Power Systems MCQ Set 1
1. Bundled conductors used in the EHV transmission lines result into ____
a) reduced inductance
b) increase capacitance
c) increase inductance
d) increase resistance
Answer
Answer: a [Reason:] Bundled conductors cause the GMR to increase and thus reducing the inductance.
2. The fictitious resistance, “ r’ ” implemented in the conductors for the calculation of the inductance is _______
a) 0.7788r
b) 2r
c) r/0.7788
d) r
Answer
Answer: a [Reason:] It is 0.7788r in the equivalent network configuration.
3. (i) Skin effect
(ii) Proximity effect
Which of the options are right?
a) Both (i) and (ii) cause non uniform distribution of the current
b) Neither (i) and (ii) cause non uniform distribution of the current
c) Both (i) and (ii) cause uniform distribution of the current
d) Only (i) causes the non uniformity of the current
Answer
Answer: a [Reason:] Skin-effect as well as the Proximity effect cause the non distribution of the flux linkages, leading to non uniform distribution of the current.
4. Ferranti effect causes the non uniform distribution of the current and voltage.
a) True
b) False
Answer
Answer: b [Reason:] Only the voltage regulation is affected due to the Ferranti law.
5. Apart from the skin effect the phenomena which cause/s the non uniform distribution of the current is ______
a) Proximity effect
b) Faraday’s effect
c) Ferranti effect
d) All of the mentioned
Answer
Answer: a [Reason:] Only the proximity effect and skin effect cause the non uniform distribution of the current.
6. Bundle conductor ______ inductance and ______ capacitance of a transmission line.
a) reduces, increases
b) increases, reduces
c) reduces, keeps constant
d) keeps constant, increases
Answer
Answer: a [Reason:] The inductance reduces by employing the bundle conductor.
7. For a transmission line, the distributed parameters is/are ______
a) Resistance, inductance, capacitance
b) Resistance
c) Inductance, capacitance
d) None of the mentioned
Answer
Answer: a [Reason:] All R, L and C are considered distributed parameters.
8. As the frequency increases, the flux inside the conductor will ________
a) decrease
b) increase
c) be constant
d) be zero
Answer
Answer: a [Reason:] Skin effect is inversely proportional to frequency.
9. Self GMD and GMR vary with each other as ____
a) linearly
b) parabolic
c) exponential
d) none of the mentioned
Answer
Answer: d [Reason:] Because the self GMD and GMR are same quantities.
10. If the diameter of the conductor is increased then _______
a) inductance increases
b) inductance remains unaltered
c) inductance decreases
d) inductance can’s be determined
Answer
Answer: a [Reason:] Inductance will increase.
Power Systems MCQ Set 2
1. Effect of earth is considered insignificant while calculating the inductance of a single phase transmission line.
a) True
b) False
Answer
Answer: a [Reason:] The earth’s magnetic symmetry does not affect the inductance of the line.
2. Effect of earth’s presence on the magnetic field geometry is _____
a) significant
b) insignificant
c) cannot be said
d) none of the mentioned
Answer
Answer: a [Reason:] This is because the relative permeability of earth is about the same as that of air and its electrical conductivity is relatively small.
3. The inductance of the transmission line is do not contain effect of earth electric field geometry while the capacitances contain.
a) True
b) False
Answer
Answer: a [Reason:] It is true as the earth’s magnetic field symmetry is insignificant to the inductance while the electric field symmetry is.
4. The end effect information is included in the inductance of a transmission line.
a) True
b) False
Answer
Answer: b [Reason:] Since TL is infinitely long, the end effects are ignored and they are not a part of the inductance formula.
5. The number of the strands included in the stranded cables while implementing a similar cable equivalent of single strand should be ________
a) 3x2-3x+1
b) 2x2-3x+1
c) 3x2-2x+1
d) 3x2-x+1
Answer
Answer: a [Reason:] It is 3x2-3x+1.
6. The overall diameter of a stranded conductor if ‘x’ is the number of layers and each layer has a diameter ‘d’ will be
a) (2x-1)d
b) (3x-1)d
c) (6x-3)d
d) (2x+1)d
Answer
Answer: a [Reason:] It is given by (2x-1)d.
7. _______ conductors are the latest trend of the extra high voltage lines.
a) Bundled
b) Parallel
c) ACSR
d) Bundled or ACSR
Answer
Answer: a [Reason:] The bundled ACSR conductors have corona free characteristics and they have good tensile strength.
8. A 10 MVA, 11 kV alternator has positive, negative and zero sequence reactance of 25%, 40%,10% respectively. The resistance that must be placed in the neutral such that zero sequence of fault current for a single phase to ground fault will not exceed the rated line current in ohms is
a) 2.66 Ω
b) 1.66 Ω
c) 12.1 Ω
d) 0.22 Ω
Answer
Answer: a [Reason:]
Power Systems MCQ Set 3
1. Which of the following material is not used for overhead line insulators?
a) Porcelain
b) Glass
c) PVC
d) Steatite
Answer
Answer: c [Reason:] In addition to high insulation resistance and high relative permittivity, overhead line insulators must have high mechanical strength to bear the weight of line insulators, wind stress and ice loading if any. PVC have good insulation resistance but it does not have such mechanical strength so it is not suitable for overhead line insulators.
2. Pin type insulator are mostly subjected to which type of mechanical stress?
a) Compressive stress
b) Tensile stress
c) Both tensile and compressive stress
d) Twisting stress
Answer
Answer: d [Reason:] The conductor is placed in the governor at the top of the insulator and is tied down. So the weight of wire acts on the top of the insulator in downward direction causing compressive stress on insulator. No tensile stress is acted on the pin type insulator.
3. Which of the following is the main field of application of pin type insulator?
a) Distribution system
b) Transmission system
c) Transmission and distribution system
d) EHV transmission system
Answer
Answer: a [Reason:] Pin type insulator become very bulky and cumbersome when designed for higher voltage. Pin insulators beyond 50,000 Volts becomes uneconomical. the modern practice is not to use pin type insulator SBI on 33kv so use of pin insulator is limited to distribution level voltage.
4. Suspension type insulator are subjected to ________
a) tensile stress
b) compressive stress
c) tensile and compressive stress
d) depends on its use
Answer
Answer: a [Reason:] Suspension type insulator hangs from the cross arms of the suspending supporting structure. The line conductor is attached to its lower end hence the load of the conductor causes tensile stress on the suspension insulator.
5. A transmission line consists of 9 discs of suspension insulator in each string. What is the operating voltage of the transmission line?
a) 11 KV
b) 33 KV
c) 66 KV
d) 132 KV
Answer
Answer: d [Reason:] For different voltage it does not need to use different suspension insulator. Srength of insulator can easily be increased just by adding extra disc of suspension insulators. For 130 KV transmission lines 9 or 10 disks are used.
6. Suspension insulator are made up of _______
a) glass
b) porcelain
c) steatite
d) epoxy resin
Answer
Answer: b [Reason:] Suspension insulators consist of a number of porcelain disks flexibly connected in series by metal links in the form of Strings. Glass is used for making pin type insulators.
7. Which of the following insulator is similar to pin type insulator?
a) Suspension insulator
b) Post insulator
c) Strain insulator
d) Shackle insulator
Answer
Answer: b [Reason:] Post insulators are very similar to pin type insulator, but has a metal base with a metal cap so that more than one unit can be mounted in series. Suspensions train and shackle insulators are completely different from pin type insulator on the basis of construction.
8. Which type of insulator is used where there is dead end of the line or there is a corner or a sharp curve, for high voltage line?
a) Pin type insulator
b) Shackle insulator
c) Strain insulator
d) Stay insulator
Answer
Answer: c [Reason:] Pin type insulators cannot be used in such situations because they cannot take conductor mechanical load intention which often occurs in such situations for low voltage line. Shackle insulator can be used but for higher voltages transmission lines strain insulator consisting of assembly of suspension type insulator are used.
9. What is the most common cause of failure of overhead line insulators?
a) Flashover
b) Mechanical stress
c) Porosity of materials
d) Improper vitrification
Answer
Answer: a [Reason:] Failure of overhead line insulators due to mechanical stress is rare because defective pieces are separated during routine factory test. Failure due to porosity and improper vitrification is also very low. The most common cause of failure of overhead line insulator is flashover.
10. If a string of suspension insulator has three units, each can withstand a maximum 11 KV and total string can withstand 25.76 KV. What is the string efficiency?
a) 234.1%
b) 46.3%
c) 68.75%
d) 78%
Answer
Answer: d [Reason:] String Efficiency = [( flashover voltage of the string) /(n × flashover voltage of 1 unit)] × 100
Where ‘n’ is number of units in one string
Hence, String Efficiency = [25.76/(3×11)] × 100
= 78%.
11. Voltage distribution across disc of strings of suspension insulator assembly is ______
a) same for all disks
b) maximum for unit nearest to the line
c) maximum for unit nearest to the tower
d) equal to transmission line voltage rating
Answer
Answer: b [Reason:] Thee voltage between line conductor and Earth is not distributed uniformly across individual disks. The unit nearest the conductor has the maximum value across it. The figure progressively decreases as the unit nearest the cross on is approach.
Power Systems MCQ Set 4
1. Which of the following is the correct equation for the electrical power generated by the hydroelectric power plant?
a) 75×0.736 wQHη Watt
b) (7.5/0.736) × wQHη Watt
c) 0.845 ×wQHη Watt
d) 9.81 ×wQHη
Answer
Answer: c [Reason:] Rating of any power plant is expressed by its maximum output power. These are large quantities so rating is given in mega watts.The electrical power generated by this plant is proportional to specific weight of water(w), water head(H), generation efficiency(η), flow rate of water(Q) and acceleration due to gravity.
2. Which of the following is not a requirement for site selection of hydroelectric power plant?
a) Availability of water
b) Large catchment area
c) Rocky land
d) Sedimentation
Answer
Answer: d [Reason:] Sedimentation may reduce the water storage capacity of reservoir and may also cause damage to the turbine blades. Availability of water, large catchment area and rocky land are primary requirements for site selection of hydroelectric power plant.
3. The amount of electrical energy that can be generated by a hydroelectric power plant depends upon _____
a) Head of water
b) Quantity of water
c) Specific weight of water
d) Efficiency of Alternator
Answer
Answer: b [Reason:] Potential energy of large quantity of stored water is used by hydroelectric power plant to generate electrical energy. Head of water is important to get kinetic energy from that potential energy. Efficiency of alternator represents that what percentage of input mechanical power it can convert into electrical power.
4. Potential energy of water is used to drive the turbine.
a) True
b) False
Answer
Answer: b [Reason:] When water falls, potential energy of water is converted into kinetic energy. This kinetic energy is used to drive the turbine.
5. Hydroelectric power plant is ____
a) Non-renewable source of energy
b) Conventional source of energy
c) Non-conventional source of energy
d) Continuous source of energy
Answer
Answer: b [Reason:] Hydroelectric power plants are conventional source of energy. About 16.6% of total electricity and about 70% of total renewable energy of world is provided by hydroelectric power plants. They are not Non-renewable because water is inexhaustible. It is not continuous source of energy because its output fluctuates with change in flow rate of water with season.
6. Hydroelectric power plant is generally located near load centre.
a) True
b) False
Answer
Answer: b [Reason:] Hydroelectric power plants are generally constructed in hilly areas. These power plants are quite away from the load centre.
7. Hydroelectric power plant is mainly located in ______
a) Flat areas
b) Deserts
c) Hilly areas
d) Deltas
Answer
Answer: c [Reason:] In order to get sufficient head, hydroelectric power plants are constructed in hilly areas. In desert and flat areas sufficient water head cannot be obtained. Deltas are not suitable for this because of high sedimentation.
8. Which statement about hydroelectric power plant is wrong?
a) Efficiency of hydroelectric power plant does not reduce with age
b) Its construction coast is very high and takes a long time for erection.
c) It is very neat and clean plant because no smoke or ash is produced.
d) Meeting rapidly changing load demands is not possible in hydroelectric power plant.
Answer
Answer: d [Reason:] Fluctuating load demands can be met just by controlling the flow of water using valves and gates. Due to its robust construction, its efficiency does not fall with time. Statement ‘b’ is correct because construction of dam, installation of alternator and turbines are very costly.
9. Which of the following is not an advantage of hydroelectric power plant?
a) no fuel requirement
b) low running cost
c) continuous power source
d) no standby losses
Answer
Answer: c [Reason:] Output of such plants is never constant. This is because of their dependency over flow rate of water in river which is seasonal. No fuel requirement low running cost and no standby losses are advantages of hydroelectric power plants.
10. Which of the following statement is true about hydroelectric power plant?
a) Hydroelectric power plants are multipurpose.
b) Due to non-uniform flow of water frequency control in such plants is very difficult.
c) Hydroelectric power plant has high running cost
d) Water is used as fuel in hydroelectric power plant
Answer
Answer: a [Reason:] It is because in addition to generation of electricity they are also used for irrigation, flood control etc. Frequency control in such plants is done easily just by controlling flow of water to the turbine through valves and gates. Due to low maintenance cost and no fuel requirement running cost of a plant is very low. Water is not fuel.
Power Systems MCQ Set 5
1. The best capable alternative source which can meet the future energy demand is _______
a) thermal power plant
b) nuclear power plant
c) hydroelectric power plant
d) geothermal power plant
Answer
Answer: b [Reason:] Demand of electrical energy is increasing at fast rate owing to booming increase in the population and industrial growth. The reserves of fossil fuel i.e., coal, oil and gas are fast depleting. There are many alternative sources of energy but they are not enough to supply such huge demand, only nuclear power plants are capable of doing that.
2. How much coal is required to generate energy equivalent to the energy generated by 1 kg of uranium?
a) 30000 tonnes of high grade coal
b) 300 tonnes of high grade coal
c) 10000 tonnes of high grade coal
d) 3000 tonnes of high grade coal
Answer
Answer: d [Reason:] One of the main attention for nuclear fuel is the huge amount of energy that can be released from a small quantity of active nuclear fuel. The energy obtainable by completely using 1 kg of Uranium would give energy equivalent 3000 tons of high grade coal i.e. Uranium has three millions times the energy of coal.
3. Nuclear fuel in reactor lasts for ____
a) more than 5 months
b) few weeks
c) few days
d) more than 5 years
Answer
Answer: d [Reason:] Very small amount of nuclear fuel can produce very high amount of energy. Nuclear fuel may remain in a reactor for more than 5 years.
4. Cost of nuclear fuel in nuclear power plant economics is considered as ____
a) running cost
b) maintenance cost
c) capital cost
d) development cost
Answer
Answer: c [Reason:] Nuclear fuel in a nuclear reactor may remain for more than 5 years. So the cost of fuel injected initially is taken as capital cost and may be a few crore rupees.
5. In economics of nuclear power plant taxes and insurance charges are taken as _______
a) operating cost
b) maintenance cost
c) capital cost
d) fixed cost
Answer
Answer: d [Reason:] The life of reactor plant may be taken as between 15 to 20 years. For the other parts of the plant equipment the life may be taken as 30 years. The fixed cost would be interest, depreciation, taxes and insurance charges.
6. Which of the following are not taken as operation and maintenance cost in economics of nuclear power plant?
a) Taxes and insurance
b) Salaries and wages of staff
c) Cost of waste disposal
d) Cost of processing materials
Answer
Answer: a [Reason:] Taxes and insurance are taken as fixed costs. Salaries and wages of operation and maintenance staff, cost of waste disposal and cost of processing materials are the operation and maintenance cost.
7. What is the overall efficiency of nuclear power plant?
a) 20 to 25%
b) 25 to 30%
c) 30 to 40 %
d) 50 to 70 %
Answer
Answer: c [Reason:] The overall efficiency of a nuclear power plant is around 30 to 40%. Efficiency is higher at high road factors. Therefore, a nuclear power plant is always operated as a base load plant.
8. The land area required for installation of nuclear power plant is ________
a) more than thermal power plant
b) less than thermal power plant
c) equel to thermal power plant
d) depends on type of construction
Answer
Answer: c [Reason:] Nuclear power plants need less area as compared to any other plant of same generation capacity. A 2000MW nuclear power plant needs about 80 acres whereas the coal fired steam power plant of same generation capacity needs 250 acres of land.
9. All of the nuclear fuel reserve will be ended in about 400 years.
a) True
b) False
Answer
Answer: b [Reason:] There are larger deposits of nuclear fuel available all over the world. Therefore, such plants can ensure continued supply of electrical energy for thousands of years.
10. With respect to the load centre which location is suitable for stablishment of nuclear power plant?
a) Load centre
b) Near load centre but at reasonable distance
c) Far away from load centre
d) Near chemical industries
Answer
Answer: b [Reason:] These plants can be located near the load centre because of the negligible cost of transportation of fuel. But there should be a reasonable distance between the nuclear power plant and the nearest populated areas from point of view of safety against danger of radioactivity. It is highly undesirable to choose a site adjacent to chemical industries oil refineries PWD works hospitals and schools.
11. Operating cost of nuclear power plant is less than thermal power plant.
a) True
b) False
Answer
Answer: a [Reason:] Cost of fuel in nuclear power plant is taken as the capital cost. The the total operating cost involves wages and the salaries of operating and maintenance staff only, cost of disposal of waste etc.. The cost of transport and handling of coal for conventional thermal power plant is much higher than the cost of nuclear fuel.
