Aktu Power System – I KEE-501 Btech Short Question Quantum Book Pdf

Learn about Power System – I Short Question Notes from the B.Tech. AKTU Quantum Book. Learn about the concepts of power generation, transmission, and distribution for effective and dependable electrical systems.

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Unit-I: Power Generation (Short Question)

Q1. What are the functions of dam ?

Ans.

• 1. In a hydroelectric project, the dam’s purpose is to produce an artificial head and storage.
• 2. It changes the direction of the water flow so that it can be used to create electricity.
• 3. It is a hydro project’s most costly and crucial component.
• 4. Site topography, geological characteristics, subsoil conditions, and other factors all have a role in the sort of dam that is most suited for a certain location.

Q2. Draw the functional block diagram representation of steam power plants.  

Ans. 

Q3. What are the problems associated in development of hydropower ?

Ans.

• 1. Huge financial requirements. 
• 2. Land acquisition. 
• 3. Technical problems. 
• 4. Skilled manpower and labour problems.  

Q4. Name the main parts of a nuclear reactor. 

Ans. 1. Fuel                                                     2. Reactor core

3. Moderator                                                    4. Shielding

5. Control rods                                                 6. Reflector

7. Coolant                                                        8. Reactor vessel

Q5. What is load duration curve ? 

Ans. 1. A load duration curve shows the chronological load curve’s load elements rearranged in descending order of magnitude. The historical load curve served as the basis for this curve.

2. The load duration curve provides a clear insight of the economics of power generation. It becomes simpler to choose base load and peak load power plants properly.

Q6. What do you understand by demand factor ? 

Ans. The demand factor is the ratio of the system’s real maximum demand to its overall connected load.  

Q7. Define load factor.

Ans. The ratio of the average load over a specific time period to the peak load experienced during that time is the load factor of a system. 

Q8. Explain base load.

Ans. 

• 1. The base load is the amount of power that is supplied 100% of the time and below which demand never decreases.
• 2. The base load plants are substantially loaded since continuous operation at high load factors increases these plants’ capacity factors, making the operation of expensive plants an economic proposition.
• 3. If it is possible to maintain low operating expenses, a high capital cost is acceptable.

Q9. Define diversity factor. 

Ans. The diversity factor is the ratio of the total maximum demands of all system subdivisions to the total maximum demand. 

Diversity factor 

Q10. What do you understand by economizer ? 

Ans. A device known as an economizer uses the waste heat from the flue gases to warm the feed water.

Q11. Write the advantages of hydro electric power plant.  

Ans.

• 1. No fuel charges. 
• 2. Highly reliable. 
• 3. Low maintenance and operation charges. 
• 4. Low running cost. 
• 5. No standby losses. 

Q12. Give the advantages and disadvantages of a nuclear power plant.

Ans. A. Advantages: 

• 1. Compared to other conventional power plants of the same capacity, nuclear power plants use less area.
• 2. Nuclear power facilities are capable of supplying significant amounts of energy. They function best when the load factor is high (80 to 90%).

B. Disadvantages: 

• 1. Nuclear power plants always have substantial capital costs.
• 2. The working conditions at nuclear power plants are always bad for employees’ health.

Unit-II: Transmission and Distribution of Electric Power-I (Short Question)

Q1. What is single line diagram of power system ?

Ans. The components of a power system are more simply shown in a single line diagram, where each component is denoted by a symbol.  

Q2. Draw single line diagram of a typical power system.  

Ans. 

Q3. Draw the symbols of various components of a power system which are used in single-line diagram representation. 

Ans. 

Q4. Explain the following components of distribution power system: 

i. Feederr 

ii. Service mains.

Ans. i. Feeder: A feeder is a conduit that joins the sub-stations to the distribution hub for power. 

ii Service mains: A service mains is a brief connection that joins the consumer terminals to the distributor. 

Q5. How does isolator differ from circuit breaker? 

Ans. 

Q6. Draw and explain 3-wire DC system.

Ans. As shown in Fig., a 3-wire DC system consists of two outer wires and a central, or neutral, wire that is grounded at the generator end. If the load is balanced, there is no current flowing through the neutral wire.

Q7. Define skin effect. 

OR

What is meant by skin effect ? 

Ans. 1. The skin effect is the propensity for alternating current to concentrate close to a conductor’s surface.

2. The conductor’s effective cross-sectional area through which current flows is less as a result of the skin effect. As a result, when a conductor is carrying alternating current, its resistance marginally increases.

Q8. What is proximity effect ?

Ans. The proximity effect is the result of inductance, which affects how current is distributed in a conductor when there are other conductors nearby.  

Q9. What is the need for stranding the conductors ? 

Ans. 1. The stranded conductor is sufficiently flexible, making it appropriate to be wound up easily for long distance transportation.

2. The flexibility of a stranded conductor rises as the number of strands increases for a conductor with the same cross-sectional area.

Q10. What are the components of transmission line ? 

Ans. 1. Conductors 

2. Insulators 

3. Supports/ towers. 

Q11. Define term corona.

Ans. Corona is the term for the occurrence of a violet glow, hissing sound and ozone gas production in an overhead gearbox line.

Q12. Define critical disruptive voltage and visual critical voltage. 

Ans. Critical disruptive voltage: It is to neutral defined as the minimum phase voltage at which corona occurs. It is denoted by V_c or V_do,

Visual critical voltage: It is the minimum phase to neutral voltage at which corona glow appears all along the line. It is denoted by V_vo.

Q13. What is the Ferranti effect ?

Ans. The Ferranti effect is a phenomenon that causes a voltage increase at the line’s receiving end when it is open-circuited or lightly loaded.  

Q14. Which factors affect corona ?

Ans.

• 1. Conductor surface gradient. 
• 2. Condition of conductor surface. 
• 3. Atmospheric conditions. 
• 4. Air density factor. 

Q15. How a circuit breaker is specifically different from a switch? 

Ans. 

Q16. State the empirical formula for determining the system voltage of transmission line. 

Ans. To calculate the best voltage lines longer than 30 km, an empirical formula is used.

The empirical formula is, 

where, V = Transmission voltage (kV)

L = Distance ef transmission line in km  

Q17. What are ACSR conductor stands? 

Ans. ACSR (Aluminium Conductor Steel Reinforced): It has an aluminium layer surrounding a steel layer that serves as the central layer of the stranded conductor. A cross-section of an ACSR conductor is shown in Fig.

Q18. What are the various factors affecting choice of transmission voltage level ? 

Ans. 1. Power to be transmitted 

2. Distance of transmission line.  

Q19. State Kelvin’s law for size of conductor for transmission.  

Ans. The most economical area of conductor is that for which the total cost of transmission line is minimum. This is known as Kelvin’s law. 

Q20. What is dielectric strength of air ? 

Ans. Air has a dielectric constant of about 3 kV/mm. Its precise value changes depending on the size and form of the electrodes and rises as air pressure increases. 

Q21. Draw single line diagram of power system network from generation to distribution showing all the voltage levels at various intermediate stages. 

Ans. 

Q22. Why receiving end voltage appears high compared to sending end voltage in case of lightly loaded transmission lines ?

Ans. With low loads, the charging current in the line causes a voltage drop that is in phase opposition to the receiving end, causing the receiving end voltage to be greater than the sending end voltage.

Unit-III: Transmission and Distribution of Electric Power-II (Short Question)

Q1. Define sag in transmission line. 

Ans. Sag is the term used to describe the difference in levels between the conductor’s point of support and its lowest point.

Q2. Describe the vibrations of power conductor and explain the method used to damp out these vibrations.  

Ans. Vibration of power conductor: 

A. Aeoline vibrations: The amplitudes of the Aeoline vibrations range from 2 to 5 cm, with a frequency range of 5 to 50 Hz. As a result, these vibrations have a high frequency but a low amplitude. Such vibrations can be produced by winds with speeds between 2 and 40 kmph. 

a. Minimization of aeoline vibration: 

• i. Use of bundle conductor 
• ii. Proper design and location of spacers 
• iii.. Use of damper 
• iv. Use of clamps.  

B. Galloping of conductors/dancing of conductors: The term “galloping” refers to the low frequency, high amplitude dancing of conductors. These are the oscillations across the entire conductor range.

b. Minimization of galloping of conductors: 

There is no way to stop a horse from galloping. Nonetheless, in icing situations, the height of the conductors can be correctly built taking into account the potential amplitude of galloping.

Q3. What are the factors affecting the sag in a transmission line ? 

Ans.

• 1. Weight of conductor 
• 2. Span length (distance between the poles) 
• 3. Working tensile strength 
• 4. Ice coating 
• 5. Wind pressure and temperature.

Q4. What is the effect of wind and ice on sag ? 

Ans. The mechanical stress in the conductor increases as a result of the weight of ice deposits on the line and the pressure of the wind; hence, the line needs to be built to handle these stresses and tensions.

Q5. Why is it disadvantageous to provide either too high sag or too low sag ?  

Ans. 1. If the sag is too significant, additional conductor material will be needed, more weight will need to be supported by the supports, higher supports will be required, and there is a probability that the swing-amplitude will be higher owing to wind load.

2. If the sag is too low, the conductor is under more tension and is therefore more likely to break under extra stress, such as that caused by line vibration or a drop in temperature.

Q6. What are the methods used for equalizing the potential across the insulator string in transmission lines ?

Ans. 1. Use of long cross arms. 

2. Capacitance grading or grading of units. 

3. Use of guard rings. 

Q7. What is failure of insulator ?

Ans. Between the line conductors and the supports, the insulators provide the necessary insulation, preventing any leakage current from the conductor to the ground. Insulator failure occurs when it does not succeed in doing so.

Q8. How are the causes of failure of insulators ?

Ans.

• 1. Cracking of porcelain
• 2. Porosity
• 3. Puncture 
• 4. Mechanical stresses
• 5. Flash-over. 

Q9. What is string efficiency ?

Ans. The ratio of the voltage across the entire string to the product of the number of units and the voltage across the unit closest to the line conductor is known as the string efficiency.

where, n = Number of units.

Q10. What is the significance of string efficiency ?  

Ans. Greater string effectiveness a more even distribution of voltage across the suspension insulator.

Q11. What are the types of insulators used in transmission and distribution? 

Ans.

• 1. Pintype 
• 2. Suspension type 
• 3. Strain insulator 
• 4. Shackle insulator 
• 5. Stay insulator.

Q12. How are voltage distribution and the string efficiency affected by rain ? 

Ans. Insulators become moist during the rainy season, increasing the mutual capacitance value. As a result, k, the ratio of shunt to mutual capacitance, drops. This makes the voltage distribution more uniform. Hence, string efficiency is higher during the rainy season. 

Unit-IV: Transmission Line Parameters (Short Question)

Q1. What is transposition of transmission line ? 

Ans. 1. By transposition of line conductors, we imply moving the three phases twice along the length of the line’s supports.

2. In actual fact, the conductors are arranged so that one-third of the line is covered by each of the three conceivable configurations.

Q2. What is the need of transposition of transmission lines ?

Ans. 1. It lessens the three phases’ electrostatic imbalance. Voltage imbalance is also stabilized using it.

2. Line transposition arrangements aid in lowering system power loss.

Q3. Why is leakage conductance negligible in overhead lines ? 

Ans. Leakage currents that pass insulators and air are what cause the leakage conductance. Leakage conductance in overhead wires is little because leakage current, which is much smaller than nominal current, is typically disregarded.

Q4. For determination of inductance of a circuit, determination of flux linkages is essential. Why ?

Ans. 1. Magnetic lines form concentric circles around a conductor that carries current. In an AC system, the field that is formed up around the conductor changes and links with other conductors as well as the same conductor.

2. The line has inductance, which is the number of flux linkages per unit current, as a result of these flux linkages. Hence, figuring out the flux connections is crucial for figuring out a circuit’s inductance.

Q5. Why the effect of ground on the line capacitance can be neglected?  

Ans. Because the height of conductors is greater than the distance between them, the influence of ground on the line capacitance is extremely little.

Q6. For what purpose bundle conductor are used in transmission line. 

OR

Write advantages of bundled conductor. 

Ans. 1. Reduced corona loss. 

2. Reduced radio interference. 

3. Lower surge impedance. 

Q7. What are the factors which govern the performance of a transmission line ? 

Ans. Series resistance R, inductance L, shunt capacitance C and conductance G. 

Q8. What is the effect of ground on the capacitance of a transmission line? 

Ans. A transmission line’s capacitance is slightly increased by the presence of ground.

Q9. An ACSR conductor having a diameter of 1 cm has an internal inductance equal to 0.05 mH/km. If it is replaced by another ACSR having a diameter of 2 cm, then calculate its internal inductance. 

Ans. Given: L= 0,05 mH/km, d₁ = 1 cm= D₁, d₂ = 2 cm D₂

To Find: Internal inductance 

Q10. What do you understand by mutual-GMD 7 

Ans. The geometric mean of the separation between two conductors is known as the mutual-GMD. It merely displays the corresponding geometric spacing.

Q11. Discuss the effect of change in temperature on length of overhead transmission line. 

Ans. 1. As the temperature changes, the conductor’s length will as well.

2. When stringing the line at the time of erection, the impact of this should be taken into account.

3. If a is the linear coefficient of thermal expansion and if the temperature changes from t₁ to t₂, the length l₂ at temperature t₂ is given by

4. The value of a should be that at t₁. 

5. If the temperature is increased, the length of the conductor is increased. 

Unit-V: Insulated Cables (Short Question)

Q1. What is general construction of cable ?

Ans. 

Q2. Give classification of underground cables.

Ans.

• 1. Low voltage (LT) cables. 
• 2. High voltage (HIT) cables. 
• 3. Super-tension (ST) cables. 
• 4. Extra high tension (EHT) cables.
• 5. Extra super-voltage cables. 

Q3. Write the expression of insulation resistance of a single core cable.

Ans. Insulation resistance of a single-core cable is given by

Q4. On what factors does the insulation resistance of a cable depend ?

Ans. The core radius, insulation thickness, cable length, and the resistivity of the insulating material all affect a cable’s insulation resistance. 

Q5. What is grading of cable ? Why is it necessary ?

Ans. A. Grading of cables: Grading of cables refers to the process of achieving a uniform distribution of stress in cable insulation. 

B. Necessity: Due to the following two negative effects of an uneven distribution, cables are graded:

• i. More insulating thickness is needed, increasing the size and expense.
• ii. It might cause insulation to deteriorate.

Q6. Write the limitations of grading.  

Ans. 1. During the service life of the cable, the permittivities of the layers may not remain constant in capacitance grading. As a result, at the typical working voltage, the stress distribution may alter and might possibly result in insulation breakdown.

2. Because they are so thin, the intersheaths are susceptible to breakage during transit or installation. The charging current of lengthy cable lines cannot be carried by the narrow intersheaths, which reduces the current carrying capability.

Q7. What is the mechanism of breakdown of an underground cable ?

Ans. There are two way in which breakdown of cables usually occurs : 

• 1. One method involves a coring and tracking progression that always begins at the core or sheath and eventually bridges the electrons.
• 2. Thermal instability is another method, which happens when the power factor increases quickly as the temperature rises.

Q8. What are the main reasons of power loss that occurs in the dielectric of a cable?

Ans. 1. Conductivity of insulation. 

2. Dielectric hysteresis or dielectric absorption. 

3. Ionization or corona.

Q9. Name the sources of heat generation in cables. 

Ans. 1. I²R losses in the conductor. 

2. Dielectric losses in the cable insulation. 

3. Losses in the metallic sheath and armourings. 

Q10. Mention important factors to be considered while selecting a cable.  

Ans. Continuous current rating, voltage grade, allowed voltage drop, short circuit rating (only for HT cables), and operational cost are things to take into account when choosing a cable.

Q11. Write any two characteristics of insulating material.  

Ans. 1. Its insulation resistance needs to be extremely strong in order to prevent leakage current.

2 Its dielectric strength must be extremely strong to prevent electrical breakdown.

Q12. What is the range of surge impedance in case of underground cable?

Ans. Range of surge impedance is 40 to 60 𝛀.  

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