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NHPC-JE’21 EE: Daily Practices Quiz
NHPC-JE’21 EE: Daily Practices Quiz 21-Sep-2021
Each question carries 1 mark.
Negative marking: 1/4 mark
Total Questions: 06
Time: 06 min.
Q1. A thermal protection switch provides protection against:
(a) Short-circuit
(b) Under voltage
(c) Over-voltage
(d) Over-load
Q2. What is the inductive reactance if the Q of a coil is 60, and the winding resistance is 5 Ω?
(a) 12 Ω
(b) 300 Ω
(c) 30 Ω
(d) 0.083 Ω
Q3. For protection of transformer against all kinds of incipient faults, which relay is used:
(a) Buchholz relay
(b) Earth-fault relay
(c) Over current relay
(d) All of the above
Q4. What type of earthing is used by transmission lines?
(a) Plate earthing
(b) Rod earthing
(c) Strip earthing
(d) Both (a) & (c)
Q5. Negative voltage regulation is indicative that the load is
(a) Inductive
(b) Capacitive
(c) Inductive or Resistive
(d) None of the above
Q6. A dynamometer wattmeter can be used for
(a) AC measurement only
(b) Both AC & DC measurement
(c) DC measurement only
(d) None of the above
SOLUTIONS
S1. Ans.(d)
Sol. A thermal protection switch provides protection against Over-load.
S2. Ans.(b)
Sol. Q=X_L/R=X_L/5=60
∴Inductive reactance=X_L=60×5=300 Ω
S3. Ans.(a)
Sol. Buchholz relay is used for protection against insulation failure of windings, core heating, fall of oil level etc.
S4. Ans.(c)
Sol. Strip earthing is used by transmission lines.
S5. Ans.(b)
Sol. (VR=(%R)cosϕ ±(%X)sinϕ)
+ → for lagging (inductive load)
– → for leading (capacitive load)
Maximum regulation at lagging pf
Minimum or zero or negative regulation at leading pf.
S6. Ans.(b)
Sol. A dynamometer wattmeter can be used for both AC & DC measurement.