Aux 1 Unit 13 Q4

1 / 10

What limitation should be considered when using an RCD for earth fault detection?

B) RCDs can only detect faults in high-voltage systems.

D) RCDs are very difficult to install.

C) RCDs may not trip if the fault current is below their sensitivity threshold, potentially leaving minor earth faults undetected.

A) RCDs are not effective at detecting low-current earth faults.

2 / 10

What is the purpose of using a Megger (insulation resistance tester) in detecting earth faults within a distribution system?

C) To monitor the system's voltage fluctuations

A) To increase the current in the system

D) To reduce the insulation's effectiveness

B) To apply a high DC voltage to the system's insulation and measure the resistance, identifying any potential breakdowns that could lead to earth faults

3 / 10

What is the primary function of an Earth Leakage Circuit Breaker (ELCB) or Residual Current Device (RCD) in detecting earth faults?

D) To prevent the system from operating under high loads

C) To increase the current in the system

B) To detect imbalance between the live (phase) and neutral conductors, indicating a possible earth fault

A) To monitor and control the voltage output of the system

4 / 10

Why is insulation resistance testing important for detecting earth faults in electrical systems?

B) It identifies weak or deteriorating insulation that could cause earth faults, allowing preventive maintenance to be performed before a fault occurs.

D) It decreases the resistance of the insulation.

A) It measures the current flow in the circuit.

C) It increases the power output of the system.

5 / 10

What is a key advantage of using RCDs for detecting earth faults in a distribution system?

A) They are more expensive than other methods.

D) They are difficult to install and maintain.

B) They provide automatic protection by disconnecting the circuit as soon as an earth fault is detected.

C) They only work at very high voltages.

6 / 10

How does an RCD respond when it detects an earth fault in the distribution system?

A) It increases the system's voltage.

B) It disconnects the circuit by tripping to prevent electric shock or equipment damage.

D) It reduces the current in the system.

C) It sends a warning signal but keeps the circuit active.

7 / 10

In what type of systems are RCDs or ELCBs particularly important for detecting earth faults?

B) Systems with significant exposure to moisture, such as outdoor installations or bathrooms, where the risk of electric shock is higher

C) High-voltage transmission systems

A) Systems where insulation is constantly monitored

D) Systems with no grounding

8 / 10

Which of the following readings on a Megger would suggest a potential earth fault due to poor insulation?

B) A very low resistance reading (e.g., below 1 MΩ)

C) A zero voltage reading

A) A very high resistance reading (e.g., above 1 MΩ)

D) A high current reading

9 / 10

What is a significant advantage of using a Megger for detecting earth faults?

B) It provides a quantitative measurement of insulation resistance, helping to pinpoint potential faults and assess the overall health of the electrical insulation.

C) It automatically repairs faults.

D) It only works on high-voltage systems.

A) It requires no maintenance.

10 / 10

When conducting insulation resistance testing with a Megger, what safety precaution is essential?

D) Avoid using any protective gear.

A) Ensure the circuit is live before testing.

B) Ensure the circuit is isolated and discharged before testing to prevent electric shock and equipment damage.

C) Increase the voltage during the test.

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