Junior Engineer (Electrical/Electronics) MCQs – Series 5 (Q61-70)
Q61. The main purpose of a surge arrester in a power system is to:
- A) Reduce transmission line losses
- B) Improve system power factor
- C) Protect equipment from lightning and switching surges
- D) Regulate steady-state voltage
Answer: C
Surge arresters divert high-magnitude transient overvoltages (lightning/switching surges) safely to ground, protecting connected equipment.
Q62. Corona loss in overhead transmission lines increases with:
- A) Larger conductor spacing only
- B) Lower line voltage
- C) Smaller conductor diameter and higher line voltage
- D) Larger conductor diameter
Answer: C
Corona occurs when the electric field at the conductor surface exceeds the breakdown value, favored by thin conductors and high voltages.
Q63. The main reason electrical power is transmitted at high voltage is to:
- A) Reduce current and thus reduce I²R losses
- B) Increase conductor cross-section
- C) Increase current and reduce voltage drop
- D) Reduce insulation requirements
Answer: A
For a given power, higher transmission voltage means lower current, which reduces resistive (I²R) losses in the line.
Q64. Which type of insulator is typically used at the dead ends and sharp turns of transmission lines?
- A) Suspension insulator
- B) Pin insulator
- C) Strain insulator
- D) Shackle insulator
Answer: C
Strain insulators are designed to withstand the mechanical tension at line dead-ends, terminations, and sharp angle points.
Q65. The Ferranti effect on transmission lines refers to the condition where:
- A) Receiving-end voltage exceeds sending-end voltage on a lightly loaded long line
- B) The line is heavily loaded and voltage drops sharply
- C) Sending-end voltage always exceeds receiving-end voltage
- D) Voltage remains constant regardless of loading
Answer: A
On long lines under light or no load, the line’s capacitance causes the receiving-end voltage to rise above the sending-end voltage.
Q66. The purpose of bus-bar protection in a substation is to:
- A) Reduce transmission losses
- B) Improve the system’s power factor
- C) Regulate the substation voltage
- D) Quickly isolate a faulty section of the bus to protect connected equipment
Answer: D
Bus-bar (differential) protection detects faults on the busbar and rapidly isolates the affected section to limit damage.
Q67. Economic load dispatch in power system operation aims to:
- A) Equalize the loading on all generating units
- B) Maximize transmission losses across the network
- C) Minimize only the system voltage
- D) Minimize total generation cost while meeting system demand
Answer: D
Economic dispatch allocates generation among available units to meet demand at the lowest overall fuel/operating cost.
Q68. The most common method for grounding the neutral point of distribution transformers is:
- A) Leaving the neutral completely floating
- B) Solid or resistance grounding
- C) Capacitive grounding only
- D) Grounding through an air gap only
Answer: B
Solid or resistance (impedance) grounding of the neutral is standard practice to limit fault currents and stabilize system voltage.
Q69. Which protective relay operates by comparing the current entering and leaving a protected zone?
- A) Overcurrent relay
- B) Distance relay
- C) Buchholz relay
- D) Differential relay
Answer: D
A differential relay compares currents at two ends of a protected element and operates when there is a significant mismatch, indicating an internal fault.
Q70. The main function of a Buchholz relay is to:
- A) Measure the load current of the transformer
- B) Improve the power factor of the transformer
- C) Regulate transformer output voltage
- D) Protect oil-filled transformers from internal faults by detecting gas accumulation
Answer: D
Mounted between the transformer tank and conservator, a Buchholz relay detects gas generated by incipient internal faults and can trip the circuit.
Pages:
1 2 3 4 5 6 7 8 9 10 11 12
