Which of the following is listed as a cause of an Earth Fault trip?

• A. Damage, Water Insulation
• B. Diode Fault
• C. Overload
• D. Short Circuit

Answer: (A)

Earth fault protection trips when current leaks from a live conductor to earth. This leakage appears when insulation is damaged or moisture (water) bridges conductors to ground, creating a path for current to flow to earth. The earth-fault relay senses this imbalance and trips to isolate the circuit, protecting people and equipment.

A diode fault is a component issue, not a leakage path to earth. Overload involves excessive current in the normal path and is typically cleared by overcurrent protection, not by earth fault protection. Short circuit can cause high current as well, but it’s usually detected by overcurrent protection unless it explicitly creates a leakage to earth, which isn’t the typical cause cited here.