Electrical Drive System Protection MCQ [Free PDF] – Objective Question Answer for Electrical Drive System Protection Quiz

1. Relay is an electromechanical switch.

A. True
B. False

Answer: A

Relay is an electromechanical switch. It uses electrical signals as input and mechanical operation as output.

 

2. Mho relay is used in the medium transmission line.

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A. True
B. False

Answer: B

Mho relay is an inherent directional relay. It is used in the long transmission line. It is less affected by power surges.

 

3. Full form of LED is _____________

A. Light Emitting Diode
B. Light Emission Digital
C. Light Energy Diode
D. Light Energy Digital

Answer: A

The full form of LED is a light-emitting diode. It converts light energy into electrical energy. It works in the reverse bias region.

 

4. Inter turn fault can be detected by using __________

A. Oil circuit breaker
B. Split phase relay
C. SF6 circuit breaker
D. Vertical breaker

Answer: B

Inter-turn fault mainly occurs in the winding of the rotor side of the alternator. They can be detected by using the split-phase relaying technique.

 

5. Calculate the value of the fault impedance if the fault voltage is 2 V and the fault current is 4 A.

A. .5 ohm
B. .2 ohm
C. .4 ohm
D. .6 ohm

Answer: A

The value of the fault impedance is the ratio of fault voltage and fault current. It is expressed in ohms.

Z=V/I=2/4=.5 ohm.

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6. Reactance relay is used in _______

A. Medium line
B. Short transmission line
C. Lossless line
D. Long transmission line

Answer: B

Reactance relay is used in a short transmission line. The reactance relay is independent of the resistance value. It protects the short transmission line from any fault.

 

7. Load interrupter operated at ________

A. No-load
B. Full load
C. Half of the full load
D. One-fourth of the full load

Answer: B

A load interrupter is used to avoid overloading conditions. It separates the under-stressed area from the line. It operates at full load.

 

8. Calculate the maximum frequency for ASCI using the data: R=1 kΩ, C=1 μF.

A. 250 Hz
B. 280 Hz
C. 300 Hz
D. 320 Hz

Answer: A

The minimum time period for ASCI is a

4×R×C=4×1×1×.001=4 msec.

The total time is the sum of charging and discharging time. The maximum frequency is 1÷f=250 Hz.

 

9. Calculate the PIV for the Full-wave bridge rectifier if the peak value of the supply voltage is 50.

A. 72.5 V
B. 72.8 V
C. 70.7 V
D. 76.1 V

Answer: C

The peak inverse voltage for the Full-wave bridge rectifier is

Vm = √2×230=70.7 V.

The peak inverse is the maximum negative voltage across the thyristor.

 

10. In single-phase, RLE load, calculate the Peak inverse voltage using the data: (Vs)r.m.s = 9 V, f = 50 Hz, E = 40 V.

A. 52.2 V
B. 52.7 V
C. 59.7 V
D. 52.9 V

Answer: B

In a single-phase, RLE loads the peak inverse voltage across the thyristor

VT = Vm+E = 52.7 V.

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