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WorksheetsPSPU QUIZ
Total questions: 107
Worksheet time: 54mins
In case of overload, transformer protection usually depends on:
Differential relay
Buchholz relay
Thermal relay
Distance relay
Current transformers (CTs) are used primarily for:
Voltage measurement
Current measurement and protection
Power factor correction
Improving transmission efficiency
Which device is commonly used to protect power system equipment from lightning surges?
Current Transformer
Circuit Breaker
Isolator
Lightning Arrester
A 220 kV substation uses lightning arresters. Their location should be:
Near the generator
Near the transformer terminals
At load end only
At mid-point of transmission line
If a relay fails to operate, which system feature ensures backup protection?
Primary protection
Fuse protection
Secondary protection
Backup protection
Which type of stroke occurs when lightning directly hits the conductor?
Indirect stroke
Shielding stroke
Direct stroke
Back flashover
A short-circuit fault leads to which of the following?
Reduction in current
Excessive current flow
Power factor improvement
Zero sequence current removal
HRC fuse is designed to operate under:
Normal current
High frequency currents
Low power factor loads
Short-circuit condition
Gapless Metal Oxide Surge Arrester is preferred over expulsion type because:
It is cheaper
It requires no series gap and offers better protection
It has longer lifespan
It can handle DC fault
Which fault is most common in overhead transmission lines?
Single line-to-ground fault
Double line-to-ground fault
Three-phase fault
Line-to-line fault
For EHV systems, fuses are not preferred because:
They are cheap
They cannot interrupt very high fault currents reliably
They can be reset
They occupy less space
Which of the following reduces voltage surges in long transmission lines?
Series capacitor
Shunt reactor
Ground wires
Isolators
Which of the following is an advantage of HRC fuse compared to HV fuse?
Faster operation at low currents
High rupturing capacity and reliable arc quenching
Lower cost
No replacement needed after fault
A feeder relay detects a fault current of 500 A, while its pickup setting is 300 A. What will happen?
Relay remains inoperative
Relay trips the circuit breaker
Relay resets to normal
Relay signals alarm only
Overvoltage caused by switching operations is known as:
Switching surge
Power surge
Lightning surge
Surge impedance
Why are overhead ground wires placed above phase conductors?
To reduce corona
To intercept lightning strokes
To improve power factor
To increase insulation level
Why are Potential Transformers (PTs) used in protection schemes?
To step down current
To isolate faulty equipment
To step down voltage for relays and meters
To provide auxiliary supply
What is the main arc-extinguishing material in HRC fuses?
Sand or silica powder
Air
Oil
SF6 gas
Which of the following is a primary purpose of a protective scheme?
Increase system efficiency
Detect and isolate faults
Reduce transmission losses
Improve power factor
Earthing screen provides protection to:
Substations from direct lightning strokes
Transmission lines from corona
Underground cables from moisture
Generators from overheating
What is the preferred type of CB to be installed in extra high voltage ac system?
Bulk oil type CB
Air-blast CB
Vacuum CB
Sulphur hexafluoride (SF6) CB
The main goal of arc interruption is to:
Increase the arc temperature indefinitely
Prevent deionization of the gap
Stretch, cool and de-ionize the arc path so current is extinguished
Convert AC to DC during interruption
Which quantity directly causes an overcurrent relay to operate?
Excessive voltage
Reactive power
Current above the relay pickup setting
Frequency deviation
The fluids used in circuit breakers should be of:
high dielectric strength and thermal stability
non-inflammability
arc extinguishing ability
all of the above
Recovery voltage refers to:
Voltage across the breaker after the arc is extinguished when the system restrikes conditions are applied
Voltage inside the trip coil only
Voltage used to recharge the closing spring
Voltage across the motor starter
Which statement correctly explains why HVDC breakers often combine mechanical switches and power electronics?
Mechanical switches alone are sufficient for DC interruption
Power electronics are never used in HVDC breakers
Mechanical switches are only for cosmetics
Semiconductors can control and rapidly commutate the DC current into a path where mechanical interruption can take place at (near) zero current, combining speed and low loss
What is the primary function of a protective relay?
Store energy for system start-up
Measure system frequency only
Detect abnormal conditions and initiate isolation of faulty equipment
Convert AC to DC
SF6 gas is used in circuit breakers because it:
Has poor dielectric properties but low cost
Has excellent dielectric strength and arc-quenching capability
Is magnetic and helps extinguish arcs through attraction
Arc in a circuit breaker is primarily sustained by:
Continuous mechanical contact between contacts
Ionized gas (plasma) providing a conductive path between separating contacts
Chemical conduction through insulation
Magnetic fields alone
For proper coordination between a primary and its backup relay, which is desirable?
Backup relay should be faster than the primary
Backup relay should have a longer time delay than primary to allow primary to clear the fault first
Both should operate simultaneously always
Primary should never operate
In a minimum oil circuit breaker the oil is used:
To act as circuit breaking medium only
For circuit breaking and providing insulation
For providing insulation only
For none of the above purposes
In an oil circuit breaker the arc is interrupted mainly by:
Solid insulator placed between contacts
Evaporation and decomposition of oil producing hydrogen which blows and cools the arc and provides insulation
Evacuating the contact region to vacuum
Using a cathode ray tube
When a CT saturates during an external fault, a differential relay may:
Always operate correctly because CT saturation has no effect
Maloperate (false trip) or fail to operate depending on polarity and saturation behaviour
Convert the differential relay into a distance relay
Become an instantaneous overcurrent relay
A definite-time relay is characterized by which of the following?
Operating time decreases with increasing fault current
Operating time is fixed irrespective of fault magnitude
No intentional time delay
It measures impedance to operate
The re-striking voltage (VR) is best described as:
The supply voltage measured at the neutral only
The transient voltage that can cause the arc to re-ignite during the interruption process
The mechanical force on contacts
The capacitor charging voltage in the control circuit
Which of the following is NOT typically a basic signal-processing block inside a static relay?
Rectifier / signal conditioner
Comparator / decision logic
Mechanical cam and lever assembly for time settings
Electronic timer and trip driver
An induction-type overcurrent relay principally uses which physical phenomenon for operation?
Electrostatic attraction
Electromagnetic induction producing torque on a moving element
Chemical reaction
Piezoelectric effect
Air used in air blast circuit breaker must:
Be ionized
Be free from moisture
Have least CO2
Have oil mist
In relay coordination studies, the grading margin is:
The physical gap between relay contacts
The minimum time difference provided between primary relay operation and backup relay operation to ensure selectivity
The current rating of the CT
The maximum allowable voltage
The main advantage of vacuum circuit breakers is:
They require frequent gas refilling
They extinguish arcs in a vacuum and have very long contact life with low maintenance
They use oil to quench the arc
They are suitable only for DC circuits
In Kando system of track electrification, ________ is converted into ________.
1‑phase AC to DC
3‑phase AC to 1‑phase AC
1‑phase AC to 3‑phase AC
3‑phase AC to DC
Pantograph is used to:
Supply DC power
Collect current from overhead wire
Reduce sparking
Control braking
Speed–time curve is used for:
Energy consumption calculation
Efficiency improvement
Torque control
Brake testing
Why are DC series motors preferred for traction?
High efficiency at constant speed
Good torque at zero speed
Simple construction
No maintenance
The direct current system used for tramways has a voltage of about ________ volt.
750
1500
3000
2400
If a train consumes 500 kWh over 200 ton‑km, its specific energy consumption is:
2.5 kWh/ton‑km
0.25 kWh/ton‑km
25 kWh/ton‑km
5 kWh/ton‑km
Which factor is NOT considered in the selection of an electric motor?
Starting torque
Running cost
Ambient temperature
Motor color
Comparing pantograph and bow collector, pantograph is preferred because:
Lighter
Provides better contact at high speed
Uses less current
Cheaper
Multiple unit control in trains allows:
Driving multiple motors independently
Operating many locomotives from one point
Preventing braking
Reducing voltage
A pantograph collects current at 1500 V and 200 A. Power drawn is:
300 kW
200 kW
150 kW
30 kW
The speed/time curve for city service has no ________ period.
free‑running
coasting
acceleration
braking
Which system of electrification is best for long‑distance trains?
AC single phase 25 kV
DC 600 V
Composite 11 kV
Diesel‑electric
Which type of motor is most commonly used in electric traction?
DC series motor
Induction motor
Synchronous motor
Universal motor
Main traction system used in India are, those using
electric locomotives
diesel engine locomotives
steam engine locomotives
all of the above
The speed of a superfast train is
60 kmph
75 kmph
100 kmph
more than 100 kmph
In speed-time curve, coasting period is when
Power is supplied continuously
Speed is constant
Brakes are applied
Train moves without power
Why are catenary-contact systems preferred?
Simple and robust
Easy maintenance
Cost effective
All of the above
The return circuit for tram cars is through ......
neutral wire
rails
cables
common earthing
Which lamp works on the principle of incandescence?
Sodium vapour lamp
Mercury vapour lamp
Incandescent lamp
Fluorescent lamp
Which sensor is widely used in lighting control?
Pressure sensor
Motion sensor
Temperature sensor
Gas sensor
Which lamp gives bluish-white light?
Incandescent lamp
Mercury vapour lamp
Sodium vapour lamp
CFL
LED stands for?
Light Emission Device
Low Energy Device
Light Emitting Diode
Lighting Electronic Device
Which of the following is an energy-saving lamp?
Incandescent lamp
Sodium vapour lamp
CFL
Mercury vapour lamp
Which lamp has the shortest life span?
Incandescent lamp
Fluorescent lamp
CFL
LED
Which lamp gives yellowish light?
Sodium vapour lamp
Mercury vapour lamp
LED lamp
Fluorescent lamp
IoT in lighting systems helps in
Manual control
Automatic control
Increases heat
Reduces efficiency
Which lamp requires ballast for operation?
Incandescent lamp
Fluorescent lamp
LED lamp
Halogen lamp
Which lamp has highest luminous efficiency?
Incandescent
Fluorescent
Sodium vapour
LED
Which lamp emits UV radiation inside tube?
Fluorescent lamp
Incandescent lamp
LED lamp
Sodium vapour lamp
Illumination engineering deals with the study of?
Heating systems
Lighting systems
Cooling systems
Mechanical systems
The filament of incandescent lamp is made of?
Copper
Aluminium
Tungsten
Iron
The unit of luminous intensity is?
Watt
Lux
Candela
Lumen
Which lamp has electrodes coated with emissive material?
Fluorescent lamp
Incandescent lamp
LED
CFL
The unit of illumination is?
Lumen
Lux
Candela
Watt
Factory lighting is designed for?
Beauty
Safety and productivity
Decoration
Saving electricity only
The unit of luminous flux is?
Candela
Lux
Lumen
Watt
Fluorescent lamps use which type of coating inside the tube?
Phosphor
Glass
Copper
Aluminium
CFLs are replaced by which modern source?
LED
Sodium vapour lamp
Mercury vapour lamp
Incandescent lamp
Why is dielectric heating not preferred for metals?
Metals are good conductors
Metals are insulators
Metals do not reflect waves
Metals have high resistance
Resistance heating works on which principle?
Ohm's law
Faraday's law
Lenz's law
Coulomb's law
Compare induction heating with resistance heating. Which is more efficient for uniform bulk heating? (Variant)
Resistance heating
Induction heating
Both equally
Depends on material
For surface hardening of steel, the heating method applied is: (Variant)
Resistance heating
Induction heating
Dielectric heating
Infrared heating
Arc heating utilizes the principle of:
Induction
Electric arc discharge
Conduction
Radiation
Laser beam welding is suitable for:
Thick plates
Precise and micro welding
Low-cost mass welding
Large structural fabrication
Which welding method is best suited for joining dissimilar metals?
Resistance welding
Arc welding
Ultrasonic welding
Laser beam welding
Why is electric heating considered more efficient than conventional heating? (Variant)
Less heat loss and precise control
More heat loss and less control
It requires no insulation
It works at low temperatures
Eddy current heating is practically used in:
Cooking
Metal hardening
Plastic welding
Dielectric drying
Arc heating utilizes the principle of
Induction
Electric arc discharge
Conduction
Radiation
Coreless induction furnace is widely used because: (Variant)
It is cheap
It is suitable for large-scale melting
It has simple construction and uniform heating
It consumes less power
Which electric furnace is best suited for steel melting? (Variant)
Resistance furnace
Direct arc furnace
Indirect arc furnace
Dielectric furnace
Why is ultrasonic welding more advantageous than arc welding for thin metals? (Variant)
Less heat affected zone
Cheaper electrodes
Easier operation
No power required
In high-frequency heating, the main effect used is: (Variant)
Eddy current loss
Hysteresis loss
Skin effect
Dielectric loss
In resistance welding, what is the main factor influencing weld quality?
Electrode pressure and current
Arc length
Gas shielding
Laser beam focus
In electric arc furnace, excessive electrode consumption indicates:
Correct operation
Improper arc length and power factor
High efficiency
Low temperature
Indirect arc furnace differs from direct arc furnace in that:
Electrode touches the charge
Arc is struck between electrodes
Arc does not directly touch the charge
No electrode is used
Which of the following is an advantage of electric heating?
Low efficiency
High initial cost
Clean and pollution free
Slow response
In dielectric heating, heat is produced due to:
Joule effect
Dielectric losses
Eddy currents
Arc formation
Which of the following are main causes of overvoltages in power systems? Select all that apply.
Lightning strikes
Switching surges
Arcing grounds
Resonance conditions in transmission lines
Steady-state load current
Which of the following are common causes of faults in power systems? Select all that apply.
Insulation breakdown
Mechanical failures
Lightning
Contamination
Overloading of equipment
What is the primary purpose of protective schemes in a power system?
To detect abnormal conditions and isolate faulty sections to ensure continuity of supply
To increase generation capacity during peak demand
To reduce power factor penalties
To enhance billing and metering accuracy
Overhead ground wires are used to:
Intercept lightning strokes and divert them safely to ground
Carry communication signals above the conductors
Support the mechanical weight of phase conductors
Reduce corona loss by smoothing conductor surface
Select the causes of faults in power systems. Choose all that apply.
Lightning
Insulation breakdown
Mechanical damage
Short circuits
Improved grounding practices
The operating principle of a lightning arrester is to:
Provide a low-resistance path for surge currents to ground, thereby limiting overvoltage
Store excess energy in capacitors until the surge passes
Open the circuit breaker immediately on any overcurrent
Divert normal load current through a reactor to reduce spikes
The function of an earthing screen installed over a substation is to:
Shield equipment from lightning strokes by means of a grounded metallic mesh
Improve the power factor by providing reactive compensation
Reduce conductor sag during high temperatures
Serve as a communication antenna
Which statement best defines overvoltage?
Any system voltage higher than the rated value that persists for a short duration
Any drop in voltage below the rated value for a brief period
A permanent increase in rated system voltage for efficiency
Voltage variations due to load changes during normal operation
Which statements correctly describe direct and indirect lightning strokes? Select all that apply.
A direct stroke strikes the line directly
An indirect stroke induces voltages due to electromagnetic effects
A direct stroke only affects nearby lines via induction
An indirect stroke requires physical contact with the conductor
Which of the following are common types of faults in a power system? Select all that apply.
Single line-to-ground fault
Line-to-line fault
Double line-to-ground fault
Three-phase fault
Open-circuit fault between source and load
