Electrical Inspection, Testing and Certification Practice Exam

Which test proves automatic disconnection of the supply?

1. Insulation resistance test

2. EFLZ - Earth fault loop impedance

3. Continuity test

4. Functional test

The correct answer is: EFLZ - Earth fault loop impedance

The Earth Fault Loop Impedance (EFLZ) test is specifically designed to verify the effectiveness of the protective earthing system, ensuring that, in the event of a fault, the system will effectively disconnect the electrical supply. This is crucial for safety, as it minimizes the risk of electric shock and fire hazards. The EFLZ test measures the total impedance of the earth fault loop, which includes the source impedance and the earth connection. By doing so, it determines whether the protective devices (such as circuit breakers or fuses) will operate correctly under fault conditions. A low impedance indicates a quicker disconnection of the supply during a fault, confirming that the safety mechanisms are functioning as intended. Other testing methods, while valuable in their own right, do not specifically address the disconnect mechanism in the same manner. The insulation resistance test assesses the condition of the insulation but does not pertain directly to supply disconnection during a fault. The continuity test verifies that the earth connections are intact but doesn’t measure the effectiveness of the disconnect operation under fault conditions. The functional test confirms that devices operate correctly but does not confirm the automatic disconnection response during a fault scenario. Therefore, the EFLZ test stands out as the method that directly proves the automatic dis