## electrical

### Transmission and Distribution MCQ Objective Questions and Answers Page - 1

1.
 Transmission line connects A Generating station to a switching station/step-down transformer station. B Step-down transformer station to service transformer banks. C Distribution transformer to consumer premises. D Service points to consumer premises. Answer : A Explanation :
2.
 A 3-phase 4-wire system is commonly used for A Primary Distribution B Secondary Distribution C Primary Transmission D Secondary Transmission Answer : B Explanation :
3.
 The rated voltage of a 3-phase power is given as A RMS phase voltage B Peak phase voltage C RMS line  to  line voltage D Peak line  to  line voltage Answer : C Explanation :
4.
 Which of the following is usually not the generating voltage  ? A 6.6 kV B 9.9 kV C 11 kV D 13.2 kV Answer : B Explanation :
5.
 In a Transmission system the feeder supplies power to A Transformer substations (step-up) B Service mains C Distributors D All of the above Answer : C Explanation :
6.
 Feeder is designed mainly from the point of view of A Its current carrying capacity B Voltage drop in it C Operating voltage D Operating frequency Answer : A Explanation :
7.
 Distributors are designed from the point of view of A Its current carrying capacity B Operating voltage C Voltage drop in it D Operating frequency Answer : C Explanation :
8.
 Transmission and Distribution of electric power by underground system is superior to overhead system in respect of A Appearance and public safety B Maintenance cost C Frequency of faults, power failure and accidents D All of the above Answer : D Explanation :
9.
 The main drawback(s) of underground system over overhead system  is/are A Exposure to lightning B Heavy initial cost C Exposure to atmospheric hazards such as smoke, ice, wind etc. D Inductive interference between power and communication circuits. Answer : B Explanation :
10.
 The main drawback(s) of overhead system over underground system  is/are A Underground system is more flexible than overhead system B Higher charging current C Surge problem D High initial cost Answer : C Explanation :
11.
 By increasing the Transmission voltage double of its original value, the same power can be despatched keeping the line loss A Equal to  its original value B Half of original value C Double the original value D One-fourth of original value Answer : D Explanation :
12.
 For the same voltage drop increasing the voltage of a distributor  n-times A Reduce the  x-section  of the conductor by  n  times B Increases the x-section  of the conductor by  n  times C Reduce the  x-section  of the conductor by  n2  times D Increases the x-section  of the conductor by  n2  times Answer : A Explanation :
13.
 In a Transmission system, the weight of copper used is proportional to A $E^{2}$ B E C $\frac{1}{E^{2}}$ D $\frac{1}{E}$ Answer : C Explanation :
14.
 The volume of copper required for an ac Transmission line is inversely proportional to A Current B Voltage C Pf D Both (b) and (c) Answer : D Explanation :
15.
 For the same conductor length, same amount of power, same losses and same maximum voltage to earth, which system required minimum conductor area  ? A Single-phase ac B 3-phase ac C 2-wire ac D 3-wire dc Answer : D Explanation :
16.
 Which of the following distribution system is preferred for good efficiency and high economy  ? A Single-phase, 2-wire system B 2- phase, 3-wire system C 3- phase, 3-wire system D 3- phase, 4-wire system Answer : D Explanation :
17.
 The approximate cost ratio of a  220 kV , underground cable transmission and  220 kV O/H transmission is A 50 B 25 C 13 D 5 Answer : C Explanation :
18.
 The main reason for using high voltage for long distance power transmission is A Reduction in transmission losses. B Reduction in time of transmission. C Increase in system reliability D None of the above Answer : A Explanation :
19.
 66 kV is suitable for transmission of power over A 30 km B 60 km C 120 km D 200 km Answer : B Explanation :
20.
 If  3 MW  power is to be transmitted over a distance of  30 km,  the desirable transmission voltage will be A 11 kV B 33 kV C 66 kV D 3.3 kV Answer : B Explanation :
21.
 The highest transmission voltage used in India is A 400 kV B 220 kV C 132 kV D 765 kV Answer : D Explanation :
22.
 If variable part of annual cost on account of interest and depreciation on the capital out lay is equal to the annual cost of electrical energy wasted in the conductors, the total annual cost will be minimum and the corresponding size of conductor will be the most economical. This statement is known as A Lenz’s Law B Kelvin’s Law C Faraday’s Law D Ohm’s Law Answer : B Explanation :
23.
 For high-voltage transmission lines, conductors are suspended from towers so as to A Increase clearance from ground B Reduce clearance from ground C Take care of increase in length D Reduce wind and snow effects Answer : A Explanation :
24.
 The supports used for transmission lines should have the characteristic(s)  of A High mechanical strength and longer life. B Good looking, light in weight and easily accessible for painting and erection of line conductors. C Cheap in initial as well in maintenance cost. D All of the above Answer : D Explanation :
25.
 The wooden poles well impregnated with creosote oil or any preservative compound have life of A 25 – 30 years B 20 – 25 years C 10 – 15 years D 5 – 10 years Answer : A Explanation :
26.
 Steel poles for transmission lines need protection against A Borer B Termites C Corrosion D All of these Answer : C Explanation :
27.
 RCC poles usually have the spans of A 250 – 400 m B 80 – 150 m C 50 – 80 m D 25 – 50 m Answer : B Explanation :
28.
 In India for distribution of electric power we usually use A Wooden poles B Steel poles C RCC poles D Both (b) and (c) Answer : D Explanation :
29.
 Conductors used in  ht  transmission lines are stranded because of A Increased tensile strength B Ease in handling C Cheaper in cost D Reduced resistivity Answer : B Explanation :
30.
 Which of the following properties has got higher value for aluminium in comparison to that of copper  ? A Electrical resistivity B Melting point C Thermal conductivity D Specific gravity Answer : A Explanation :
31.
 In a  7/30  ACSR conductor why is grease put between steel and aluminium conductors  ? A To reduce corrosion by electrolytic action between zinc  (galvanising agent on steel) and aluminium. B To reduce friction between the strands. C To reduce leakage of current from aluminium strands to steel strands. D To eliminate air pockets. Answer : A Explanation :
32.
 ACSR is used in place of copper in overhead lines because of A Higher current carrying capacity B Being lighter in weight C Economy D Higher tensile strength Answer : C Explanation :
33.
 ACSR conductors have A All conductors made of aluminium. B Outer conductors made of aluminium. C Inner conductors made of aluminium. D No conductors made of aluminium. Answer : B Explanation :
34.
 The function of steel wire in an  ACSR  conductor is to A Compensate for skin effect. B Take care of surges. C Provide additional mechanical strength. D Reduce inductance. Answer : C Explanation :
35.
 The material used for the manufacture of ground wire is A Aluminium B Galvanised steel C Cast iron D Stainless steel Answer : B Explanation :
36.
 Guy wire is employed for A Providing protection against surges B Providing emergency earth route C Supporting the pole D All of the above Answer : C Explanation :
37.
 The sag of a transmission line is least affected owing to A Weight of the conductor B Current through the conductor C Atmospheric temperature D Ice deposition on the conductor Answer : B Explanation :
38.
 Effect of temperature rise in overhead lines is to A Increase the sag and decrease the tension B Decrease the sag and increase the tension C Increase both D Decrease both Answer : A Explanation :
39.
 In a transmission line, sag depends upon A Span length B Tension in conductors C Weight of the conductor per unit length D All of the above Answer : D Explanation :
40.
 Which of the following statements is correct  ? A Ice on conductors increases skin effect. B Wind pressure reduces corona effect. C Wind pressure is taken to act at perpendicular to that for ice. D Ice on conductors reduces sag. Answer : C Explanation :
41.
 By which of the following system electric power may be transmitted? A Overhead system B Underground system C Both (a) and (b) D None of the above Answer : C Explanation :
42.
 ____________   are the conductors, which connect the consumer’s terminal to the distribution? A Distributor B Service main C Feeders D None of the above Answer : B Explanation :
43.
 The underground system cannot be operated above A 440 V B 11kv C 33KV D 66 kV Answer : D Explanation :
44.
 Overhead system can be designed for operation upto A 11 KV B 33kV C 66kV D 400kV Answer : D Explanation :
45.
 If variable part of annual cost on account of interest and depreciation on the capital outlay is equal to the annual cost of electrical energy wasted in the conductor, the total annual cost of electric energy wasted in the conductor, the total annual cost will be minimum and the corresponding size of conductor will be most economical. This statement is known as A Kelvin’s law B Ohm’s law C Kirchhoff’s law D Faraday’s law Answer : A Explanation :
46.
 The wooden poles well impregnated with creosote oil or any preservative compound have life A From 2 to 5 year B 10 to 15 years C 25 to 30 years D 60 to 70 year Answer : C Explanation :
47.
 Which of the following materials is not used for transmission and distribution of electrical power? A Copper B Aluminium C Steel D Tungsten Answer : D Explanation :
48.
 Galvanised steel wire is generally used as A Stay wire B Earth wire C Structural component D All of the above Answer : D Explanation :
49.
 The usual spans with R.C.C poles are A 40 to 50 metres B 60-100 metres C 80-100 metres D 300-500 metres Answer : C Explanation :
50.
 The corona is considerably affected by which of the following? A Size of the conductor B Shape of the conductor C Surface condition of the conductor D All of the above Answer : D Explanation :
51.
 % age regulation of a transmission line is given by A (Vr-Vs)/Vr² x 100 B (Vr-Vs)/Vr x 100 C (Vs-Vr)/Vs x 100 D (Vs-Vr)/Vr² x 100 Answer : B Explanation :