53 + Mcqs in Power System - Transmission and Distribution Page 1 McqOptions

1.	The cost of material used in a distribution circuit per kVA of the distributed power varies as
A.	Square of linear dimensions of supply area.
B.	Directly according to (supply area)
C.	Cube of linear dimensions of supply area
D.	None of these
Answer» C. Cube of linear dimensions of supply area

Discussion

2.	What will be the pd at point B if a pd of 300 V is maintained at a point A, for a 2 wire dc distributor cable AB if 2 km long and supplies loads of 100A, 150A, 200A, and 50A suited at 500m, 1000m, 1600m, and 2000m from the feeding point A. Each conductor has a resistance of 0.01 per 1000 m.
A.	288 V
B.	287.6 V
C.	295.36 V
D.	291.2 V
Answer» C. 295.36 V

Discussion

3.	What is the loss factor in a distribution system?
A.	0.3 * load factor + 0.7 (load factor)
B.	0.5 * (load factor)
C.	Load factor
D.	0.7 * load factor + 0.3 (load factor)
Answer» B. 0.5 * (load factor)

Discussion

4.	A 2 wire dc street mains AB, 600 m long is fed from both ends at 220 V. Loads of 20 A, 40 A, 50 A and 30 A are tapped at distances 100m, 250m, 400m and 500m from the end A. If the area of cross section of distributor is 1 cm, what will be the minimum consumer voltage? If ? = 1.7 * 10 cm.
A.	220 V
B.	215.69 V
C.	218.36 V
D.	222.58 V
Answer» C. 218.36 V

Discussion

5.	Installation of capacitors at suitable locations and of optimum size in a distribution system results ini. Improved voltage regulation.ii. Reduction in distribution power losses.iii. Reduction of kVA rating of distribution transformers.Which among the above statements are correct?
A.	i only
B.	i and ii only
C.	iii only
D.	All of these
Answer» E.

Discussion

6.	A 300m ring distributor has loads as shown in the fig. The distances are in metres. The resistance of each conductor is 0.2 W per 1000 metres and loads are tapped off at B, C, D. If the distributor is fed at A at 240 V, what will be the voltage at B?
A.	220.6 V
B.	236.9 V
C.	240.6 V
D.	235.97 V
Answer» C. 240.6 V

Discussion

7.	In a balanced 3 phase, 4 wire ac system the phase sequence is RYB. If the voltage of R phase = 230 0 volts, then what will be the B phase?
A.	230 - 120
B.	230 - 90
C.	230 - 90
D.	230 - 120
Answer» B. 230 - 90

Discussion

8.	A single phase AC distributor supplies two single phase loads as shown. What is the voltage drop from A to C?
A.	4.5 V
B.	30 V
C.	31.5 V
D.	20 V
Answer» D. 20 V

Discussion

9.	Strain and Shackle type insulators are provided on which type of plane?
A.	Vertical plane
B.	Horizontal plane
C.	On the surface
D.	All of these
Answer» B. Horizontal plane

Discussion

10.	Assertion (A): Glazing on ceramic insulators is done to make it smooth and non absorbent.Reason (R): Moisture from atmosphere collects on the surface causing electrical breakdown.
A.	Both A and R are true and R is the correct explanation of A
B.	Both A and R are true and R is not the explanation of A
C.	A is true but R is false
D.	A is false but R is true
Answer» B. Both A and R are true and R is not the explanation of A

Discussion

11.	In a test by Murray loop for ground fault on 500 m of cable having a resistance of 1.6 / km, the faulty cable is looped with the sound cable of some length and area of cross section. If the ratio of the other two arms of the testing network at balance is 3:1, what is the distance of fault from the testing end of cables?
A.	100 m
B.	200 m
C.	250 m
D.	300 m
Answer» D. 300 m

Discussion

12.	Assertion (A): The string efficiency can be improved by using long cross arms.Reason (R): Use of long cross arms reduces the ratio of capacity to earth to capacity per insulator thereby increasing the string efficiency.
A.	Both A and R are true and R is the correct explanation of A
B.	Both A and R are true and R is not the explanation of A
C.	A is true but R is false
D.	A is false but R is true
Answer» B. Both A and R are true and R is not the explanation of A

Discussion

13.	Assertion (A): Capacitance grading improves the string efficiency not more than 220 kV.Reason (R): In capacitance grading the units used are of different capacitance and so are not interchangeable.
A.	Both A and R are true and R is the correct explanation of A
B.	Both A and R are true and R is not the explanation of A
C.	A is true but R is false
D.	A is false but R is true
Answer» E.

Discussion

14.	Which of the following statements are true related to corona?
A.	1,2,4
B.	1,4
C.	1,2,3
D.	2,3
Answer» D. 2,3

Discussion

15.	Corona loss can be reduced by using
A.	1 only
B.	1 and 2 only
C.	1, 2 and 3 only
D.	2 and 3 only
Answer» E.

Discussion

16.	By what factor does the critical disruptive voltage (V) get reduced?
A.	0.6
B.	0.7
C.	0.8
D.	0.9
Answer» D. 0.9

Discussion

17.	Skin effect is negligible for what supply frequency and for what diameter?
A.	< 50 Hz and < 1 cm
B.	< 50 Hz and > 1 cm
C.	> 50 Hz and < 1 cm
D.	> 50 Hz and > 1 cm
Answer» B. < 50 Hz and > 1 cm

Discussion

18.	Find the spacing between the conductors a 132 kV 3 phase line with 1.956 cm diameter conductors is built so that corona takes place, if the line voltage exceeds 210 kV (rms). With g = 30 kV/cm.
A.	1.213 m.
B.	2.315 m.
C.	3.451 m.
D.	4.256 m.
Answer» D. 4.256 m.

Discussion

19.	Skin effect in a conductor is proportional to
A.	(Diameter of conductor)
B.	Diameter of conductor
C.	(Diameter of conductor)
D.	(Diameter of conductor)
Answer» B. Diameter of conductor

Discussion

20.	Assertion (A): Transposition of conductors in a transmission line is necessary.Reason (R): Corona losses are reduced by transposition of conductors.
A.	Both A and R are true and R is the correct explanation of A
B.	Both A and R are true and R is not the explanation of A
C.	A is true but R is false
D.	A is false but R is true
Answer» D. A is false but R is true

Discussion

21.	What is the charging current per km for the transmission line shown in the figure. Operating at 132 kV, the conductor diameter is 0.8 cm.
A.	0.314 A/km
B.	0.21 A/km
C.	0.45 A/km
D.	0.11 A/km
Answer» C. 0.45 A/km

Discussion

22.	A three phase, 50Hz transmission line consists of three equal conductors of radii r placed in a horizontal plane with a spacing of 6m between middle and outer conductor. If the radius of each conductor is 12.5 mm, then inductance per phase per km of the transposed line will be
A.	1.33 mH/km
B.	1.65 mH/km
C.	0.38 mH/km
D.	2.145 mH/km
Answer» B. 1.65 mH/km

Discussion

23.	What is the inductance per phase per km of a double circuit 3 phase line as shown in the fig. The conductors are transposed and are of radius 0.75 cm each.
A.	0.725 mH
B.	0.835 mH
C.	0.623 mH
D.	0.231 mH
Answer» D. 0.231 mH

Discussion

24.	Assertion (A): the concept of GMD is applicable for the calculation of inductance of transmission lines.Reason (R): The radius of the conductor of transmission lines, in the expression for inductance is not the self GMD of the conductor.
A.	Both A and R are true and R is the correct explanation of A
B.	Both A and R are true and R is not the explanation of A
C.	A is true but R is false
D.	A is false but R is true
Answer» C. A is true but R is false

Discussion

25.	Capacitance between the two conductors of a single phase two wire line is 0.5 F/km. What is the value of capacitance of each conductor to neutral?
A.	0.5 F / km
B.	1 F / km
C.	0.25 F / km
D.	2.0 F / km
Answer» C. 0.25 F / km

Discussion

26.	The ABCD parameter of a 3 phase transmission line is given as followsA = D = 0.9 0 , B = 200 90 , and C = 0.95 *10 90 . At no load condition a shunt inductive reactor is connected at the receiving end of the line to limit the receiving end voltage to be equal to the sending end voltage. What is the ohmic value of the reactor?
A.	Infinity
B.	2000
C.	105.26
D.	1052.6
Answer» C. 105.26

Discussion

27.	What is the line length if a load of 15000 kW at a power factor 0.8 lagging can be delivered by a 3 phase transmission line having conductors each of resistance 1 per kilometre? The voltage at the receiving end is to be 132kV and the loss is about 5%.
A.	40.13km
B.	37.18km
C.	42.38km
D.	35.87km
Answer» C. 42.38km

Discussion

28.	The ABCD constants of a 3 phase transposed transmission line with linear and passive elements ________________.
A.	are always equal
B.	never equal
C.	only A and D are equal
D.	only B and C are equal
Answer» D. only B and C are equal

Discussion

29.	What are the A and D parameters in case of medium transmission line (nominal T method)?
A.	A = D = 1 + (YZ / 2)
B.	A = D = 1 + (YZ / 2) * Z
C.	A = D = (YZ / 2)
D.	A = D = (YZ / 2) * Y
Answer» B. A = D = 1 + (YZ / 2) * Z

Discussion

30.	What is the value of the C parameter by using a nominal T method for a 3 phase balanced load of 30 MW which is supplied by a 132 kV, 50 Hz and 0.85 pf lagging? The series impedance of a single conductor is (20 + j52) and the total phase to neutral admittance is 315 * 10 siemen.
A.	0.000315 90
B.	0.000251 90
C.	0.004125 90
D.	0.000289 90
Answer» B. 0.000251 90

Discussion

31.	What is the limit of the conductor cross section when paper insulation is used?
A.	50 mm
B.	250 mm
C.	600 mm
D.	1200 mm
Answer» D. 1200 mm

Discussion

32.	The ABCD parameter of a 3 phase transmission line is given as followsA = D = 0.8 1 , B = 170 85 , and C = 0.002 90.4 the sending end voltage is 400 kV. What is the receiving end voltage under no load condition?
A.	400 kV
B.	500 kV
C.	320 kV
D.	417 kV
Answer» C. 320 kV

Discussion

33.	Correctly match the items in List 1 to the items in List 2: List 1List 2Codes:
A.	2 1 3 4
B.	1 2 4 3
C.	3 4 2 1
D.	4 3 1 2
Answer» B. 1 2 4 3

Discussion

34.	The insulation resistance of a cable of length 10 km is 1M . For a length of 100 km of the same cable, what will be the insulation resistance?
A.	1 M
B.	10 M
C.	0.1 M
D.	0.01 M
Answer» D. 0.01 M

Discussion

35.	What is the gas pressure of SF for a compressed gas insulated cable?
A.	10 20 mm Hg
B.	80 100 mm Hg
C.	3 5 kg / cm
D.	40 50 kg / cm
Answer» D. 40 50 kg / cm

Discussion

36.	Steel poles are painted so as to prevent it from ____________.
A.	Corrosion
B.	Borer
C.	Termites
D.	All of these
Answer» B. Borer

Discussion

37.	Assertion (A): The maximum operating temperature of overhead line conductors made of aluminium or copper is restricted to 75 C.Reason (R): conductors beyond this limit may shatter the insulator.
A.	Both A and R are true and R is the correct explanation of A
B.	Both A and R are true and R is not the explanation of A
C.	A is true but R is false
D.	A is false but R is true.
Answer» D. A is false but R is true.

Discussion

38.	In the following graph which curve represents the sag?
A.	I
B.	II
C.	III
D.	IV
Answer» B. II

Discussion

39.	A transmission line has a span of 250 metres between the line supports. The conductors has a cross sectional area of 1.29 cm and weighs 1170 kg/km and has a breaking stress of 4218 kg/cm. Calculate the sag and vertical sag with a safety factor of 5, with a wind pressure of 122 kg per square metre of the projected area.
A.	14 and 5.37
B.	16 and 8.39
C.	14 and 8.39
D.	15 and 5.37
Answer» D. 15 and 5.37

Discussion

40.	3 wire dc distribution system is preferred over 2 wire dc distribution system.the 3 wire dc system of distribution is more safe.
A.	Both A and R are true and R is the correct explanation of A
B.	Both A and R are true and R is not the explanation of A
C.	A is true but R is false
D.	A is false but R is true
Answer» D. A is false but R is true

Discussion

41.	Transmission of electrical power by dc is economical than that with ac. In case of dc transmission, there is no charging current which contributes to the continuous load, even on no load.
A.	Both A and R are true and R is the correct explanation of A
B.	Both A and R are true and R is not the explanation of A
C.	A is true but R is false
D.	A is false but R is true
Answer» C. A is true but R is false

Discussion

42.	In the following graph what does the straight line represent?.
A.	Relation between annual charge and the area of cross section.
B.	Relation between annual cost of energy wasted and area of cross section.
C.	Both (a) and (b).
D.	None of these.
Answer» B. Relation between annual cost of energy wasted and area of cross section.

Discussion

43.	In the following graph what does curve 2 represent?.
A.	Relation between annual charge and the area of cross section.
B.	Relation between annual cost of energy wasted and area of cross section.
C.	Both (a) and (b).
D.	None of these.
Answer» C. Both (a) and (b).

Discussion

44.	What does the point P refer to?.
A.	Most economical power transmission.
B.	Most economical area of cross section.
C.	Both (a) and (b).
D.	Most ideal point of transmission.
Answer» C. Both (a) and (b).

Discussion

45.	The following materials of line conductor are given.
A.	a. i, ii, iv, iii.
B.	B. ii, i, iv, iii.
C.	C. ii, i, iii, iv.
D.	D. i, ii, iii, iv.
Answer» E.

Discussion

46.	Which line represents the tension in the given graph?
A.	I
B.	II
C.	III
D.	IV
Answer» C. III

Discussion

47.	What is the total resistance in a single phase or 2 wire dc line?
A.	Equal to the resistance of either conductor
B.	Double the resistance of either conductor
C.	Half of the resistance of either conductor
D.	None of these
Answer» C. Half of the resistance of either conductor

Discussion

48.	What is the main advantage of ring main system over radial system?i. Voltage drop in the feeder is less.ii. Power factor is higher.iii. Supply is more reliable.Which among the above statements are correct?
A.	i and ii only
B.	ii and iii only
C.	i and iii only
D.	i, ii and iii
Answer» D. i, ii and iii

Discussion

49.	A distribution system is shown in figure with load currents as marked. The two ends of the feeder are fed by voltage sources such that V = V = 3 V, the value of the voltage V for a minimum voltage of 220 V at any point along the feeder is
A.	225.89 V
B.	222.89 V
C.	220.0 V
D.	228.58 V
Answer» B. 222.89 V

Discussion

50.	What is the total charging current per phase for a 33 kV, 50 Hz, 3 phase underground cable of 4 km length using 3 single core cables?Each conductor has a diameter of 2.5 cm and the radial thickness of insulation is 0.5 cm.
A.	15.28 A
B.	11.87 A
C.	13.85 A
D.	8.25 A
Answer» C. 13.85 A

Discussion

Explore topic-wise MCQs in Electrical Engineering (MCQ) questions and answers.

The cost of material used in a distribution circuit per kVA of the distributed power varies as

What will be the pd at point B if a pd of 300 V is maintained at a point A, for a 2 wire dc distributor cable AB if 2 km long and supplies loads of 100A, 150A, 200A, and 50A suited at 500m, 1000m, 1600m, and 2000m from the feeding point A. Each conductor has a resistance of 0.01 per 1000 m.

What is the loss factor in a distribution system?

A 2 wire dc street mains AB, 600 m long is fed from both ends at 220 V. Loads of 20 A, 40 A, 50 A and 30 A are tapped at distances 100m, 250m, 400m and 500m from the end A. If the area of cross section of distributor is 1 cm, what will be the minimum consumer voltage? If ? = 1.7 * 10 cm.

Installation of capacitors at suitable locations and of optimum size in a distribution system results ini. Improved voltage regulation.ii. Reduction in distribution power losses.iii. Reduction of kVA rating of distribution transformers.Which among the above statements are correct?

A 300m ring distributor has loads as shown in the fig. The distances are in metres. The resistance of each conductor is 0.2 W per 1000 metres and loads are tapped off at B, C, D. If the distributor is fed at A at 240 V, what will be the voltage at B?

In a balanced 3 phase, 4 wire ac system the phase sequence is RYB. If the voltage of R phase = 230 0 volts, then what will be the B phase?

A single phase AC distributor supplies two single phase loads as shown. What is the voltage drop from A to C?

Strain and Shackle type insulators are provided on which type of plane?

Assertion (A): Glazing on ceramic insulators is done to make it smooth and non absorbent.Reason (R): Moisture from atmosphere collects on the surface causing electrical breakdown.

Assertion (A): The string efficiency can be improved by using long cross arms.Reason (R): Use of long cross arms reduces the ratio of capacity to earth to capacity per insulator thereby increasing the string efficiency.

Assertion (A): Capacitance grading improves the string efficiency not more than 220 kV.Reason (R): In capacitance grading the units used are of different capacitance and so are not interchangeable.

Which of the following statements are true related to corona?

Corona loss can be reduced by using

By what factor does the critical disruptive voltage (V) get reduced?

Skin effect is negligible for what supply frequency and for what diameter?

Find the spacing between the conductors a 132 kV 3 phase line with 1.956 cm diameter conductors is built so that corona takes place, if the line voltage exceeds 210 kV (rms). With g = 30 kV/cm.

Skin effect in a conductor is proportional to

Assertion (A): Transposition of conductors in a transmission line is necessary.Reason (R): Corona losses are reduced by transposition of conductors.

What is the charging current per km for the transmission line shown in the figure. Operating at 132 kV, the conductor diameter is 0.8 cm.

A three phase, 50Hz transmission line consists of three equal conductors of radii r placed in a horizontal plane with a spacing of 6m between middle and outer conductor. If the radius of each conductor is 12.5 mm, then inductance per phase per km of the transposed line will be

What is the inductance per phase per km of a double circuit 3 phase line as shown in the fig. The conductors are transposed and are of radius 0.75 cm each.

Assertion (A): the concept of GMD is applicable for the calculation of inductance of transmission lines.Reason (R): The radius of the conductor of transmission lines, in the expression for inductance is not the self GMD of the conductor.

Capacitance between the two conductors of a single phase two wire line is 0.5 F/km. What is the value of capacitance of each conductor to neutral?

What is the line length if a load of 15000 kW at a power factor 0.8 lagging can be delivered by a 3 phase transmission line having conductors each of resistance 1 per kilometre? The voltage at the receiving end is to be 132kV and the loss is about 5%.

The ABCD constants of a 3 phase transposed transmission line with linear and passive elements ________________.

What are the A and D parameters in case of medium transmission line (nominal T method)?

What is the value of the C parameter by using a nominal T method for a 3 phase balanced load of 30 MW which is supplied by a 132 kV, 50 Hz and 0.85 pf lagging? The series impedance of a single conductor is (20 + j52) and the total phase to neutral admittance is 315 * 10 siemen.

What is the limit of the conductor cross section when paper insulation is used?

The ABCD parameter of a 3 phase transmission line is given as followsA = D = 0.8 1 , B = 170 85 , and C = 0.002 90.4 the sending end voltage is 400 kV. What is the receiving end voltage under no load condition?

Correctly match the items in List 1 to the items in List 2: List 1List 2Codes:

The insulation resistance of a cable of length 10 km is 1M . For a length of 100 km of the same cable, what will be the insulation resistance?

What is the gas pressure of SF for a compressed gas insulated cable?

Steel poles are painted so as to prevent it from ____________.

Assertion (A): The maximum operating temperature of overhead line conductors made of aluminium or copper is restricted to 75 C.Reason (R): conductors beyond this limit may shatter the insulator.

In the following graph which curve represents the sag?

3 wire dc distribution system is preferred over 2 wire dc distribution system.the 3 wire dc system of distribution is more safe.

Transmission of electrical power by dc is economical than that with ac. In case of dc transmission, there is no charging current which contributes to the continuous load, even on no load.

In the following graph what does the straight line represent?.

In the following graph what does curve 2 represent?.

What does the point P refer to?.

The following materials of line conductor are given.

Which line represents the tension in the given graph?

What is the total resistance in a single phase or 2 wire dc line?

What is the main advantage of ring main system over radial system?i. Voltage drop in the feeder is less.ii. Power factor is higher.iii. Supply is more reliable.Which among the above statements are correct?

A distribution system is shown in figure with load currents as marked. The two ends of the feeder are fed by voltage sources such that V = V = 3 V, the value of the voltage V for a minimum voltage of 220 V at any point along the feeder is

What is the total charging current per phase for a 33 kV, 50 Hz, 3 phase underground cable of 4 km length using 3 single core cables?Each conductor has a diameter of 2.5 cm and the radial thickness of insulation is 0.5 cm.