## electrical

### Transmission and Distribution MCQ Objective Questions and Answers Page - 8

1.
 High voltage dc transmission requires filters for A Current harmonics on ac side and voltage harmonics on dc side. B Voltage harmonics on ac side and Current harmonics on dc side. C Voltage harmonics on both ac and dc sides. D Current harmonics on both ac and dc sides. Answer : B Explanation :
2.
 In a 3-phase bridge rectifier circuit for  HVDC  transmission, the ratio of output dc voltage to input ac voltage is A 0.5 B 1.0 C $\sqrt{3}$ D 2 Answer : D Explanation :
3.
 In HVDC converter station equipment using thyristors it is necessary to use a large number of thyristors in series because A Current ratings of thyristors are low. B Voltage ratings of thyristors are low. C Thyristors always fail to an internal open circuit. D None of the above. Answer : B Explanation :
4.
 In the HVDC  system, the ac harmonics which gets effectively eliminated with 12 pulse bridge converters, are A Triplen harmonics B Triplen and 5th harmonics C Triplen, 5th and 7th harmonics D 5th and 7th harmonics Answer : D Explanation :
5.
 By which of the following method string efficiency can be improved? A Using a guard ring B Grading the insulator C Using long cross arm D Any of the above Answer : D Explanation :
6.
 In aluminium conductors, steel core is provided to A Compensate for skin effect B Neutralise proximity effect C Reduce line inductance D Increase the tensile strength Answer : D Explanation :
7.
 By which of the following a bus-bar is rated? A Current only B Current and voltage C Current, voltage and frequency D Current, voltage, frequency and short time current Answer : D Explanation :
8.
 A circuit is disconnected by isolators when A Line is energized B There is no current in the line C Line is on full load D Circuit breaker is not open Answer : B Explanation :
9.
 For which of the following equipment current rating is not necessary? A Circuit breakers B Isolators C Load break switch D Circuit breakers and load break switches Answer : B Explanation :
10.
 In a substation the following equipment is not installed A Exciters B Series capacitors C Shunt reactors D Voltage transformers Answer : A Explanation :
11.
 Corona usually occurs when the electrostatic stress in air around the conductor exceeds A 6.6 kV (r.m.s. value)/cm B 11 kV (r.m.s. value)/cm C 22 kV (maximum value)/cm D 30 kV (maximum value)/cm Answer : D Explanation :
12.
 The voltage drop, for constant voltage transmission is compensated by installing A Inductors B Capacitors C Synchronous motors D All of above Answer : C Explanation :
13.
 The use of strain type insulators is made where the conductors are A Dead ended B At intermediate anchor towers C Any of the above D None of the above Answer : C Explanation :
14.
 The current drawn by the line due to corona losses is A Non-sinusoidal B Sinusoidal C Triangular D Square Answer : A Explanation :