electrical

Switchgear and Protection MCQ Objective Questions and Answers Page - 8

1.
 The method of neutral grounding affects the A Positive-sequence network B Negative- sequence network C Zero- sequence network D Both Positive- and Zero-sequence network Answer : C Explanation :
2.
 The earth transformer is used to A Avoid the harmonics in the transformers B Provide artificial neutral earthing where neutral point is not accessible C Improve stability of the system D Measure the voltage Answer : B Explanation :
3.
 In an isolated neutral system, when a single line to ground fault occurs A Persistent arcing grounds will be developed B Voltage in the healthy phases rise to full line value causing insulation breakdown C The capacitive current in the faulty phase rises to  3 times its normal value D All of the above Answer : D Explanation :
4.
 The voltage of a particular bus is regulated by controlling the A Active power of the bus B Reactive power of the bus C Phase angle D Phase angle and reactive power Answer : B Explanation :
5.
 In ac distribution system the voltage can be controlled by using A Tap changing transformer B Booster transformer C Induction regulator D Any of the above Answer : D Explanation :
6.
 The changing transformers are employed for A Stepping down the voltage B Stepping up the voltage C Supplying low voltage current to instruments D Both Stepping up and Stepping down the voltage Answer : D Explanation :
7.
 The best location for use of a booster transformer in a transmission line is A At the sending end B At the receiving end C At the intermediate point D Anywhere in the line Answer : C Explanation :
8.
 For voltage control in ac distribution system the induction regulators have the advantage(s) of A Reliability of operation B Operation independent of load and power factor variations C Stepless voltage variations without arcing or short-circuiting of turns as in the case of transformers D All of the above Answer : D Explanation :
9.
 Series capacitor is used in a transmission line to A Compensate the voltage drop B Reduce line losses C Limit short-circuit current D Improve load power factor Answer : A Explanation :
10.
 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 : B Explanation :
11.
 _____________  are used provide compensation at the receiving end of a transmission line so as to improve its voltage profile. A Condensers B Resistors C Reactors D Condensers, resistors or reactors Answer : A Explanation :
12.
 What will happen if a short-circuit fault occurs in a switched capacitor controlled reactor  ? A Oscillation B Capacitor discharge C Over voltage D Noise Answer : A Explanation :
13.
 An AC capacitor is to be switched in parallel with  AC  line using back to back connected thyristor. What is the firing angle of thyristor for first switching ? A 00 B 1800 C 900 D 450 Answer : C Explanation :
14.
 In between the generating station (power house) and consumers a number of transformation and switching stations exist, these are called the A Switchgears B Substations C Intermediate substations D Transformation stations Answer : B Explanation :
15.
 Which of the following is provided with arcing horns  ? A Isolator B Air-break switch C Oil switch D None of the above Answer : B Explanation :
16.
 Pole mounted substations are used in A Primary transmission system B Secondary transmission system C Primary distribution system D Secondary distribution system Answer : D Explanation :
17.
 With large reactance interconnector between two power stations A The power stations may fall out of step due to large angular displacement between the power stations. B Power will be transferred with minimum power losses. C Power will be transferred with voltage fluctuation and noise. D None of the above. Answer : A Explanation :
18.
 AC network analyser is employed for solving the problem of A Load flow B Load flow and stability C Load flow and short circuit D Load flow, stability and short circuit Answer : D Explanation :
19.
 Power system stability is defined as A That attribute of the system or part of the system which enables it to develop restoring forces between the elements there of equal or greater than disturbing forces so as to restore a state of equilibrium between the elements. B The maximum power flow possible through some particular point in the system when the entire or part of the system is disturbed. C Both (a) and (b) D Neither (a) nor (b) Answer : A Explanation :
20.
 Steady-state stability of a power system is the ability of the power system to A Maintain voltage at the rated voltage level B Maintain frequency exactly at  50 Hz C Maintain a spinning reserve margin at all times D Maintain synchronism between machines and on external tie lines Answer : D Explanation :
21.
 Transient disturbances are caused by A Sudden load changes B Switching operations C Inadvertent tripping of lines and generators D All of the above Answer : D Explanation :
22.
 Transient stability of a  3-phase  power systems having more than one synchronous generator is not affected by which one of the following specifications  ? A Initial operating conditions of generators B Quantum of large power disturbance C Quantum of large power disturbance D Small changes in system frequency Answer : D Explanation :
23.
 The power transmission capacity of a transmission line is A Proportional to transmission voltage B Proportional to the square of transmission voltage C Inversely Proportional to transmission voltage D Inversely Proportional to the square of transmission voltage Answer : B Explanation :
24.
 The load carrying capability of a long ac transmission line is A Always limited by the conductor size B Limited by stability considerations C Reduced at low ambient temperatures D Decreased by the use of bundled conductors of single conductors Answer : B Explanation :
25.
 Maximum power will be transferred from the sending end to the receiving end by a transmission line when A The line reactance is  $\sqrt{3}$  times its resistance, i.e., X = $\sqrt{3}$  R B The torque angle $\delta&space;=&space;90^{0}$ C Both (a) and (b) D Neither (a) nor (b) Answer : C Explanation :
26.
 The stability of the power system is not affected by A Generator reactance B Line reactance C Line losses D Excitation of generators Answer : C Explanation :
27.
 The power systems are operated with power angle around A $10^{0}$ B $30^{0}$ C $70^{0}$ D $80^{0}$ Answer : B Explanation :
28.
 Which of the following statements is true  ? A Steady-state stability limit is greater than transient stability limit. B Steady-state stability limit is  equal to transient stability limit. C Steady-state stability limit is less than the transient stability limit. D No generalisation can be made regarding the equality or otherwise of the steady, state stability limit and transient stability limit. Answer : A Explanation :
29.
 The methods employed in improving the system stability are A Increasing the system voltage only B Reducing the transfer reactance only C Using high-speed auto-reclosing circuit breaker only D Using all (a), (b), (c) together Answer : D Explanation :
30.
 Series capacitors are used to A Compensate for line inductive reactance and improve the stability of the power system. B Improve the voltage. C Reduce fault level. D Improve the power factor. Answer : A Explanation :
31.
 A 2-pole, 50 Hz, 11 kV, 100 MW alternator has a moment of inertia of  10,000 kg.m2. the value of inertia constant,  H is A 3.9 s B 4.3 s C 4.6 s D 4.9 s Answer : D Explanation :
32.
 In a multimachine interconnected system, subsequent to a  3-phase  fault, the transient stability is examined by A Equal-area criterion B Solution of swing equations C Either by Equal-area criterion  or  by Solution of swing equations D Combination of Equal-area criterion   and  Solution of swing equations Answer : B Explanation :
33.
 Equal-area criterion is employed to determine  : A The steady-state stability B The transient stability C The reactive power limit D The rating of a circuit breaker Answer : B Explanation :
34.
 Equal area criteria in power systems is used in the context of A Deciding maximum loading for a given excitation. B Stability of a machine connected to infinite bus bar. C Stability of power systems in which many machines are connected to infinite bus bar. D Load distribution between a single machine and load drawn from infinite bus bar. Answer : B Explanation :
35.
 For what value of damping parameter, the transient stability is assured by equal area criterion  ? A Independent of systems damping B Of only damping is exactly zero C For all values of damping parameters D If only damping is positive and finite Answer : B Explanation :
36.
 Critical clearing angle is related to A Stability study of power system B Power flow study of power system C Regulation of transmission line D Power factor improvement of the system Answer : A Explanation :
37.
 For a fault in a power system, the term clearing time is related to A Reactive power limit B Transient stability limit C Short-circuit current limit D Steady-state stability limit Answer : B Explanation :
38.
 For which one of the following types of motors, is the equal-area criterion for stability applicable  ? A 3-phase synchronous motor B 3-phase induction motor C DC series motor D DC compound motor Answer : A Explanation :
39.
 The transient stability limit of a power system can be appreciably increased by introducing A Series inductance B Shunt inductance C Series capacitance D Shunt capacitance Answer : C Explanation :
40.
 The initial accelerating power  (in pu)  will be A 1.0 B 0.6 C 0.56 D 0.4 Answer : C Explanation :