Which of the following statements is true regarding the setting of an earth fault relay?

Explanation: An earth fault relay is designed to detect ground faults or leakages in a system by monitoring current imbalances. The setting of the relay is crucial for ensuring that it detects earth faults accurately without responding to normal operating conditions.

Here’s why the setting should always be less than the rated full-load current:

• Earth fault conditions typically involve a small portion of the total system current flowing through the ground. The fault current is usually much lower than the full-load current of the system.
• If the setting of the earth fault relay is equal to or greater than the rated full-load current, it may not detect the relatively small earth fault currents, thus failing to trip in time.
• Setting the relay to a value less than the rated full-load current ensures that even small earth fault currents are detected, offering timely protection to the system.
• The relay should be set at a value that is lower than the full-load current but higher than the normal leakage or imbalance current to avoid nuisance tripping during normal operation.
   

Conclusion: The earth fault relay setting should always be less than the rated full-load current to ensure the relay can detect even small ground faults effectively and provide adequate protection to the system.