## electrical

### Transmission and Distribution MCQ Objective Questions and Answers Page - 7

1.
 In a distribution system, which of the following items shares the major cost  ? A Conductors B Earthing system C Distribution transformer D Insulators Answer : C Explanation :
2.
 The distribution in residential areas are A Single phase, two-wire B Three phase, three-wire C Three phase, four-wire D Two phase, four-wire Answer : C Explanation :
3.
 The loads on 3-phase, 4-wire distribution are usually A Balanced B Unbalanced C Either of above D None of above Answer : B Explanation :
4.
 A uniformly loaded dc distributor is fed at both ends with equal voltages. In comparison to a similar distributor fed at one end only, the maximum voltage drop will be A One-fourth B One-half C One-third D One-sixth Answer : A Explanation :
5.
 The null point of a uniformly loaded distributor fed at equal voltage at both ends lies at A Midpoint B Either end C Two-third distance from one end D One-fourth distance from one end Answer : A Explanation :
6.
 A uniformly loaded dc distributor is fed at both ends with equal voltages. In comparison to a similar distributor fed at one end only, the drop at the mid point will be A One-fourth B One-half C One-third D One-sixth Answer : C Explanation :
7.
 When 7/o.o29 VIR cable is carrying  20 A, a drop of  1 V occurs every  12 m. the voltage drop in a  100 m  run of this cable when it is carrying  10 A  is nearly A 4.2 V B 3.2 V C 1.2 V D 0.42 V Answer : A Explanation :
8.
 In a dc 3-wire distributor using balancers and having unequal loads on the two sides A Both balancers operate as generators B Both balancers operate as motors C Balancer connected to lightly loaded side operates as a generator D Balancer connected to heavily loaded side operates as a generator Answer : D Explanation :
9.
 In a dc 3-wire distribution system, balancer fields are cross-connected in order to A Equalise voltages on  +ve  and  -ve  outers. B Boost the generated voltage. C Make both machines operated as unloaded motors. D All of the above Answer : A Explanation :
10.
 The booster A Is a series wound dc generator driven by dc shunt motor. B Is a low voltage and high current generator operating on straight or linear portion of its voltage-current characteristic. C Is a high voltage and low circuit machine. D Both (a) and (b) Answer : D Explanation :
11.
 The booster is inserted in the circuit to A Reduce current B Increase current C Reduce voltage drop D Compensate for voltage drop Answer : D Explanation :
12.
 In order to reduce the inductive interference to parallel communication circuits to the minimum. A The conductors are transposed at regular intervals. B Bundle conductors are used. C Thick conductors are used. D Either (a) or (b) Answer : D Explanation :
13.
 Bundled conductors are used for  EHV  transmission lines primarily for reducing the A Corona loss B Surge impedance of the line C Voltage drop across the line D $I^{2}&space;R$  losses Answer : A Explanation :
14.
 The conductor of an EHV line is selected on the basis of A Current carrying capacity B Corona and RI performance C Line voltage D None of these Answer : B Explanation :
15.
 Frequency of resonant vibrations lies in the range of A 10-20 Hz B 100-200 Hz C 50-100 Hz D 200-300 Hz Answer : C Explanation :
16.
 On what basis is the insulation level of a  400 kV, EHV  overhead transmission line decided  ? A Lightning overvoltage B Corona inception voltage C Switching overvoltage D Radio and TV interference Answer : C Explanation :
17.
 A surge impedance of  10 kV  travels along a cable towards its junction with an overhead line. The surge impedance of the cable and the lines are  50 Ω  and  450 Ω,  respectively. the surge voltage transmitted into the line is A 18.0 kV B 4.0 kV C 20.0 kV D 2.0 kV Answer : A Explanation :
18.
 Series capacitor is used in a transmission line to A Compensate the voltage drop B Reduce line loss C Limit short-circuit current D Improve load power factor Answer : A Explanation :
19.
 Series capacitive compensation in EHV transmission lines is used to A Reduce the line loading B Improve the stability of the system C Reduce the voltage profile D Improve the protection of the line Answer : B Explanation :
20.
 Series capacitors can be used in distribution lines A To provide reactive power compensation B To reduce the receiving-end voltage under light load conditions C To reduce the voltage drop D To reduce line losses Answer : A Explanation :
21.
 Shunt compensation in an EHV line is used to improve A Stability and fault level B Fault level and voltage profile C Voltage profile and stability D Stability, fault level and voltage profile Answer : C Explanation :
22.
 The most accurate and versatile method of achieving reactive power compensation is using A Switched capacitors B Fixe capacitor with controlled reactor C Saturable reactor with capacitor bank D Switched capacitor with controlled reactors Answer : D Explanation :
23.
 Shunt reactors are sometimes used in high voltage transmission system to A Limit the short circuit current through the line B Compensate for the series reactance of the line under heavily  loaded condition C Limit over voltages at the load side under lightly loaded condition D Compensate for the voltage drop in the under heavily loaded condition Answer : C Explanation :
24.
 Insulation coordination for UHV lines (above 500 kV) is done based on A Lightning  surges B Lightning  surges and switching surges C Switching surges D None of the above Answer : C Explanation :
25.
 At an industrial substation with a MW load, a capacitor of 2 MVAR is installed to maintain the load power factor at  0.97  lagging. If the capacitor goes out of service, the load power factor becomes A 0.85 B 1.00 C 0.80 lag D 0.90 lag Answer : C Explanation :
26.
 For enhancing the power transmission in a long  EHV  transmission line, the most preferred method is to connect a A Series inductive compensator in the line. B Shunt inductive compensator at the receiving end. C Series capacitive compensator in the line. D Shunt capacitive compensator at the sending end. Answer : C Explanation :
27.
 A lossless transmission line having Surge Impedance Loading (SIL)  of  2280 MW  is provided with a uniformly distributed series capacitive compensation of  30%. Then, SIL of the compensated transmission line will be A 1835 MW B 2280 MW C 2725 MW D 3257 MW Answer : C Explanation :
28.
 The following is not an advantage of dc transmission  : A No charging current B No skin effect C No stability problem D Cheap converters Answer : D Explanation :
29.
 In an HVDC system  : A Both generation and distribution are dc. B Generation is ac and distribution is dc. C Generation is dc and distribution is ac. D Both generation and distribution are ac. Answer : D Explanation :
30.
 In a dc transmission line A It is necessary for the sending end and receiving end to be operated in synchronism. B The effects of inductive and capacitive reactance’s are greater than in an ac transmission line of the same rating. C There are no effects due to inductive and capacitive and capacitive reactance’s. D Power transfer capability is limited by stability considerations. Answer : C Explanation :
31.
 High Voltage DC (HVDC) transmission is mainly used for A Bulk power transmission over very long distances. B Interconnecting two system with the same nominal frequency. C Eliminating reactive power requirement in the operation. D Minimizing harmonics at the converter stations. Answer : A Explanation :
32.
 Bulk power transmission over long High Voltage DC lines is preferred because of A Low cost of HVDC terminal. B No harmonic losses. C Minimum line power losses. D Simple protection. Answer : C Explanation :
33.
 In the case of an HVDC system, there is A Charging current but no skin effect. B No Charging current but skin effect. C Neither Charging current nor skin effect. D Both Charging current and skin effect. Answer : C Explanation :
34.
 Which one of the following statements in respect of High Voltage DC transmission line is not correct  ? A The power transmission capability of bipolar lines is almost the same as that of single circuit ac line. B HVDC link can operate between ac system whose frequency need not be equal. C There is no distance limitation for HVDC transmission by UG cable. D Corona loss is much higher in HVDC transmission line. Answer : D Explanation :
35.
 The power transmission capability of bipolar lines is approximately A Half that of 3-phase single circuit. B Same as that 3-phase single circuit line. C Twice that of 3-phase single circuit line. D Thrice that of 3-phase single circuit line. Answer : B Explanation :
36.
 The method used to implement an asynchronous link is A Dc back to back connected converter B 0-3600  static phase shifter C Rotary transformer D Static VAR compensator Answer : A Explanation :
37.
 High Voltage DC monopolar link use A One conductor usually of negative polarity B One conductor usually of positive polarity C Two conductor one of positive and the other of negative polarity D Two conductors both of negative polarity Answer : A Explanation :
38.
 Back to back High Voltage DC is used to A Increase the transmission capability B Decrease line losses C Provide stable interconnection D Reduce voltage drop Answer : C Explanation :
39.
 Which of the following will be provided to reduce the harmonics on ac side of an HVDC transmission line  ? A Synchronous motors in over excited condition. B Shunt capacitor. C Static compensator. D Shunt filters. Answer : D Explanation :
40.
 In HVDC transmission there are predominant A Voltage harmonics on dc side and Current harmonics on ac side of converters. B Current harmonics on dc side and Voltage harmonics on ac side of converters. C Current harmonics only on the dc side of converters. D Voltage harmonics only on the ac side of converters. Answer : A Explanation :
41.
 The steel used in steel cored conductors is usually A Alloy steel B Stainless steel C Mild steel D High speed steel Answer : C Explanation :
42.
 Which of the following distribution systems is more reliable? A Radial system B Tree system C Ring main system D All are equally reliable Answer : C Explanation :
43.
 Which of the following characteristics should the line support for transmission lines possess? A Low cost B High mechanical strength C Longer life D All of the above Answer : D Explanation :
44.
 Transmission voltage of 11 kV is normally used for distances upto A 20 – 25 km B 40 – 50 km C 60 – 70 km D 80 – 100 km Answer : A Explanation :
45.
 Which of the following regulations is considered best? A 50 % B 20 % C 10 % D 2 % Answer : D Explanation :
46.
 A conductor, due to sag between two supports, takes the form of A Semi-circle B Triangle C Ellipse D Catenary Answer : D Explanation :
47.
 In A.C.S.R.  conductors, the insulation between aluminium and steel conductors is A Insulin B Bitumen C Varnish D No insulation is required Answer : D Explanation :
48.
 Which of the following bus-bar schemes has the lowest cost? A Ring bus-bar scheme B Single bus-bar scheme C Breaker and a half scheme D Main and transfer scheme Answer : B Explanation :
49.
 Owing to skin effect A Current flows through the half cross-section of the conductor B Portion of the conductor near to surface carries more current and core of the conductor carries less current C Portion of the conductor near to surface carries less current and core of the conductor carries more current D Any of the above Answer : B Explanation :