INTERVIEW QUESTIONS: -
1.
Question 1
The power system industry is concerned with the generation, transmission, and distribution of
electrical energy.
1 / 1 point
TRUE
FALSE
Correct
Power system deals with the business of generation, transmission, and distribution of electrical
energy.
2.
Question 2
Generation, transmission, and distribution of electrical power are all part of a traditional electric
power system.
1 / 1 point
TRUE
FALSE
Correct
traditional electric power systems have three separate components: generation, transmission,
and distribution.
3.
Question 3
The purpose of an electric power system is to link the power plant to the load of the consumers.
1 / 1 point
TRUE
FALSE
Correct
The function of an electrical power system is to connect the power station to the consumers'
load.
4.
Question 4
______________ is the process of converting energy found in various forms across nature into
electrical energy.
1 / 1 point
Electric power generation
Mechanical Power Generation
Electrical and Mechanical Power Generation
none of these
Correct
The conversion of energy available in different forms in nature into electrical energy is known as
power generation of electrical energy.
5.
Question 5
_______________ uses steam generated by the combustion of oil, liquid natural gas (LNG),
coal, and other materials to turn generators and generate electricity.
1 / 1 point
Thermal power generation
Wind power Generation
Synchronous generator
Asynchronous Generator
Correct
When oil and coal are burnt in boilers, thermal energy is released. This thermal energy is used to
make steams to run steam turbines. Similarly, natural gas is burned in gas turbine to produce
electrical energy.
6.
Question 6
Pressure is generated in the working fluid cycle in thermal power plants by ________
1 / 1 point
condenser
superheater
feedwater pump
turbine
Correct
The heated flue gases from burner converts water in water tubes into steam.
7.
Question 7
_____ is the bulk transfer of electrical energy from a generating facility, such as a power station
or power plant, to an electrical substation, where voltage is altered and delivered to consumers
or other substations.
1 / 1 point
Electrical power transmission
distribution system
Electrical Power Generation
none of these
Correct
The transmission system is made up of transmission lines that transports power from the
generation system through power transformers
8.
Question 8
The traditional electric power business was run as a vertically integrated regulated monopoly,
with generating, transmission, and distribution facilities all owned by the same company.
1 / 1 point
TRUE
FALSE
Correct
The main objective of electric power restructuring is to significantly reduce the cost of power
charge to small businesses and consumers.
9.
Question 9
The major goal of electric power restructuring is to raise the cost of electricity charged to small
enterprises and consumers dramatically.
1 / 1 point
TRUE
FALSE
Correct
Generation utilities will no longer have a monopoly, small businesses will be free to sign contract
for buying power from cheaper sources.
10.
Question 10
The primary objective of all power system is
1 / 1 point
to provide Reliable power
to provide Quality power
to Increase Cost of power
to provide Reliable and Quality Power
Correct
to maintain continuity of quality power supply to customers Whenever abnormal electrical fault
conditions occur the protective equipment should function so as to reduce damage and minimize
outage time to customers
11.
Question 11
______ is the abnormal condition of the electrical system which damages the electrical
equipment and disturbs the normal flow of the electric current
1 / 1 point
Electrical fault
mechanical fault
Both 1 and 2
none of these
Correct
An electrical fault is an abnormal condition caused by equipment failures such as transformers
and rotating machines, human errors, and environmental conditions.
12.
Question 12
The following are examples of transmission line faults that could occur:
1. 3-phase fault
2. L-L-G fault
3. L-L fault
4. L-G fault
The increasing order of severity of the fault from the stability point of view is
1 / 1 point
4-3-2-1
2-3-4-1
1-3-2-4
3-1-4-2
Correct
Among the faults, 3-phase faults is most severe and line to ground is least severe.
LG<LL<LLG<LLL
13.
Question 13
That fault on the power system which gives rise to equal fault currents in the lines with
120degree displacement is called a
1 / 1 point
unsymmetrical fault
open conductor fault
symmetrical fault
none of these
Correct
symmetrical or balance fault, during a short circuit gives the equal currents in all the phases.
14.
Question 14
If all of the sequence voltages at a power system's fault location are equal, the fault is a
1 / 1 point
Three-phase fault
Line to ground fault
Line to line fault
Double line to ground fault
Correct
In this fault, two lines come in contact with each other along with ground. Hence Va0=Va1=Va2
15.
Question 15
The power system is subjected to a fault which makes the zero-sequence component of current
equal to zero. The nature of fault is
1 / 1 point
Line to ground fault
Double line fault
Double Line to ground fault
Three phase to ground fault
Correct
In this fault, there is no ground. Hence the zero sequence current is zero
16.
Question 16
___________ is a series type unbalanced fault that occurs in a power system.
1 / 1 point
Line to line fault
Double line to ground fault
single line to ground fault
open circuit fault
Correct
open circuit fault also known as series faults, which are unsymmetrical or unbalanced types of
faults except three phase open fault. These faults occur due to the failure of one or more
conductors
17.
Question 17
A ____ is a logical element which process the inputs (mostly voltages and currents) from the
system and issues a trip decision if the pickup level of actuating signal is reached.
1 / 1 point
Switch
Fuse
Protective relay
Isolator
Correct
A relay is designed to trip circuit breaker when a fault is detected.
18.
Question 18
An ability of Relay system to operate under predetermined condition is
0 / 1 point
Sensitivity
Selectivity
Stability
Reliability
Incorrect
Refer Desirable Features of Protective Relaying systems to know about desirable features of
protective relay systems.
19.
Question 19
A distance relay measure
1 / 1 point
difference in voltage
difference in current
difference in impedance
difference in phase
Correct
the relay operates depending upon the impedance between the point of fault and the point where
relay is installed.
20.
Question 20
The ____ faults are due to short circuits in conductors
1 / 1 point
series
shunt
open
fixed
Correct
Shunt faults involves a short circuit between conductor and ground (or) two or more conductors.
1
Current Transformer is an 'instrumentation' transformer which convert ____ values of currents to
_____ values
1 / 1 point
low, low
low, high
high, high
high, low
Correct
The objective of CT is to step down higher values of current to lower value.
2.
Question 2
Instrument transformers does not electrically isolate the relaying system from the equipment
1 / 1 point
TRUE
FALSE
Correct
Instrument transformers electrically isolates the relaying system from the equipment.
3.
Question 3
A magnetic core of CT made up of silicon steel laminations links both the windings for providing
0 / 1 point
a low reluctance path
a high reluctance path
a low resistance path
a high resistance path
Incorrect
Refer Basics of Current Transformers (CT) to know about constructional details of CT
4.
Question 4
When a current transformer's secondary winding is opened while the primary winding is carrying
current, the following happens:
1 / 1 point
Transformer will burn immediately
High induced EMF is produced in the secondary winding
Flux density in the core gets weakened
High current is produced in the secondary winding
Correct
There is no counter mmf in the secondary winding if the secondary is opened. The entire primary
current operates as a magnetizing current, causing high secondary voltages. This results in high
core losses and heat, which in turn causing CT to be burned.
5.
Question 5
Voltage transformers are designed to have _____________
1 / 1 point
high leakage reactance
high magnetizing current
high magnetizing reactance
low magnetizing reactance
Correct
Voltage transformers are designed with low leakage reactance, low loss and high magnetizing
reactance.
6.
Question 6
_____________ is the value of the CT's secondary voltage over which the output current no
longer follows the input current linearly within the claimed accuracy limitations.
1 / 1 point
Cut-in voltage
breakdown voltage
flashover voltage
knee-point voltage
Correct
The saturation last until the principal transient current falls below the saturation level.
7.
Question 7
Saturation in the current transformer core is caused by the presence of _____ in fault current.
1 / 1 point
primary current
DC offset
secondary current
magnetizing current
Correct
DC offset in fault current is the causes of saturation in current transformer core.
8.
Question 8
The acronym OTDR stands for
1 / 1 point
Optical Time Data Register
Optical Transfer Data Rate
Optical Time Domain Reflectometer
Optimal Transfer Domain Rate
Correct
It is an optoelectronic instrument used to characterize an optical fiber.
9.
Question 9
The VT circle diagram is a quick and easy way to determine accuracy at any load and power
factor
1 / 1 point
TRUE
FALSE
Correct
A simple technique to assess accuracy at any load and power factor is to use the PT or VT circle
diagram.
10.
Question 10
The maximum load in VA that the transformer can carry at the rated secondary voltage without
exceeding the temperature rise is known as
1 / 1 point
PT thermal rating
mismatch of CT
saturation
difference in connection of CT
Correct
IEEE standards identify five rating parameters for voltage transformers, basic impulse insulation
level in terms of full-wave test voltage, rated primary voltage and ratio, rated frequency, accuracy
ratings, thermal burden rating.
1.
Question 1
In the first few cycles, any motor, such as an induction or synchronous motor, must be
considered as a source for computing fault current.
1 / 1 point
TRUE
FALSE
Correct
Due to moment of inertia the motor will contribute to the fault current.
2.
Question 2
The Electrical Fault Occurrence Statistics Descending order
A. Single-phase-to-ground
B. Phase-to-phase-to-ground
C. Phase-to-phase
D. Three-phase
1 / 1 point
A,B,C,D
B,A,D,C
B,A,C,D
A,B,D,C
Correct
the electrical fault occurrence for LG-(70-80)% LLG-(10-17)% LL-( 8-10)% , LLL-( 2-3)% percent.
3.
Question 3
If an IDMT relay has a plug setting of 50% and a CT ratio of 400/5, and the fault current is 3000
A, the plug setting multiplier is,
1 / 1 point
7.5
15
17.5
37.5
Correct
The plug setting multiplier is the ratio of fault current to the product of plug setting and CT ratio
Plug setting= 0.5*5=2.5A
CT Ratio=400/5=80
PSM=3000/(2.5*80)=15
4.
Question 4
Calculate the relay's operating current for a 5 A load, a 2.2-second IDMT rating, and a 125
percent relay setting.
1 / 1 point
2.5
5
12.5
6.25
Correct
The operating current of relay is calculated as the product of rated current in CT and current
setting= 1.25*5=6.25A
5.
Question 5
An earth fault relay has a setting of 150 percent and a current rating of 5 amps. It's connected to
a 200:5 ratio current transformer. The primary current detected by the relay is
1 / 1 point
7.5 A
20 A
300 A
1500 A
Correct
The primary of the CT is given by product of CT turns ratio and pick up current = (1.5*5*(200/5))=
300A
6.
Question 6
In a earth fault relay ______ helps in the detection of a fault.
1 / 1 point
positive sequence current
zero sequence current
negative sequence current
positive sequence voltage
Correct
earth fault relays employ zero sequence current, internal phase present for, fault detection to
offer sensitive protection.
7.
Question 7
The time between the initiation of the fault and the moment when the fuse is blown off is known
as________ time in fuses.
0 / 1 point
Pre-arching time
Arching time
Post-arching time
Operating time
Incorrect
Refer Fuses and Miniature Circuit Breaker for protection to know about basics of operation of
fuses.
8.
Question 8
________ are rewireable fuses that interrupt low current faults.
1 / 1 point
Kit-kat fuses
Knife blade type fuse
bolted type fuse
switch type fuse
Correct
The rewire fuse also called as kit-kat type is used for interruption of low value of fault current.
9.
Question 9
Which among the following is not a type of inverse definite minimum time (IDMT) relays
1 / 1 point
Standard Inverse
Very Inverse
Extremely inverse
Most Inverse
Correct
classified as, standard inverse, very inverse, and extremely inverse relays.
10.
Question 10
ANSI Device Number for Time-overcurrent relay is
1 / 1 point
52
51
50
53
Correct
According to IEEE C37.2 device number 51 represents time over current relay
1.
Question 1
In a grounded system with low grounding resistance, the ground fault current will be
1 / 1 point
large
small
very small
negligibly small
Correct
If the grounding resistance is low, the ground fault current will be large, and the system will
resemble the effectively solidly grounded system.
2.
Question 2
The current transformer protects the star-star power transformer by having
1 / 1 point
Star/star connections
Delta/delta connections
Star/delta connections
Delta/star connections
Correct
In order to nullify the phase shift of the Power transformer (PT), The Current transformers (CT)
connected in a reverse configuration. The star-star power transformer is protected by the current
transformer having delta/delta connections.
3.
Question 3
To protect against stator insulation failure, what form of protection is offered on a generator?
1 / 1 point
Differential protection
Overcurrent relay
Thermocouple actuated alarm
Reverse power relay
Correct
Generally, differential relays are used to protect the equipment against internal faults. Merz price
protection scheme is one form of the differential relay which is used to protect the stator winding
of Alternator from the internal faults.
4.
Question 4
For power transformers to have differential protection (delta-delta), the current transformers will
need to have
1 / 1 point
Delta-delta connection
Star-delta connection
Star-star connection
Delta-star connection
Correct
In order to nullify the phase shift of the Power transformer (PT), The Current transformers (CT)
connected in a reverse configuration. The delta-delta power transformer is protected by the
current transformer having star-star connections.
5.
Question 5
Merz price differential relay is used to protect transformers against
1 / 1 point
internal shorts circuits and ground faults
oil failure
core failure
transmission line fault
Correct
Merz-Price differential protection is used to safeguard the transformer against internal short
circuits, internal ground faults, and interturn shorts.
6.
Question 6
For electrical equipment protection, differential relays are employed to detect
1 / 1 point
internal faults
overcurrent
reverse current
reverse power
Correct
Generally, differential relays are used to protect the equipment against internal faults. Merz price
protection scheme is one form of the differential relay which is used to protect the stator winding
of Alternator from the internal faults.
7.
Question 7
To protect transmission lines utilizing the Translay protection system, the following number of
pilot wires is required:
1 / 1 point
1
2
3
4
Correct
The translay relay is another type of differential relay. The arrangement is similar to overcurrent
relay but the secondary winding is not closed on itself. The number of pilot wires required to
protect transmission lines using translay protection system is two.
8.
Question 8
Which of these is a type of unit protection in a feeder?
0 / 1 point
Directional time graded protection
Distance protection
Balanced voltage system
Unbalanced voltage system
Incorrect
Refer Merz Price Differential Relay to know about unit protection
9.
Question 9
The relay used to protect the feeder is
1 / 1 point
Undervoltage relay
Translay relay
Thermal relay
Buchholz relay
Correct
The translay relay is a differential relay. The arrangement is similar to overcurrent relay, but the
secondary winding is not closed on itself. These types of relays are used in the feeder protection
10.
Question 10
Connecting the neutral to the ground through a reactor is called
1 / 1 point
resistance grounding
capacitive grounding
short grounding
reactance grounding
Correct
In a reactance grounding, reactance is connected between neutral and ground to limit the fault
current. reactance grounding. The selection of the reactance is important for effective grounding.
1.
Question 1
The condition for maximum torque angle is obtained when the current is __________ ahead of
the polarizing voltage.
0 / 1 point
30 degrees
90 degrees
45 degrees
60 degrees
Incorrect
Refer Earth Fault Protection of AC Motors to know about voltage polarizing source.
2.
Question 2
An induction motor is the same as
1 / 1 point
D.C. compound motor
D.C. series motor
Asynchronous motor
Correct
An induction motor is called asynchronous motor because the actual speed of the motor is not
equal to the synchronous speed of the motor. The synchronous speed of the motor is always
more than the actual speed of the motor.
3.
Question 3
The semiconductor device used in ac motor soft starter to control voltage is
0 / 1 point
MOSFET
IGBT
Thyristor
TRIAC
Incorrect
Refer Start / Stall Protection of AC Motors to know about soft starter.
4.
Question 4
Slip is 4% for a three-phase 440 V, 50 Hz induction motor. The rotor current frequency will be
1 / 1 point
2 Hz
5Hz
25Hz
50Hz
Correct
In an induction motor, the rotor current frequency relate to slip is given by fr=s*f. Therefore
fr=0.04*50=2Hz
5.
Question 5
_______ is used to protect the induction motor from running in the reverse direction.
1 / 1 point
Over voltage protection
over current protection
phase reversal protection
under voltage protection
Correct
Phase reversal protection is used to protect the induction motor, from running in reverse
direction. Normally running a motor in reverse direction does not affect the system when the
motor is empty. But Running a induction motor in reverse direction with mechanical loads causes
heavy load current flow on the motor’s stator winding
6.
Question 6
____ is the minimal torque produced by an electric motor from zero to maximum load speed.
1 / 1 point
Break down Torque
Pull-up Torque
Pull out Torque
Locked Rotor Torque
Correct
The Pull-up Torque is the minimum torque developed by an electrical motor when it runs from
zero to full-load speed
7.
Question 7
______ is employed to protect the motor against Stalling
1 / 1 point
Instantaneous over-current relay
Thermal overload relay
Buchholz relay
mho relay
Correct
Stalling protection can also be provided by a separate definite time overcurrent relay which is
operated only after a certain predefined time if overcurrent persists beyond that period.
8.
Question 8
_____ are provided for the protection of motor against single phasing.
1 / 1 point
Instantaneous over-current relay
Thermal overload relay
Buchholz relay
mho relay
Correct
It provides the most accurate tripping of the motor during overload & single phasing.
9.
Question 9
When the motor is supplied with an imbalanced supply voltage, _________flow into the motor
1 / 1 point
Positive sequence currents
Zero Sequence currents
Negative sequence currents
only positive and zero sequence currents flows
Correct
During the unbalanced conditions, negative sequence currents. These currents are undesirable
which will generate high and possibly dangerous temperatures in a very short time.
10.
Question 10
Which of the following relays is utilized for overload protection of motors?
1 / 1 point
Buchholz relay
Thermal relay
Impedance relay
mho relay
Correct
A thermal relay in which when a bimetallic strip is heated up by a heating coil carry over current.
It is generally used where overload is allowed to flow for predetermined amount of time before it
trips. An application of thermal relay is overload protection of electric motor