Transmission and Distribution Systems MCQs (Part-8)
What is the primary cause of power loss in transmission lines?
A Voltage
B Impedance
C Resistance
D Frequency
Power loss in transmission lines is primarily caused by resistance, which converts some of the electrical energy into heat. The loss is proportional to the square of the current, and higher resistance results in greater power dissipation.
Which method is commonly used to reduce power loss in transmission systems?
A Increasing voltage
B Using thick conductors
C Using higher current
D Reducing impedance
Power loss in transmission systems is reduced by increasing the voltage. Higher voltage allows for lower current, which reduces resistive losses in the transmission lines. This is why high‐voltage transmission is commonly used for long‐distance power distribution.
What is the role of load balancing in a power distribution system?
A Control voltage
B Minimize energy loss
C Maintain frequency
D Equalize power flow
Load balancing ensures that power is distributed evenly across the system, preventing overloading of any single circuit. It helps in maintaining stable operation, reducing losses, and improving the efficiency of the distribution network.
Which factor has the most significant impact on power quality in an electrical system?
A Load demand
B Voltage fluctuations
C Insulation material
D Frequency
Voltage fluctuations, including dips and surges, significantly affect power quality. These fluctuations can cause electrical equipment to malfunction or fail. Proper voltage regulation and control are essential to maintaining stable power quality in distribution systems.
What is the primary purpose of reactive power in a power system?
A Maintain voltage stability
B Increase current flow
C Increase power loss
D Reduce resistance
Reactive power is crucial for maintaining voltage levels across the power system. It helps ensure that there is enough power to sustain the voltage needed for electrical equipment to function properly, preventing voltage instability and system collapse.
What does the term “power factor” refer to in electrical systems?
A Frequency of current
B Ratio of voltage to current
C Ratio of real power to apparent power
D Efficiency of power transmission
Power factor is the ratio of real power (useful power) to apparent power (total power supplied by the source). A power factor close to 1 indicates efficient energy use, while a low power factor signifies inefficiency and potential for increased losses.
What is the effect of high power factor on a transmission system?
A Increases losses
B Decreases losses
C Increases current
D Increases voltage
A high power factor indicates efficient use of electrical power, where most of the supplied power is converted into useful work. This reduces the losses in the system and minimizes the need for reactive power, improving overall efficiency.
What is the most common method for balancing load in a power distribution network?
A Load shifting
B Capacitor banks
C Power factor correction
D Transformer tap‐changing
Transformer tap‐changing is commonly used to balance loads in a power distribution network. It adjusts the voltage output from transformers to match the changing load demands, ensuring that the system operates efficiently and without overloading.
What is the impact of poor power quality on electrical equipment?
A Improved efficiency
B Increased voltage
C Reduced lifespan
D Stable performance
Poor power quality, including voltage fluctuations, harmonics, and unbalanced loads, can cause damage to electrical equipment. This leads to premature failure, higher maintenance costs, and reduced operational lifespan of machines and devices.
What does a harmonic filter do in a power distribution system?
A Removes harmonics
B Stabilizes frequency
C Increases current flow
D Reduces voltage spikes
A harmonic filter is used to remove harmonics from the power system. Harmonics are unwanted frequencies that distort the voltage and current waveforms. Harmonic filters improve power quality and protect equipment from the damaging effects of harmonics.
How does the use of high‐voltage transmission reduce power losses?
A Increases power flow
B Reduces impedance
C Reduces current
D Increases current
By increasing the voltage for transmission, the current is reduced for the same power transfer. Since power loss is proportional to the square of the current (I²R), reducing the current significantly lowers power loss in the transmission lines.
What is one of the main challenges in maintaining power quality in large electrical systems?
A Load imbalance
B High power factor
C Frequency stability
D Voltage dips
Voltage dips, also known as sags, occur when the voltage level temporarily drops below the normal range. These dips can disrupt equipment operation, cause machinery malfunctions, and degrade overall power quality, especially in large systems.
What is the effect of an unbalanced load on a power system?
A Reduced voltage
B Increased energy loss
C Increased power factor
D Improved efficiency
An unbalanced load in a power system results in unequal distribution of current, causing increased losses due to uneven heating of conductors. This inefficiency leads to higher operational costs and potential overheating of equipment.
What is one way to improve power quality in a system?
A Reduce load
B High resistance cables
C Power factor correction
D Use of capacitors
Power factor correction improves the efficiency of the power system by aligning the current and voltage waveforms, reducing losses, and ensuring that the maximum amount of electrical power is used for work rather than for generating reactive power.
What is the role of energy‐efficient transformers in reducing power losses?
A Lower energy consumption
B Improve power factor
C Increase voltage
D Reduce current
Energy‐efficient transformers are designed to minimize losses during the voltage conversion process. By using higher‐quality materials and advanced design, these transformers reduce the amount of wasted energy, thus lowering the overall energy consumption of the system.