Electrical Engineering Interview Questions and Answers

1. What is an isolation transformer?
2. Why we don’t use wood as the core for transformers?
3. Why are alternators put in parallel?
4. What do you mean by Switchgear?
5. What do you mean by synchronising of alternator?
6. What is through fault in power system?
7. What is difference between symmetrical and unsymmetrical faults?
8. What are incipient faults in power system?
9. What is booster transformer?
10. What is difference between system earthing and equipment earthing?
11. What is the purpose of using series capacitor in a transmission line?
12. Which device is used to protect the power system against travelling wave?
13. What is a teaser transformer?
14. What is flyback transformer?
15. How does a direct current transformer work?
16. What do meant by 100kVA transformer?
17. Is lightning AC or DC?
18. What is the purpose of zero-ohm resistance?
19. Can a 60Hz transformer work on a 50Hz system? Why?

20. How does Transformer efficiency changes as load increases?
21. What is the condition to obtain maximum efficiency in a single-phase transformer?
22. Why don’t transformers work with a DC supply?
23. What do you mean by Earth electrode?
24. What do you mean by earthing mat?
25. What is system grounding?
26. What is neutral grounding?
27. What is Arcing ground?
28. What do you mean by earthing mat?
29. What are the various methods of neutral grounding?
30. What is an earthing transformer?
31. What is the role of earthing Transformer in neutral grounding?
32. What is arc suppression coil grounding?
33. What are the functions of panels and fire fighting equipment in a substations?
34. List out the equipment used in a substation?
35. Sequence of questions during opening and closing of a substation circuit?
36. What is the need of providing isolator on the supply sides of the circuit breaker?
37. What is difference between primary and secondary batteries?
38. Why the lead acid batteries should not to discharge beyond 1.75 volt?
39. What is difference between AC and DC resistance of a conductor?
40. Define active, reactive and Apparent power ?
41. Name the different types of tariffs?
42. What is the purpose of using bundled conductors in transmission?
43. Why power factor tariff is imposed?

44. What is the purpose of transposition of conductor in three phase transmission line?
45. Why the power factor not more than unity?
46. What is the effect of capacitance on inductive load?
47. What voltage is supplied to the large industrial consumer?
48. Upto what voltage level we can use pin type insulator?
49. What are the transmission voltage that are used in India?
50. What are the major problems associated with EHV transmission?
51. What are the purpose of providing series and shunt compensation in EHV line?
52. What is the providing series compensation in EHV line?
53. What is the purpose of providing shunt capacitor compensation in EHV line?
54. What is series and shunt compensation in transmission line?
55. Why shunt compensation is preferred over series compensation?
56. What are the sources of audible noise generation in EHV transmission system?
57. Why is voltage regulation better in case of DC transmission?
58. Why HVDC line do not require any reactive power compensation?
59. What are the advantages of hvdc transmission system?
60. What are the main feature of directional relay?

61. What is difference between radial and ring main system of distribution?
62. What are the different types of faults which occur in a power system?
63. What is a booster in power system?
64. What are the major problems associated with HVDC circuit breaker?
65. Name the material used for contact of vacuum circuit breaker?
66. What is a protective relay?
67. What is difference between feeder and distributor?
68. Define the term sensitivity and selectivity of a relay?
69. What is meant by operating time of a protective relay?
70. What is Buchholz relay? Which equipment is protected by it?
71. What happens in a transformer when a secondary load exceeds power output?
72. What is the speed of electric current?
73. Why do we use AC supply in our homes?
74. What is the difference between earth resistance and earth electrode resistance?
75. What is the difference between earth resistance and earth electrode resistance?
76. What is the power factor of an alternator at no load?
77. What are the advantage of free wheeling diode in a Full Wave rectifier?
78. How does the resistance of a conductor change with a rise in temperature?
79. What is the meaning of DYN11 in a transformer?
80. What are the applications of wireless power transformer?
81. Why does America use 110V as single phase voltage but Europe and Asia use 230v?
82. Why do we use transformers in electronic and electrical circuits?
83. Why core loss is constant in a transformer?
84. Why do people say that current kills you, not voltage?
85. How do switch-mode transformers function?
86. What is cogging and crawling in machines?
87. What are positive, negative & zero sequence impedance?
88. What is something electrical engineers know that others don’t?
89. What is BDV (Break Down Voltage) Test in transformer?
90. Does fire conduct electricity?
91. What is the working principle of transformers?
92. What is the difference between single phase and three phase?
93. Why CBCT can’t detect phase to phase fault?
94. Why do we use rod gaps across the bushing of a pole-mounted transformer?
95. What is the difference between watts and volts?
96. How capacitor are always connected in parallel?
97. Why are 3-phase induction motors self-starting, but 3-phase synchronous motors are not?
98. Why do we short circuit a current transformer?
99. Why are there only 3-phase electrical power systems? why not 6-phase, 9-phase, 12-phase, or some other number of phases?
100. What would happen if I put my smartphone into the refrigerator?
101. What is a transformer bushing?
102. What is the use of a three winding transformer?
103. What is the difference between the speed and the torque of a motor?
104. Why do bats die of electric shock when hanging from electric wire but not birds?
105. What is the importance of slip in a 3-phase induction motor?
106. What is the necessity of tap changing in a transformer?
107. What is difference between 1 phase transformer and 3 phase transformer?
108. What types of capacitors are used in a ceiling fan?
109. What is a booster in power system?
110. What are the different types of faults which occur in a power system?
111. Why is series generator not generally used?
112. What does the name plate of DC generator generally indicates?
113. What is Buchholz relay? Which equipment is protected by it?
114. Define the term sensitivity and selectivity of a relay?
115. What are the effect of temperature all Sag in an overhead line?
116. What are the effects of Corona in transmission line?
117. What is the difference between heating wire and fuse wire?
118. How to get a high DC voltage for testing purposes?
119. How to increase or decrease the range of a voltmeter?
120. What is the resistance of an ideal ammeter?

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