1. Protection and switchgear
Prepared by
R.Karthi kn

2. 1. Identify the inductive element a)Transistor b)Transformer c)diode d)none of these

3. 2. Identify the protective device
a)CB
b)Relay
c)both A & B
d)none of these

4. 3. Identify the element that subjected to more faults
a )motor
b) busbar
c)diode
d) Transformer

5. 4. In protective apparatus CT is connected to a)CB b)Relay c)PT d)none of these

6. 5. In protective apparatus trip coil in overcurrent relay is connected to
a)CB
b)Relay
c)PT
d)CT

7. 6. In induction disc type which currents will be formed
a) forward current
b) Reverse current
c) eddy current
d) Saturation current

8. 7. Other name of induction disc type relay is
a) shaded pole relay
d) Permanent magnet relay
c) mho relay
d)none of these

9. 8. Other name of admittance relay is
a) shaded pole relay
d) Permanent magnet relay
c) mho relay
d)Watt hour meter relay

10. 9. In induction cup type relay will be formed
a) high torque
b) high current
c) low torque
d)low current

11. 10.In relay is mandatory
a)High impedance
b)low impedance
c)zero impedance
d)very high impedance

12. 11. Relay contacts are normally made up of: a) Silver contacts b) Copper contacts c) Aluminium contacts d) Lead contacts

13. 12. Sparking between the contacts can be reduced by inserting: a) A capacitor in parallel with the contacts b) A capacitor in series with the contacts c) A resistor in the line d) A reactor in the line

14. 13. The contact resistance is least affected by: a) Shape of the contact faces b) Ambient temperature c) Mechanical forces applied d) Amount of surface commutation

15. 14.  The arc voltage produced in an ac circuit breaker is always: a) In phase with the arc current b) Lagging the arc current by 90 deg c) Leading the arc current by 90 deg d) In phase opposition with the arc current

16. 15. Breaking capacity of the circuit breaker is usually expressed in: a) MVA b) MW c) Kilo-amperes d) kV

17. 16. Which of the following circuit breakers produce least arc energy: a) Plain oil b) Minimum oil c) Air blast d) Air break

18. 17.  A thermal protection switch is used to provide protection against: a) Over load b) Temperature c) Short circuit d) Over voltage

19. 18. In a circuit breaker the current which exists at the instant of contact separation is known as
(A) re striking current
(B) surge current
(C) breaking current
(D) recovery current.

20. 19. Sulphur hexafluoride is a
(A) Conductor of electricity
(B) Semi-conductor
(C) Inactive gas
(D) Dielectric.

21. 20. As the force on contact is increased, the contact resistance will
(A) increase linearly
(B) increase exponentially
(C) remain unaltered
(D) decrease.

22. 21. The arcing contacts in a circuit breaker are made of
a)copper tungsten alloy
b)Silver alloy
c)lead
d)aluminium

23. 22.On which of the following routine test conducted
a)relay
b)CB
c)fuse
d)CT

24. 23. In overcurrent relay , plug setting ranges from 50 % to
a)150
b)200
c)300
d)500

25. 24. In overcurrent relay , plug setting range is determined by
a)15 steps
b)35 steps
c)25 steps
d)none of these

26. 25.The main function of a fuse is to
(a) protect the line
(b) open the circuit
(c) protect the appliance
(d) prevent excessive current

27. 26.The upper magnet in induction type overcurrent relay is shaped a)T b)U c)E d)none of these

28. 27.EIDMT means
a) Extra inverse current definite minimum time
b) Enormous inverse current definite minimum time
c) Extremely inverse current definite minimum time
d) Efficient inverse current definite minimum time

29. 28 Overload relays are of…… type
28 Overload relays are of…… type. (a) induction (b) solid state (c) thermal (d) electromagnetic (e) all above

30. 29. Magnetic circuit breaker has ______ trip action
29. Magnetic circuit breaker has ______ trip action. (a) delayed (b) instantaneous (c) both of the above (d) none of the above

31. 30.  In order that current should flow without causing excessive heating or voltage drop, the relay contacts should (a) have low contact resistance (b) be clean and smooth (c) be of sufficient size and proper shape (d) have all above properties

32. 31. Circuit breakers usually operate under (a) transient state of short-circuit current (b) sub-transient state of short-circuit current (c) steady state of short-circuit current (d) after D.C. component has ceased

33. 32.  Directional relays are based on flow of (a) power (b) current (c) voltage wave (d) all of the above

34. 33. A differential relay measures the vector difference between (a) two currents (b) two voltages (c) two or more similar electrical quantities (d) none of the above

35. 34. When a transmission line is energized, the wave that propagates on it is (a) current wave only (b) voltage wave only (c) both (a) and (b) (d) power factor wave only

36. 35. The voltage appearing across the contacts after opening of the circuit breaker is called______voltage. (a) recovery (b) surge (c) operating (d) arc (e) none of the above

37. 36. Ionization in circuit breaker is facilitated by (a) high temperature (b) increase of mean free path (c) increasing field strength (d) all of the above

38. 37. In a circuit breaker the basic problem is to (a) maintain the arc (b) extinguish the arc (c) transmit large power (d) emit the ionizing electrons

39. 38. Shunt capacitance is neglected while considering (a) short transmission line (b) medium transmission line (c) long transmission line (d) medium and long transmission lines

40. 39. The interaction between a transmission line and communication line is minimized by (a) transposing transmission as well as communication lines (b) increasing the height of the trans-mission line tower (c) increasing the distance between the two lines (d) all of the above

41. 40. Which of the following statements is incorrect
40. Which of the following statements is incorrect ? (a) Lightning arrestors are used before the switchgear (b) Shunt reactors are used as compensation reactors (c) The peak short current is (1.8 xV2) times the A.C. component (d) The MVA at fault is equal to base MVA divided by per unit equivalent fault reactance