 'load factor' refers to:
Maximum load divided by minimum load
Average load over a period divided by peak load
Load multiplied by voltage
Load divided by transformer capacity
Explanation - Load factor indicates how efficiently the system is used over time.
Correct answer is: Average load over a period divided by peak load
Q.27 27. Which of the following is a key benefit of smart meter deployment in distribution networks?
Improved voltage regulation
Real-time consumption data
Increased transformer life
Reduced harmonic distortion
Explanation - Smart meters provide detailed, time-stamped usage, aiding load forecasting and demand response.
Correct answer is: Real-time consumption data
Q.28 28. What type of fault causes the lowest fault current in a distribution system?
Phase-to-phase fault
Phase-to-ground fault
Three-phase fault
Double line-to-ground fault
Explanation - Phase-to-ground faults typically present higher impedance than line-to-line or three-phase faults, limiting current.
Correct answer is: Phase-to-ground fault
Q.29 29. The ‘feeder voltage drop’ can be minimized by:
Using higher resistance conductors
Installing voltage regulators at the load end
Increasing load levels
Removing all capacitors
Explanation - Voltage regulators adjust transformer taps to maintain voltage, reducing drop along the feeder.
Correct answer is: Installing voltage regulators at the load end
Q.30 30. In a distribution system, the term “neutral” primarily refers to:
The point where all three phases are connected
The path for fault current to return to the source
The high voltage bus
The grounding electrode
Explanation - Neutral provides a return path for current and is bonded to earth for safety.
Correct answer is: The path for fault current to return to the source
Q.31 31. Which device is commonly used to limit the charging current of photovoltaic arrays in distribution feeders?
Uninterruptible power supply (UPS)
Current limiter relay
Maximum Power Point Tracker (MPPT)
Voltage regulator
Explanation - MPPT optimizes power output while ensuring charging currents stay within feeder limits.
Correct answer is: Maximum Power Point Tracker (MPPT)
Q.32 32. A distribution system with a ‘high voltage’ level is typically:
Above 33 kV
Between 11 kV and 33 kV
Below 1 kV
Exactly 33 kV
Explanation - High voltage in distribution refers to feeders operating above the standard low-voltage level, often >33 kV.
Correct answer is: Above 33 kV
Q.33 33. Which of the following best describes ‘load balancing’ in a distribution network?
Equalizing the voltage across all phases
Distributing equipment evenly
Shifting loads to off-peak times
Balancing the power factor
Explanation - Load balancing ensures that each phase carries similar current to reduce neutral currents and losses.
Correct answer is: Equalizing the voltage across all phases
Q.34 34. What is the primary function of a 'switchgear' in distribution systems?
Transform voltage levels
Protect and control equipment
Regulate frequency
Measure power factor
Explanation - Switchgear isolates sections, protects equipment, and allows controlled operation of circuit breakers.
Correct answer is: Protect and control equipment
Q.35 35. Which of the following is an example of a distribution network that operates with two parallel feeders?
Radial
Looped
Mesh
Star
Explanation - Mesh configurations have multiple parallel paths between source and load for redundancy.
Correct answer is: Mesh
Q.36 36. The ‘distribution network impedance’ primarily influences which of the following?
Load factor
Voltage drop
Frequency
Power factor
Explanation - Impedance causes voltage losses along the feeder, affecting voltage profiles.
Correct answer is: Voltage drop
Q.37 37. Which protective scheme uses current comparison between primary and secondary sides of a transformer?
Differential relay
Inverse time overcurrent relay
Distance relay
Under-voltage relay
Explanation - Differential relays detect fault currents by comparing currents on each side of the transformer.
Correct answer is: Differential relay
Q.38 38. A typical distribution system outage lasting longer than 6 hours is classified as a:
Minor outage
Major outage
Critical outage
Routine outage
Explanation - Outages are categorized based on duration and impact; >6 hours is generally a major outage.
Correct answer is: Major outage
Q.39 39. Which of the following is a key metric for evaluating distribution network reliability?
System frequency
Average outage time
Voltage regulation
Load factor
Explanation - Average outage time (MTTR) reflects how quickly power is restored after a fault.
Correct answer is: Average outage time
Q.40 40. Which device is used to detect overvoltage conditions in distribution networks?
Undervoltage relay
Surge arrester
Overvoltage relay
Voltage regulator
Explanation - An overvoltage relay trips breakers when voltage exceeds preset limits.
Correct answer is: Overvoltage relay
Q.41 41. The concept of 'phase unbalance' in distribution systems primarily affects:
Neutral current
Load factor
Transformer cooling
System frequency
Explanation - Unbalanced phase loads increase neutral currents and can cause overheating.
Correct answer is: Neutral current
Q.42 42. What is the typical maximum fault current that a low-voltage distribution transformer can handle?
2000 A
500 A
1000 A
5000 A
Explanation - Low-voltage transformers often have fault ratings around 2 kA to withstand short-circuit currents.
Correct answer is: 2000 A
Q.43 43. Which of the following is a major cause of distribution line sag?
Low ambient temperature
High conductor resistance
Low load current
High frequency
Explanation - Sags occur when high resistance conductors carry significant load, causing voltage drop.
Correct answer is: High conductor resistance
Q.44 44. In a distribution network, the ‘load tap changer’ (LTC) is normally used to:
Detect faults
Adjust transformer turns ratio during load changes
Control load shedding
Provide phase balancing
Explanation - LTCs automatically modify tap positions to regulate secondary voltage as load varies.
Correct answer is: Adjust transformer turns ratio during load changes
Q.45 45. Which parameter is NOT typically measured by a distribution monitoring system?
Voltage
Current
Frequency
Water temperature
Explanation - Distribution monitoring focuses on electrical parameters; water temperature is unrelated.
Correct answer is: Water temperature
Q.46 46. The primary advantage of a ‘looped’ distribution system over a radial one is:
Lower installation cost
Higher fault current
Improved reliability through alternative paths
Simpler protection schemes
Explanation - Loops provide alternate paths for power, reducing outage duration when a fault occurs.
Correct answer is: Improved reliability through alternative paths
Q.47 47. What is the effect of installing shunt reactors on a distribution feeder?
Increase voltage levels
Reduce harmonic distortion
Limit capacitive voltage rise
Increase load losses
Explanation - Shunt reactors absorb reactive power, mitigating voltage rise due to capacitors or capacitive loads.
Correct answer is: Limit capacitive voltage rise
Q.48 48. The term 'distribution system reconfiguration' is used to refer to:
Upgrading transformers
Changing network topology to improve performance
Replacing all cables
Installing new metering devices
Explanation - Reconfiguration adjusts the connections between feeders, transformers, and switches for optimal operation.
Correct answer is: Changing network topology to improve performance
Q.49 49. Which of the following is a characteristic of a 'high-availability' distribution system?
Single-point-of-failure design
Redundant feeders and switching devices
Low voltage levels
Minimal monitoring
Explanation - High availability relies on redundancy to maintain service during faults or maintenance.
Correct answer is: Redundant feeders and switching devices
Q.50 50. What does the term 'voltage unbalance factor' (VUF) measure?
The difference between peak and RMS voltage
The ratio of the zero-sequence voltage to the positive-sequence voltage
The imbalance in phase voltages
The harmonic content of voltage
Explanation - VUF quantifies how much the phases differ from the ideal balanced condition.
Correct answer is: The imbalance in phase voltages
Q.51 51. In distribution network fault studies, the 'short-circuit study' determines:
Voltage levels during normal operation
Maximum load capacity
Fault currents and protection settings
Transformer tap positions
Explanation - Short-circuit studies evaluate the magnitude of fault currents for designing protection devices.
Correct answer is: Fault currents and protection settings
Q.52 52. Which device provides instantaneous protection against high fault currents in a distribution system?
Thermal relay
Inverse time overcurrent relay
Fast-acting circuit breaker
Load break switch
Explanation - Fast-acting breakers disconnect the fault immediately, minimizing damage.
Correct answer is: Fast-acting circuit breaker
Q.53 53. The term 'feeders' in distribution systems refers to:
Power plants
Transmission lines
Distribution lines delivering power to loads
Switchgear equipment
Explanation - Feeders carry electricity from substation transformers to end consumers.
Correct answer is: Distribution lines delivering power to loads
Q.54 54. Which type of capacitor bank configuration is typically used for power factor correction in distribution feeders?
Series capacitors
Shunt capacitors
Parallel resistors
Shunt reactors
Explanation - Shunt capacitors provide reactive power locally, improving power factor and voltage.
Correct answer is: Shunt capacitors
Q.55 55. What is the main objective of voltage regulation in distribution networks?
Maintain voltage within acceptable limits during load changes
Increase system frequency
Reduce transformer size
Eliminate harmonic distortion
Explanation - Voltage regulation ensures stable supply voltage for customer equipment.
Correct answer is: Maintain voltage within acceptable limits during load changes
Q.56 56. Which of the following best describes a 'distribution automation system' (DAS)?
A system that monitors weather conditions
A system that controls and monitors distribution equipment automatically
A system that manufactures transformers
A system that schedules power plants
Explanation - DAS uses sensors, RTUs, and SCADA to automate operation of switches, breakers, and other devices.
Correct answer is: A system that controls and monitors distribution equipment automatically
Q.57 57. In a distribution network, which component is most affected by lightning strikes?
Transformers
Capacitor banks
Circuit breakers
Overhead lines
Explanation - Lightning strikes most frequently occur on exposed overhead conductors.
Correct answer is: Overhead lines
Q.58 58. The 'distribution load factor' is calculated by:
Peak load divided by average load
Average load divided by peak load
Total load divided by transformer rating
Transformer rating divided by total load
Explanation - Load factor measures how effectively the system is used relative to its maximum demand.
Correct answer is: Average load divided by peak load
Q.59 59. A 'remote terminal unit' (RTU) is primarily used to:
Measure voltage and current only
Control local equipment based on SCADA commands
Protect against overcurrent
Step up voltage
Explanation - RTUs interface field devices with SCADA, enabling remote operation and data collection.
Correct answer is: Control local equipment based on SCADA commands
Q.60 60. Which type of fault is considered the most severe in a distribution system?
Phase-to-ground
Phase-to-phase
Three-phase
Double line-to-ground
Explanation - Three-phase faults produce the highest fault currents, demanding robust protection.
Correct answer is: Three-phase
Q.61 61. What is the main advantage of a 'smart transformer' compared to a conventional transformer?
Lower cost
Built-in tap changer control and monitoring
Higher voltage rating
Reduced weight
Explanation - Smart transformers incorporate electronics for remote tap control and performance monitoring.
Correct answer is: Built-in tap changer control and monitoring
Q.62 62. In distribution systems, the term ‘distribution line losses’ refers to:
Power lost due to transformer core loss
Power lost due to conductor resistance and reactance
Power lost in capacitors
Power lost in switchgear
Explanation - Line losses arise from I²R heating and reactive losses in the conductors.
Correct answer is: Power lost due to conductor resistance and reactance
Q.63 63. Which of the following is a benefit of using underground cables in distribution?
Higher voltage ratings
Lower installation costs
Improved aesthetics and lower lightning risk
Higher fault currents
Explanation - Underground cables reduce visual impact and are shielded from lightning, but are more expensive.
Correct answer is: Improved aesthetics and lower lightning risk
Q.64 64. The primary purpose of a 'static VAR compensator' (SVC) in a distribution network is to:
Step up voltage
Reduce harmonic distortion
Provide dynamic reactive power support
Control power factor of loads
Explanation - SVCs rapidly adjust reactive power to maintain voltage stability during load changes.
Correct answer is: Provide dynamic reactive power support
Q.65 65. In a distribution system, the 'fault level' is expressed in terms of:
Voltage
Current
Power
Frequency
Explanation - Fault level is the maximum current that can flow during a fault, used for protection design.
Correct answer is: Current
Q.66 66. Which type of protection scheme is most suitable for a long feeder with high impedance?
Distance protection
Inverse time overcurrent protection
Under-voltage protection
Differential protection
Explanation - Distance relays measure fault impedance, making them effective on long, high-impedance feeders.
Correct answer is: Distance protection
Q.67 67. What is the main function of a 'distribution substation'?
Generate electricity
Transform voltage from high to low for local distribution
Store electricity
Distribute power to transmission lines
Explanation - Substations step down voltage from transmission levels to distribution voltages.
Correct answer is: Transform voltage from high to low for local distribution
Q.68 68. In distribution network planning, 'load forecasting' is used to:
Determine the required transformer capacity
Predict weather patterns
Calculate system frequency
Measure line losses
Explanation - Load forecasts predict future demand, guiding sizing of transformers and feeders.
Correct answer is: Determine the required transformer capacity
Q.69 69. Which of the following is a typical characteristic of an underground distribution cable?
Higher dielectric strength
Higher voltage rating
Higher thermal conductivity
Lower cost than overhead lines
Explanation - Underground cables have superior dielectric properties, allowing operation at higher voltages.
Correct answer is: Higher dielectric strength
Q.70 70. What role does the 'grounding electrode' play in a distribution system?
Increase system voltage
Provide a low-impedance path for fault currents
Serve as a voltage source
Reduce harmonic distortion
Explanation - Ground electrodes safely dissipate fault currents into earth, protecting equipment and personnel.
Correct answer is: Provide a low-impedance path for fault currents
Q.71 71. Which device is commonly used to control the opening of a distribution feeder during a fault?
Circuit breaker
Capacitor bank
Switching relay
Voltage regulator
Explanation - Circuit breakers interrupt fault currents, isolating the affected portion of the network.
Correct answer is: Circuit breaker
Q.72 72. In distribution systems, a 'tap changer' that can be operated from the secondary side of a transformer is called:
Primary tap changer
Secondary tap changer
Shunt tap changer
On-load tap changer
Explanation - Secondary tap changers adjust the tap position from the low-voltage side without interrupting load.
Correct answer is: Secondary tap changer
Q.73 73. The 'distribution network harmonic distortion' is mainly caused by:
Resistive loads
Non-linear loads
Transformer cores
Neutral grounding
Explanation - Devices like UPS and power electronics draw non-sinusoidal currents, generating harmonics.
Correct answer is: Non-linear loads
Q.74 74. What is the purpose of a 'fault current limiter' in a distribution feeder?
Limit the maximum fault current to protect downstream equipment
Increase system voltage during faults
Regulate power factor
Control load shedding
Explanation - Fault current limiters reduce the magnitude of fault currents to safe levels.
Correct answer is: Limit the maximum fault current to protect downstream equipment
Q.75 75. In a distribution system, the term 'distribution voltage drop' refers to:
The difference between nominal and actual voltage at the consumer
The variation in voltage during a fault
The maximum voltage the transformer can handle
The change in voltage across a transformer secondary
Explanation - Voltage drop is the loss of voltage along the feeder from substation to end customer.
Correct answer is: The difference between nominal and actual voltage at the consumer
Q.76 76. Which of the following is NOT a typical component of a distribution feeder?
Transformers
Switches
Cables
Generators
Explanation - Generators are part of power generation; distribution feeders deliver power, not generate it.
Correct answer is: Generators
Q.77 77. The main benefit of installing a 'remote monitoring system' in a distribution network is:
Immediate visual inspection of cables
Real-time fault detection and status reporting
Manual operation of switches
Physical protection of equipment
Explanation - Remote monitoring provides instant alerts on faults, enhancing response times.
Correct answer is: Real-time fault detection and status reporting
Q.78 78. Which of the following is a common protection device used for phase-to-ground faults?
Ground fault relay
Overcurrent relay
Voltage transformer
Capacitor bank
Explanation - Ground fault relays detect abnormal currents to earth and trip breakers.
Correct answer is: Ground fault relay
Q.79 79. In a distribution network, what is the effect of increasing the number of capacitors on line voltage?
Voltage decreases
Voltage increases
Voltage remains unchanged
Voltage oscillates
Explanation - Adding capacitors supplies reactive power, raising line voltage toward the nominal value.
Correct answer is: Voltage increases
Q.80 80. Which of the following is a typical application of a 'dynamic voltage regulator' (DVR) in a distribution system?
Step up voltage during transmission
Maintain voltage stability during load swings
Measure current
Protect against overcurrent
Explanation - DVRs adjust tap positions in real time to keep voltage within limits amid varying loads.
Correct answer is: Maintain voltage stability during load swings
Q.81 81. The 'distribution network load curve' is used to:
Plot voltage over time
Show load variation throughout the day
Measure transformer temperature
Calculate fault currents
Explanation - Load curves illustrate how demand changes, aiding planning and operation.
Correct answer is: Show load variation throughout the day
Q.82 82. In a radial distribution system, the point where the transformer is connected to the feeder is called the:
Primary node
Feeder head
Load point
Terminal bus
Explanation - The feeder head is the starting point of the feeder from the substation transformer.
Correct answer is: Feeder head
Q.83 83. What is the purpose of a 'load break switch' in a distribution network?
Connect and disconnect circuits while under load
Regulate voltage
Measure current
Limit fault currents
Explanation - Load break switches can safely open/close live circuits, allowing maintenance without outage.
Correct answer is: Connect and disconnect circuits while under load
Q.84 84. Which of the following factors most significantly influences the voltage drop in a distribution feeder?
Conductor material
Ambient temperature
Load current
Transformer rating
Explanation - Higher currents increase I²R losses, leading to greater voltage drop.
Correct answer is: Load current
Q.85 85. The 'distribution network voltage flicker' is caused by:
High reactive power demand
Fast voltage fluctuations due to large load changes
Ground fault
Transformer core loss
Explanation - Flicker arises from rapid voltage variations caused by industrial motors or large loads turning on/off.
Correct answer is: Fast voltage fluctuations due to large load changes
Q.86 86. Which of the following best describes a ‘distribution substation’ function during peak demand?
Generate additional power
Step down voltage and supply load
Store energy in batteries
Reduce transmission losses
Explanation - During peak, substations deliver the required lower-voltage power to the distribution network.
Correct answer is: Step down voltage and supply load
Q.87 87. In a distribution network, the term 'feeder loop' refers to:
A single line running from substation to consumer
Two parallel lines with an interconnection forming a loop
A cable buried underground
A set of transformers in series
Explanation - A feeder loop provides alternate paths for power flow, enhancing reliability.
Correct answer is: Two parallel lines with an interconnection forming a loop
Q.88 88. Which device is used to measure the amount of reactive power supplied by a capacitor bank in a distribution feeder?
Power factor meter
Current transformer
Voltage transformer
Shunt reactor
Explanation - A power factor meter quantifies the ratio of real to apparent power, indicating reactive power contribution.
Correct answer is: Power factor meter
Q.89 89. The 'maximum allowable voltage rise' in a distribution feeder is typically limited to:
5%
10%
15%
20%
Explanation - Standards often set a 5% maximum rise to ensure voltage quality for customers.
Correct answer is: 5%
Q.90 90. In distribution network reconfiguration, a common objective is to:
Reduce the number of transformers
Minimize the length of feeders
Maximize power losses
Eliminate all fault currents
Explanation - Shorter feeders reduce voltage drop and losses, improving system performance.
Correct answer is: Minimize the length of feeders
Q.91 91. Which of the following is a key parameter for designing a distribution circuit breaker?
Maximum load current
Frequency
Transformers' core material
Ambient temperature only
Explanation - Circuit breakers must handle the highest expected load current without failure.
Correct answer is: Maximum load current
Q.92 92. The 'distribution network outage probability' is used in:
Load forecasting
Reliability assessment
Voltage regulation
Transformer sizing
Explanation - Outage probability quantifies the likelihood of service interruptions in the network.
Correct answer is: Reliability assessment
Q.93 93. In a distribution system, which parameter directly affects the fault current magnitude?
Load factor
Transformer impedance
Line length
Voltage rating
Explanation - Lower transformer impedance allows higher fault currents, influencing protection settings.
Correct answer is: Transformer impedance
Q.94 94. The use of ‘dynamic line rating’ in distribution feeders helps to:
Increase transformer capacity
Adjust load factor
Accurately assess current carrying capacity based on weather conditions
Improve voltage regulation
Explanation - Dynamic rating adjusts allowed current based on temperature, wind, and ambient factors.
Correct answer is: Accurately assess current carrying capacity based on weather conditions
Q.95 95. In a distribution network, the 'ground fault loop impedance' is:
Impedance of the grounding electrode only
Impedance of the faulted conductor only
Sum of fault conductor, feeder, and grounding electrode impedances
None of the above
Explanation - Ground fault loop impedance determines the fault current magnitude.
Correct answer is: Sum of fault conductor, feeder, and grounding electrode impedances
Q.96 96. The purpose of a 'phase angle relay' in distribution systems is to:
Detect overcurrent
Measure voltage magnitude
Detect phase angle differences for fault detection
Control transformer tap settings
Explanation - Phase angle relays compare phase angles to identify fault conditions.
Correct answer is: Detect phase angle differences for fault detection
Q.97 97. In distribution networks, the ‘minimum fault current’ is significant because it:
Determines transformer size
Sets the lowest protection threshold
Limits load factor
Influences voltage regulation
Explanation - Protection devices must detect and isolate faults that produce at least the minimum fault current.
Correct answer is: Sets the lowest protection threshold
Q.98 98. Which of the following best describes a 'distribution system' in power engineering?
Network delivering power from generators to consumers
Transmission line connecting two countries
The generation unit of a power plant
A storage facility for energy
Explanation - Distribution systems carry power from substations to end users at low voltages.
Correct answer is: Network delivering power from generators to consumers
Q.99 99. The main reason for using ‘grounded star’ connection in distribution networks is:
To increase system frequency
To provide a reference point and safety grounding
To step up voltage
To reduce line losses
Explanation - Grounded star connects neutral to earth, offering a safe return path for fault currents.
Correct answer is: To provide a reference point and safety grounding
Q.100 100. In the context of distribution systems, what does the abbreviation 'DSI' stand for?
Distribution System Integration
Distribution Service Interface
Distribution System Improvement
Distribution Service Indicator
Explanation - DSI commonly refers to Distribution Service Indicator, a device showing supply status to consumers.
Correct answer is: Distribution Service Indicator