Power Systems MCQ Set 1
1. For a transmission line of length not more than 80 km, then it is convenient to lump the capacitance at ________
a) receiving end
b) sending end
c) midpoint
d) anywhere long the line
Answer
Answer: a [Reason:] The capacitance should be best lumped at the receiving end for the simpler calculations.
2. At the no load conditions, the current is detected in the transmission line. This can be attributed due to ____
a) capacitance effect
b) proximity effect
c) corona effect
d) back flow through earth
Answer
Answer: a [Reason:] At the no load current the shunt connected capacitance allows the flow of the current through the circuit.
3. Identify the characteristics of the Ferranti effect.
(i) Flow of unduly heavy current
(ii) It occurs at unloaded condition
(iii) Rise in the receiving end voltage
a) (i) ad (ii)
b) (ii) ad (iii)
c) (i) ad (iii)
d) (ii) ad (iii)
Answer
Answer: d [Reason:] Ferranti effect occurs at no load condition and it causes rise in voltage.
4. Ferranti effect is very prominent in occurrence in what type of transmission line?
a) Long and unloaded
b) Short and loaded
c) Long and unloaded
d) Short and unloaded
Answer
Answer: a [Reason:] Ferranti effect occurs more in long TL and especially when they are not loaded.
5. The transmission line parameters ABCD for a three phase transposed line with passive and linear elements are ______
a) always equal
b) never same
c) A and D are same
d) B and C are same
Answer
Answer: a [Reason:] The A and D parameter will only be constant.
6. For a general transmission system, the calculated parameter A for a medium transmission line has magnitude _______
a) close to but less than 1
b) close to but more than 1
c) average of B and C parameter
d) none of the mentioned
Answer
Answer: a [Reason:] |A| < 1 but less than 1.
7. The impedance known as surge impedance and characteristic impedance are same.
a) True
b) False
Answer
Answer: a [Reason:] Both the impedances are same.
8. Characteristic impedance of a transmission line depends upon ______
a) geometrical configurations of conductor
b) shape of conductor
c) conductivity
d) surrounding of the conductor.
Answer
Answer: a [Reason:] Characteristic impedance of a transmission line will depend on conductor configuration.
9. What will happen when the characteristic impedance of a transmission line is equal t the load impedance ________
a) all the given energy will be absorbed by the load
b) all the given energy will be transferred to load
c) system will undergo resonance
d) all the given energy will be lost in transmission losses.
Answer
Answer: a [Reason:] When the characteristic impedance will be same as load then the load will absorb all the energy.
10. The transmission capacity of a line at 50 Hz frequency as compared to that at 60 Hz is ______
a) higher
b) lower
c) same
d) can’t be decided
Answer
Answer: a [Reason:] Due to drop in frequency the losses will reduce.
11. Use of additional shunt capacitor can be made for increasing the capability of the line as it will ______
a) reduce surge impedance
b) increase phase shift
c) increase the angle α
d) all of the mentioned
Answer
Answer: a [Reason:] Due to addition of capacitance, the impedance will reduce and power capability will increase.
12. To increase the transmission capability of a high voltage long line ______
a) series reactance can be reduced
b) resistance can be increased
c) resistance can be decreased
d) shunt admittance can be reduced
Answer
Answer: a [Reason:] Transmission capability is inversely proportional to the reactance.
Power Systems MCQ Set 2
1. The presence of ozone while the corona has occurred, can be found using ________
a) pressure
b) hissing noises
c) faint luminous glow of bluish colour
d) all of the mentioned
Answer
Answer: d [Reason:] The ozone can be easily detected by all the mentioned effects occurring in the system.
2. The corona has only disadvantages to the transmission system.
a) True
b) False
Answer
Answer: b [Reason:] Corona is helpful while the surges are there.
3. The very peculiar advantage of corona in the circuit can be _____
a) reduction in steepness of surge fronts
b) improvement of power factor
c) reduction in radio interference
d) reduction in steepness, radio interference and improvement of PF
Answer
Answer: a [Reason:] Corona reduces the surge occurring in the system.
4. When the ozone gas is produced as a by product of corona, that causes _______
a) corrosion of wires
b) reduction of power factor
c) increase of power factor
d) improvement of regulation
Answer
Answer: a [Reason:] Ozone gas corrodes the metals.
5. Critical voltage limit of the transmission line can be increased by ______
a) increasing conductor’s radius
b) increasing conductor spacing
c) reducing conductor spacing
d) reducing radius of conductor
Answer
Answer: a [Reason:] Vα 1/r.
6. In a transmission system, the transmission parameters of distribution is/are _____
a) resistance
b) inductance
c) capacitance and shunt conductance
d) resistance, inductance, capacitance and shunt conductance
Answer
Answer: d [Reason:] R, L, C, G are the distribution constants.
7. Following effects of the transmission lines
(i) Skin effect
(ii) Corona
(iii) Proximity
The effective resistance of the conductor is increased by ____
a) (i), (ii)
b) (i), (iii)
c) (ii), (iii)
d) (i), (ii), (iii)
Answer
Answer: d [Reason:] Effective resistance increases by skin effect, corona as well as proximity effect.
8. _______ is neglected while carrying out short transmission line analysis.
a) Shunt admittance
b) Power losses
c) Series impedance
d) None of the mentioned
Answer
Answer: a [Reason:] Shunt admittance is neglected.
9. We transpose high voltages especially while transmitting so that the ____
a) phase voltage imbalances can be minimised
b) corona losses are reduced
c) voltage drop is minimised
d) all of the mentioned
Answer
Answer: a [Reason:] Transposition reduces the phase voltage imbalances by cancelling their effects.
10. While modelling a short transmission line of the overhead lines, line resistance and inductances are only considered because the line capacitance is _____
a) zero
b) finite but small
c) finite but large
d) infinite
Answer
Answer: b [Reason:] Capacitance for such a distance is small and negligible.
Power Systems MCQ Set 3
1. Reactors used for electricity generation are called ________
a) Research and development reactors
b) Production reactors
c) Power reactors
d) Electron reactors
Answer
Answer: c [Reason:] Power reactors are used for electrical power generation purpose. Research and development reactors are used for testing new reactor design ans research. Production reactors are used for converting fertile material into fissile materials.
2. What is the difference in size of thermal reactor and fast reactor?
a) Size of thermal reactor is slightly more than size of fast reactor
b) Size of thermal reactor is slightly less than size of fast reactor
c) Size of thermal reactor is very much larger than size of fast reactor
d) Both are of same size
Answer
Answer: c [Reason:] The moderator to fuel volume ratio for thermal reactor lies between 20 to 80. Same ratio for fast reactor is very less that’s why the size of thermal reactor is very much greater than size of fast reactors.
3. Which of the following reactors does not need moderator?
a) Thermal reactor
b) Fast reactor
c) Intermediate reactor
d) Power reactor
Answer
Answer: b [Reason:] In fast reactors fission is caused by fast neutrons, so there is no need of moderator to slow down the neutrons. While in other reactors fission is needed to be from slow or intermediate speed neutrons, so moderator is required to slow down the fast neutrons.
4. Heat energy generated in per unit volume of reactor core in thermal reactor is _____
a) less than that in fast reactors
b) more than that in fast reactors
c) equal to that and fast reactors
d) unpredictable
Answer
Answer: a [Reason:] In fast reactors fission occurs due to fast moving neutrons. Hence, the rate of fission reaction is high and the heat energy generated is also very high. In thermal reactor moderator is used to slow down the neutrons and to make the fission in much more controlled way. So, heat generated in thermal reactor is cocomparatively less.
5. In which of the following reactors material converted into fissile materials is more than fissile material consumed?
a) Burner reactor
b) Slow reactors
c) Converter reactor
d) Breeder reactor
Answer
Answer: d [Reason:] Burner reactor or thermal reactor is designed only to consume fissile materials and to give heat energy. Converter reactor converts fertile material into fissile material but the rate of conversion is slower than rate of conception. Only breeder reactor from above options is such a reactor which converts fertile materials into fissile materials faster than consumption of fissile materials.
6. Which of the following reactors uses its fuel as coolant?
a) Direct reactor
b) Indirect reactor
c) Both direct and indirect reactor
d) Solid fuel reactor
Answer
Answer: a [Reason:] On the basis of cooling system employed reactors are of two types. One is Direct and another is indirect reactor. Direct reactor used as fuel in liquid form and it acts as coolant. It is circulated through the heat exchanger in which heat is transferred to water to produce steam.
7. Which of the following statement is true?
I. In homogeneous reactors the nuclear fuel and the moderator represents a uniform mixture in the fluid form.
II. In heterogeneous reactors separate fuel sludge or roads are inserted in the moderator
III. Most of the nuclear reactors used these days are of homogeneous type
a) Only statement I and II are true
b) Only statement I and III are true
c) Only statement II and III are true
d) Only statement III is true
Answer
Answer: a [Reason:] The statement I and II are true but statement III is wrong, because most of the reactors are of heterogeneous type. i.e.fuel is used in them are separate mostly in form of road fuel rod.
8. In which of the following reactor it is possible to add remove and process the reactor fuel during reactor operation?
a) Homogeneous reactor
b) Heterogeneous reactor
c) Solid fuel reactor
d) Both homogeneous and heterogeneous reactors
Answer
Answer: a [Reason:] In homogeneous reactor nuclear fuel and the moderator represent a uniform mixture, in the fluid form including gases liquids and slurries. Due to fluid form of fuel it is possible in homogeneous reactor that reactor fuel can be added removed and reprocessed during reactor operation without shutting in town.
9. In which of the following reactors fissile and fertile materials are kept separate?
a) In one region reactor
b) In two region reactor
c) In one and two region reactor
d) It is impossible to separate them
Answer
Answer: b [Reason:] As per arrangement of fertile and fissile materials the reactors are classified into categories. In first category of reactors fertile and fissile fuels are mixed and are called One Region Reactor. In second category of reactors a fertile and fissile material are separate and is called to Region Reactor.
10. Any leakage or component failure in primary nuclear fission reactor coolant system is dangerous.
a) True
b) False
Answer
Answer: a [Reason:] Above statement is true because these failures are very much difficult to repair. It is because of the presence of fission products in the coolant which can cause contamination.
Power Systems MCQ Set 4
1. A three phase transformer has a name plate details of 30 MVA and voltage rating of 230Y kV/69∆ kV with a leakage reactance of 10% and the transformer connection via wye-delta. Taking a base of 230 kV on the high voltage side, turns ratio of the windings is ______
a) 2
b) 1.5
c) 6
d) 4
Answer
Answer: a [Reason:] n= VHV/VLV = (230/√3)/69=1.9245.
2. A three phase transformer has a name plate details of 30 MVA and voltage rating of 230Y kV/69∆ kV with a leakage reactance of 10% and the transformer connection via wye-delta. Taking a base of 230 kV on the high voltage side, the transformer reactance on the LV side is
_____
a) 176.33 Ω
b) 1763.3 Ω
c) 47.6 Ω
d) 15.87 Ω
Answer
Answer: a [Reason:] Zb(HV) = kVb(HV))2/MVAb
Zb(HV) = 2302/30=1763.33 Ω
XΩ =0.1*1763.33 = 176.33 Ω.
3. A three phase transformer has a name plate details of 30 MVA and voltage rating of 230Y kV/69∆ kV with a leakage reactance of 10% and the transformer connection via wye-delta. Taking a base of 230 kV on the high voltage side, the transformer reactance referred to the low voltage side in ohms is ____
a) 47.61 Ω
b) 15.87 Ω
c) 176.33 Ω
d) 157.8 Ω
Answer
Answer: a [Reason:] Zb(HV) = (kVb(HV)2/MVAb = 2302/30=1763.33 Ω
XΩ(HV) =0.1*1763.33 = 176.33 Ω
XΩ(LV) =176.33/(1.92452) = 47.61 Ω.
4. A three phase transformer has a name plate details of 30 MVA and voltage rating of 230Y kV/69∆ kV with a leakage reactance of 10% and the transformer connection via wye-delta. Taking a base of 230 kV on the high voltage side, the transformer reactance referred to the low voltage side in ohms is
a) 0.1
b) 0.2
c) 0.198
d) 0.4
Answer
Answer: a [Reason:] XΩ(LV) = XΩ(HV) /n2
= 176.33/(230/69)2 =15.87 Ω
Xpu= 15.87/158.7 = 0.1.
5. A 200 bus power system has 160 PQ bus. For achieving a load flow solution by N-R in polar coordinates, the minimum number of simultaneous equation to be solved is _____
a) 359
b) 329
c) 360
d) 320
Answer
Answer: a [Reason:] Total buses = 200
PQ buses = 160
PV buses = 200-160 = 40
Slack bus = 1
Total number of equation = (40-1)*1 + (160*2) = 359.
6. Two alternators A and B having 5% speed regulation are working in parallel at a station. Alternator A is rated at 15 MW while B is at 20 MW. When the total load to be shared is 12 MW, then how much of the load will be shared by the alternator B?
a) 6.85 MW
b) 5.14 MW
c) 6 MW
d) 7 MW
Answer
Answer: a [Reason:] 1 α15 ;
P2 α 20;
P1 = 0.75 P2 …(1)
P1 +P2 = 12 …(2)
Solving above, P2 = 6.85 MW.
7. Two alternators A and B having 5% speed regulation are working in parallel at a station. Alternator A is rated at 15 MW while B is at 20 MW. When the total load to be shared is 12 MW, then how much of the load will be shared by the alternator B?
a) 6.85 MW
b) 5.14 MW
c) 6 MW
d) 7 MW
Answer
Answer: a [Reason:] 1 α15 ;
P2 α 20;
P1 = 0.75 P2 …(1)
P1 +P2 = 12 …(2)
Solving above equations, P1 = 5.14 MW.
8. A 400 V, 50 Hz three phase balanced source ripples to a star connected load whose rating is S(=300+j400) kVA. The rating of the delta connected capacitor bank needed to bring p.f. to 0.9 lagging is _______ KVAR.
a) 254.7
b) 25.4
c) 84.9
d) 284.5
Answer
Answer: a [Reason:] Qc = P[tanθ1 – tanθ2]
=300[(4/3) – cos-10.9] = 254.72 kVAR.
9. A 400 V, 50 Hz three phase balanced source ripples to a star connected load whose rating is S(=300+j400) kVA. A delta connected capacitor bank needed to bring p.f. to 0.9 lagging. The operating power factor of the system is
a) 0.8
b) 4/3
c) 3/4
d) 0.6
Answer
Answer: a [Reason:] cosФ = 3/5 = 0.6.
10. A given system to be analysed was found with the below phasor representation of the system voltages. Which of the symmetrical components will be present in the mentioned system?
a) Positive sequence components
b) Negative sequence components
c) Zero sequence components
d) All of the mentioned
Answer
Answer: a [Reason:] In an unbalanced system, all the symmetrical components will be present.
11. The phasor operator which is used to depict the unbalanced phase voltages into three phase quantities, provides a rotation of
a) 120o counter clockwise
b) 120o clockwise
c) 90o counter clockwise
d) 90o clockwise
Answer
Answer: a [Reason:] ‘α’ operator used for the conversion has the counter clockwise rotation of the quantity and it has unity magnititude.
Power Systems MCQ Set 5
1. For the figure depicting the two generators connected via the transmission line having and impedance ‘jX’ ohms. Machine A at voltage Va at angle δ will supply active power to machine B at voltage Vb and angle zero, when δ is _______
a) positive
b) negative
c) zero
d) any of the mentioned
Answer
Answer: a [Reason:] The real power transfer takes place when the power angle is greater than the other station.
2.For the figure depicting the two generators connected via the transmission line having and impedance ‘jX’ ohms. Machine A at voltage Va at angle δ will supply active power to machine B at voltage Vb and angle zero, when δ is _______
a) Va>Vb
b) Va<Vb
c) Va = Vb
d) Any of the mentioned.
Answer
Answer: a [Reason:] The reactive power that will flow through the system when the voltage of the bus is more than the other one.
3. A three phase alternator can supply a maximum of 5000 KVA at 66 kV. The machine has internal resistance of 6%. The reactance per phase of the limiting reactor if the steady apparent power on the short circuit do not exceed 5 times full load is ______
a) 1.22 Ω
b) 2.44 Ω
c) 5 Ω
d) 1.84 Ω
Answer
Answer: a
4. A transmission line has Z= (2+j8)Ω has 10% of the voltage regulation with the lagging load of 0.8. If the load is 0.707 leading, the V.R. is ________(Assume the current is same in both cases)
a) -6.63%
b) -5.77%
c) -10%
d) -8.63%
Answer
Answer: a
5. A generating station has a connected load of 43 MW. The unit generated having 61.5*106 per year. The load factor will be _______
a) 0.35
b) 0.33
c) 0.5
d) 0.45
Answer
Answer: a
6. The symmetrical components are used in fault analysis because of ___
a) sequence of network do not have mutual coupling
b) number of equations is smaller
c) results are required in symmetrical components
d) none of the mentioned
Answer
Answer: a [Reason:] Due the non-coupling of the transmission system sequence network it is easy to implement symmetrical fault analysis.
7. Two conductors of a single phase line, having the 1cm diameter and arranged in a vertical plane with one conductor mounted 1m above other. A second identical line is mounted at same height as first and spaced horizontally 0.25m apart. The two upper and lower conductors are connected in parallel. The loop inductance of the line is ______(mH/km)
a) 0.84
b) 0.42
c) 0.32
d) 0.64
Answer
Answer: a
8. Two conductors of a single phase line, having the 1cm diameter and arranged in a vertical plane with one conductor mounted 1m above other. A second identical line is mounted at same height as first and spaced horizontally 0.25m apart. The two upper and lower conductors are connected in parallel. The inductance of the line is ____(mH/km)
a) 0.42
b) 0.84
c) 0.55
d) 0.80
Answer
Answer: a
9. A transmission line has line parameters A =0.8, B= 200ʟ90o, C = 0.5*10-6 operating at 400kV at no load. The sending current in line will be _____
a) 0.1443
b) 1.443
c) 0.324
d) 3.245
Answer
Answer: a
10. A 2-wire ring distributor is 300m long and fed at 240V at ‘A’. At ‘B’, 150m away from A, a load of 120A is taken and at ‘C’, 100m away in opposite direction a load of 80A is taken. If the resistance per 100m of single conductor is 0.03Ω, then current in section AB feeder is _____
a) 86.67 A
b) 48.76 A
c) 88 A
d) 98.4 A
Answer
Answer: a [Reason:] Resistance per 100m of distributor = 2*0.03 = 0.06Ω
