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
Comments
as the steady state stability limit is directly proportional to the excitation voltage and does not depend upon the moment of inertia of rotor