## electrical

### Transmission and Distribution MCQ Objective Questions and Answers Page - 5

1.
 To increase the transmission capability of a high voltage long line A The resistance can be increased B The resistance can be decreased C The series reactance can be reduced D The shunt admittance can be reduced Answer : C Explanation :
2.
 Power despatch through a line can be increased by A Installing series capacitors B Installing shunt capacitors C Installing series reactor D Installing shunt reactor Answer : A Explanation :
3.
 The power transmitted will be maximum when A Line reactance is high B Corona losses are minimum C Sending end voltage is more D Receiving end voltage is more Answer : D Explanation :
4.
 For constant voltage transmission, the voltage drop along the line is maintained constant by installing A Capacitors B Inductors C Resistors D Synchronous phase modifiers at receiving end Answer : D Explanation :
5.
 Constant voltage transmission have the drawback(s) of A Increase of short-circuit current of the system. B Lower reserve of lines in case of line trouble. C Increased risk of interruption of supply due to falling of synchronous motors out of synchronism. D All of the above Answer : D Explanation :
6.
 Constant voltage transmission have the advantage(s) of A Availability of steady voltage at all loads at the receiving end. B Possibility of better protection for the line due to possible use of higher terminal reactances. C Possibility of carrying increased power for a given conductor size in case of long distance heavy power transmission. D All of the above. Answer : D Explanation :
7.
 Constant voltage transmission have the advantage(s) of A Increase of short-circuit current of the system. B Large reserve of lines in case of line trouble. C Improvement of power factor at the times of modeeate and heavy loads. D All of the above. Answer : C Explanation :
8.
 When the sending end voltage and current are numerically equal to the receiving end voltage and current respectively, then the line is called A A tuned line B A transposed line C A long line D A short line Answer : A Explanation :
9.
 A synchronous conductor is a A Synchronous generator B Paper condenser C Synchronous motor D None of these Answer : C Explanation :
10.
 A synchronous compensator absorbs inductive reactive power. It is A Overexcited B Normally excited C Underexcited D None of these Answer : C Explanation :
11.
 A synchronous phase modifier as compared to synchronous motor of the same rating has A Larger shaft diameter and higher speed. B Smaller shaft diameter and higher speed. C Larger shaft diameter and Smaller speed. D Smaller shaft diameter and Smaller speed. Answer : B Explanation :
12.
 Phase modifier is normally installed in case of A Short transmission lines B Medium length lines C Long lines D For any length of lines Answer : C Explanation :
13.
 Which of the following statements is not true  ? A Synchronous phase modifiers are installed at sending end. B Synchronous phase modifiers are installed at load end. C Synchronous phase modifiers are nothing but Synchronous motors (specially designed). D Synchronous phase modifiers do not carry load. Answer : A Explanation :
14.
 Capacitors are used in power system to A Improve supply power factor. B Improve voltage regulation. C Change the load characteristics D All  of the above Answer : B Explanation :
15.
 Series capacitors on transmission lines are of little use when A The load  VAR requirement is small. B The load  VAR requirement is large. C The load  VAR requirement is fluctuating. D Series capacitors are never used in transmission lines. Answer : A Explanation :
16.
 For a fixed value of complex power flow in a transmission line having a sending end voltage  V, the real power loss loss will be proportional to A V B $V^{2}$ C $\frac{1}{V^{2}}$ D $\frac{1}{V}$ Answer : C Explanation :
17.
 For a fixed receiving-end and sending-end voltages in a transmission system, what is the locus of the constant power  ? A A straight line B An ellipse C A parabola D A circle Answer : D Explanation :
18.
 Conduit pipe is generally employed for protection of A Unsheathed cables B Armoured cables C PVC sheathed cables D All of the above Answer : A Explanation :
19.
 Sheaths are used in cables to A Provide proper insulation B Provide mechanical strength C Prevent ingress of moisture D None of the above Answer : C Explanation :
20.
 The bedding  on a cable consists of A Jute strands B Hessian tape C Paper tape compounded with a fiberous material D Any of the above Answer : D Explanation :
21.
 The material(s) used for armouring of an underground cable  is/are A Galvanised steel wire B Steel tape C Aluminium D Wither (a)  or  (b) Answer : D Explanation :
22.
 Metallic shielding is provided on underground cable to A Reduce thermal resistance B Reduce corona effect C Control the electrostatic voltage stress D All of the above Answer : D Explanation :
23.
 Metallic shielding provided on cables is usually of thickness. A 0.1 – 0.8 mm B 3 – 5 mm C 10 – 15 mm D 15 – 25  mm Answer : B Explanation :
24.
 The effect of bonding the cable is A To increase the effective resistance and inductance B To increase the effective resistance but reduce inductance C To reduce the effective resistance and inductance D To reduce the effective resistance but increase the inductance Answer : B Explanation :
25.
 The thickness of insulation layer provided on the conductor, in cables, depends upon A Operating voltage B Current to be carried C Power factor D Both (a) and (b) Answer : A Explanation :
26.
 The undesirable property of an electrical insulating material is A High dielectric strength B High relative permittivity C High thermal conductivity D High insulation resistivity Answer : B Explanation :
27.
 Empire tape is A Varnished cambric B Impregnated paper C Vulcanised rubber D Enamel insulation Answer : A Explanation :
28.
 Paper as an insulating material has the main drawback that it A Is hygroscopic B Has poor dielectric strength C Has low insulation resistivity D Has high capacitance Answer : A Explanation :
29.
 In paper insulated cables, the conductor x-section is usually limited to A $50&space;mm^{2}$ B $250&space;mm^{2}$ C $600&space;mm^{2}$ D $1200&space;mm^{2}$ Answer : C Explanation :
30.
 The dielectric strength of impregnated paper is about A 30 kV/mm B 20 kV/mm C 15 kV/mm D 5 kV/mm Answer : A Explanation :
31.
 Paper used as an insulating material is usually treated with oily compound because it A Is hygroscopic B Gets electrostatically charged at high voltage C Is porous D All of the above Answer : B Explanation :
32.
 Single-core cables are usually not provided with armouring in order to A Avoid excessive loss in the armour B Make the cable more flexible C Make the cable non-hygroscopic D None of the above Answer : A Explanation :
33.
 Multi-core cables generally use A Oval shaped conductors B Sector shaped conductors C Square conductors D Either (a) or (b) Answer : D Explanation :
34.
 SL type cables, over H-type cables, have the advantage(s) of A Possibility of bending of cables owing to no overall lead sheath. B Less tendency for oil drainage on hilly routes owing to elimination of filler spaces containing compound. C Easy manufacturing. D Both (a) and (b) Answer : D Explanation :
35.
 Screened type cables, over belted cables, have the advantage(s) of A Reduced possibility of core to core faults. B Uniform radial electric stresses in all sections of the dielectric. C No possibility of formation of voids within the dielectric. D All of the above. Answer : D Explanation :
36.
 Solid type cables are not considered suitable for operating voltages exceeding  66 kV  because A Skin effect dominates on the conductor. B There is a danger of breakdown of insulation because of formation of voids in the layers of dielectric. C There is a corona loss between conductor and sheath material. D Insulation may melt due to heating. Answer : B Explanation :
37.
 In a 3-core extra high voltage cable, a metallic screen around each core insulation is provided to A Facilitate heat dissipation. B Give mechanical strength. C Obtain radial electric stress. D Obtain longitudinal electric stress. Answer : C Explanation :
38.
 Oil-filled cables have the advantage(s) of A No ionisation, oxidation and formation of voids. B Possibility of increased temperature range in service. C More maximum permissible stresses. D All of the above. Answer : D Explanation :
39.
 Oil-filled cables have the advantage(s) of A Small overall size. B Most perfect impregnation. C Easy detection of fault. D All of the above Answer : D Explanation :
40.
 Oil-filled cables have the drawback(s) of A No possibility of impregnation after sheathing. B Greater cost and complicated laying of cables and maintenance. C High thermal resistance. D All of the above Answer : B Explanation :