Multiple Choice Questions on Power Systems - 5

Important multiple choice questions on power systems

1.       Which one of the following statements is true?
A)     Steady state stability limit is greater than transient state stability limit
B)      Steady state stability limit is equal to transient state stability limit
C)      Steady state stability limit is less than the transient stability limit
D)     No generalisation can be made regarding the equality of otherwise of the steady state stability limit and transient stability limit
2.       If the integral control of a single area system, when  the system frequency error is reduced to zero
A)     The integrator output and the speed changer position attains a constant value
B)      The integrator output increases but the speed changer position also comes down
C)      The integrator output decreases and the speed changer position also comes down
D)     The integrator output decreases but the speed changer position moves up
3.       The steady-state stability limit of a synchronous generator can be increased by
A)     An increase in its reactance
B)      An increase in the excitation of the machine
C)      A decrease in the moment of inertia of the machine
D)     An increase in the moment of inertia of the machine
4.       Steady-state stability of power system is the ability of the power system to
A)     Maintain voltage at the rated voltage level
B)      Maintain frequency at exactly 50 Hz
C)      Maintain a spinning reserve margin at all times
D)     Maintain synchronism between machines and external tie lines
5.       The transient state stability of the power system can be effectively improved by
A)     Excitation control
B)      Phase shifting transformer
C)      Single pole switching of circuit breakers
D)     Increasing the turbine valve opening
6.       Rated breaking capacity (MVA) of a circuit breaker is equal to
A)     The product of rated breaking current (kA) and rated voltage (kV)
B)      The product of rated symmetrical breaking current (kA) and rated voltage (kV)
C)      The product of rated breaking current (kA) and fault voltage (kV)
D)     Twice the value of rated current (kA) and rated voltage (kV0
7.       To prevent maloperation of differentially connected relay while energising a transformer, the relay restraining coil is biased with
A)     Second harmonic current
B)      Third harmonic current
C)      Fifth harmonic current
D)     Seventh harmonic current
8.       Lighting arresters are used in power systems to protect electrical equipments against
A)     Direct strokes of lightning
B)      Power frequency of over voltages
C)      Over voltages due to lightning stroke
D)     Over currents due to lightning stroke
9.       While using air-blast circuit breaker current chopping phenomenon is often observed when
A)     A long over head line is switched off
B)      A bank of capacitors is switched off
C)      A transformer on no-load is switched off
D)     A heavy load is switched off
10.   A lightning arrestor connected the line and earth in a power system
A)     Protects the terminal equipment against travelling surges
B)      Protects the transmission lines against direct lightning stroke
C)       Suppresses high frequency oscillations in the line

D)     Reflects back the travelling wave approaching it



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universe boss said…
i think the question 4 answer is B. you may wanna correct that
universe boss said…
not question 4 but question 3 answer is B
as the steady state stability limit is directly proportional to the excitation voltage and does not depend upon the moment of inertia of rotor

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