MES Departmental • 2025 • Paper-II
The primary consideration for a transmission substation site is:
A)
Proximity to residential areas
B)
High population density
C)
Proximity to load centers & transmission line corridors
D)
Close to airports
Option C is correct: Proximity to load centers & transmission line corridors.
MES Departmental • 2025 • Paper-II
What is a common maintenance task for Power Transformers in outdoor substations?
A)
Changing the tank paint every year.
B)
Checking oil level, colour, and moisture content, plus oil testing.
C)
Removing all bushings for cleaning.
D)
Reducing the load to below 50%.
Option B is correct: Checking oil level, colour, and moisture content, plus oil testing..
MES Departmental • 2025 • Paper-II
How does earthing contribute to system stability?
A)
By introducing resistance in the neutral
B)
By providing a stable reference point (zero potential) for the system
C)
By increasing system impedance
D)
By creating an isolated neutral
Option B is correct: By providing a stable reference point (zero potential) for the system.
MES Departmental • 2025 • Paper-II
Which of the following power semiconductor devices has the highest switching speed?
A)
BJT
B)
IGBT
C)
Power MOSFET
D)
SCR
Option C is correct: Power MOSFET.
MES Departmental • 2025 • Paper-II
A major constraint for substation location is proximity to:
A)
River crossings
B)
Industrial zones
C)
Airports & defense establishments
D)
Agricultural lands
Option C is correct: Airports & defense establishments.
MES Departmental • 2025 • Paper-II
In a power triangle, what is the relationship between active power (P), reactive power (Q), and apparent power (S)?
A)
P + Q = S
B)
P² + Q² = S²
C)
P = Q + S
D)
S² + Q² = P
Option B is correct: P² + Q² = S².
MES Departmental • 2025 • Paper-II
What is the primary function of an inductor in an AC circuit?
A)
To store energy in a magnetic field
B)
To oppose a change in circuit current
C)
Both (a) and (b)
D)
To convert electrical energy to mechanical energy
Option C is correct: Both (a) and (b).
MES Departmental • 2025 • Paper-II
In a series connection of resistors, what happens to the current across each resistor?
A)
Increases
B)
Decreases
C)
Remains the same
D)
Initially increases and then decreases
Option C is correct: Remains the same.
MES Departmental • 2025 • Paper-II
What is the primary instrument used specifically for measuring earth resistance?
A)
Ammeter
B)
Voltmeter
C)
Earth Tester (or Ground Resistance Tester)
D)
Frequency Meter
Option C is correct: Earth Tester (or Ground Resistance Tester).
MES Departmental • 2025 • Paper-II
The function of a protective relay is to:
A)
Detect the fault and initiate the operation of the circuit breaker
B)
Absorb the fault current
C)
Step down the voltage for metering
D)
Provide an alarm only during a fault
Option A is correct: Detect the fault and initiate the operation of the circuit breaker.
MES Departmental • 2025 • Paper-II
Why are off-load tap changers operated only when the transformer is de-energized?
A)
To prevent sparking
B)
To avoid damaging the mechanism
C)
To ensure safety and proper contact engagement
D)
They don’t require power
Option C is correct: To ensure safety and proper contact engagement.
MES Departmental • 2025 • Paper-II
Which protection scheme is generally recommended for Power transformers with a rating above 5MVA?
A)
Over-current protection
B)
Differential protection
C)
Restricted Earth Fault protection
D)
Buchholz relay
Option B is correct: Differential protection.
MES Departmental • 2025 • Paper-II
Where should lightning arresters be installed for optimal transformer protection?
A)
Inside the transformer tank
B)
At the termination point of overhead lines leading to the transformer
C)
On the ground below the transformer
D)
Only on the low-voltage side
Option B is correct: At the termination point of overhead lines leading to the transformer.
MES Departmental • 2025 • Paper-II
A freewheeling diode in a phase-controlled rectifier is used to:
A)
Improve the power factor
B)
Provide a path for inductive load current
C)
Reduce the reverse breakdown voltage requirement
D)
Increase the output voltage
Option B is correct: Provide a path for inductive load current.
MES Departmental • 2025 • Paper-II
What is the primary purpose of switchgear in an electrical power system?
A)
To generate electricity
B)
To step up or step down voltage levels
C)
To protect, control, and isolate electrical equipment
D)
To measure power consumption
Option C is correct: To protect, control, and isolate electrical equipment.
MES Departmental • 2025 • Paper-II
The algebraic sum of voltages (potential differences) around any closed path in a network is equal to:
A)
Infinity
B)
1
C)
0
D)
Negative polarity
Option C is correct: 0.
MES Departmental • 2025 • Paper-II
Which of the following is a method to reduce skin effect losses in a transmission line?
A)
Using solid conductors
B)
Increasing the frequency
C)
Using stranded conductors
D)
Increasing conductor resistance
Option C is correct: Using stranded conductors.
MES Departmental • 2025 • Paper-II
What is the primary purpose of laminating a transformer core?
A)
To increase flux density
B)
To reduce eddy current losses.
C)
To improve insulation
D)
To increase mechanical strength
Option B is correct: To reduce eddy current losses..
MES Departmental • 2025 • Paper-II
An instantaneous over-current relay operates:
A)
With a time delay that is inversely proportional to the current
B)
Immediately when the current exceeds a predetermined value
C)
After a fixed, definite time delay
D)
Only for earth faults
Option B is correct: Immediately when the current exceeds a predetermined value.
MES Departmental • 2025 • Paper-II
Kirchhoff’s current law is applicable to only
A)
closed loops in a network
B)
electronic circuits
C)
junctions in a network
D)
electric circuits
Option C is correct: junctions in a network.
MES Departmental • 2025 • Paper-II
The maximum value of an alternating voltage or current in a cycle is known as its
A)
RMS value
B)
Peak-to-peak value
C)
Amplitude
D)
Average value
Option C is correct: Amplitude.
MES Departmental • 2025 • Paper-II
Which component absorbs moisture from the air during a transformer’s “breathing”?
A)
Conservator
B)
Radiator
C)
Breather (Silica Gel)
D)
Buchholz Relay
Option C is correct: Breather (Silica Gel).
MES Departmental • 2025 • Paper-II
If a section of LT ABC is experiencing frequent faults due to illegal tapping (hooking), which inherent feature of ABC helps mitigate this issue?
A)
The use of a messenger wire
B)
The insulated nature of all conductors
C)
Its high mechanical strength
D)
Its ability to be run concurrently with communication lines
Option B is correct: The insulated nature of all conductors.
MES Departmental • 2025 • Paper-II
What is magnetizing inrush current?
A)
Current during heavy load
B)
Current during fault
C)
A transient rush of current (6 to 8 times rated current) when first energized
D)
Current during unloading
Option C is correct: A transient rush of current (6 to 8 times rated current) when first energized.
MES Departmental • 2025 • Paper-II
The common type of storage battery generally used in electric power stations is the:
A)
Nickel-cadmium battery
B)
Zinc-carbon battery
C)
Lead-acid battery
D)
Lithium-ion battery
Option C is correct: Lead-acid battery.
