Switchgear and Protection Mcq with Answers

41. The use of high speed circuit breakers

(a) improves transient stability.
(b) decreases transient stability.
(c) has no effect on system stability.

42. The use of fast acting relays and circuit breakers for clearing a sudden short-circuit on a transmission line between a generator and the receiving end bus improves the transient stability of the machine because the

(a) short-circuit current becomes zero.
(b) post-fault transfer impedance attains a value higher than that during the fault.
(c) ordinate of the post-fault power-angle characteristic is higher than that of during fault characteristic.
(d) voltage behind the transient reactance increases to a high.

43. Load flow study is carried out for

(a) load-frequency control.
(b) planning of power system.
(c) fault calculations.
(d) study of stability of the system.

44. Load flow studies must be made on a power system before

(a) making short-circuit studies but not for transient stability studies on the power system.
(b) making transient stability studies but not for short-circuit studies on the power system.
(c) making both short-circuit and transient stability studies on the power system.
(d) for neither making short-circuit studies nor transient stability studies on the power system.

45. Load flow studies involve solving simultaneous

(a) linear algebraic equations.
(b) non-linear algebraic equations.
(c) linear differential equations.
(d) nonlinear differential equations.

46. In a power system, each bus or node is associated with four quantities, namely

1. real power. 2. reactive power. 3. bus-voltage magnitude. 4. phase angle of the bus voltage.

For load-flow solution, among these four, the number of quantities to be specified is
(a) any one.
(b) any two.
(c) any three.
(d) all the four.

47. Consider the following quantities :

1. Real power 2. Reactive power 3. Power factor 4. Input current 5. Bus voltage magnitude 6. Bus voltage phase-angle.

For the purpose of the load flow studies of a power system, each bus or node is associated with which one of the combinations of the above four quantities ?
(a) 1, 3, 4 and 5
(b) 1, 2, 3 and 4
(c) 2, 3, 5 and 6
(d) 1, 2, 5 and 6

48. In load flow studies of a power system, a voltage control bus is specified by :

(a) Real power and reactive power.
(b) Reactive power and voltage magnitude.
(c) Voltage and voltage phase angle.
(d) Real power and voltage magnitude.

49. For a load-flow solution the quantities normally specified at a voltage controlled bus are

(a) P and Q
(b) P and |V|
(c) Q and |V|
(d) P and δ.

50. Load bus is specified by

(a) P and V.
(b) P and δ.
(c) P and |V|.
(d) P and Q.

51. At slacks bus, which one of the following combinations of variables is specified ?

(a) |V|, δ
(b) P, Q
(c) P, |V|
(d) Q, |V| (The symbols have their usual meaning)

52. In a power system, the maximum number of buses are

(a) generator buses.
(b) load buses.
(c) slack buses.
(d) P-V buses.

53. If a voltage controlled bus is treated as a load bus, then which one of the following limits would be violated ?

(a) Voltage.
(b) Active power.
(c) Reactive power.
(d) Phase angle.

55. In load-flow analysis, the load connected at a bus is represented as

(a) constant current drawn from the bus.
(b) constant impedance connected at the bus.
(c) voltage and frequency dependent source at the bus.
(d) constant real and reactive power drawn from the bus.

56. The voltage of a particular bus can be controlled by controlling the

(a) active power of the bus.
(b) reactive power of the bus.
(c) phase angle. (d) both
(a) and (b).
(e) (b) and (c).

57. The voltage of a particular bus can be controlled by controlling

(a) phase angle.
(b) reactive power of the bus.
(c) active power of the bus.
(d) phase angle and reactive power.

58. A power system consists of two areas connected via a tie line. While entering the data for load flow the tie line parameters and its connectivity data were inadvertently left out. If the load flow program is run with this incomplete data, then the load flow calculations will converge only if

(a) One slack bus is specified in the first area.
(b) One slack bus is specified in the second area.
(c) One slack bus is specified in either of the two areas.
(d) Two slack buses, one in each area, are specified.

• Switchgear and Protection MCQ Part – 1
• Switchgear and Protection MCQ Part – 2
• Switchgear and Protection MCQ Part – 3
• Switchgear and Protection MCQ Part – 4

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