Electrical Inspection, Testing and Certification Practice Exam

When testing EFLZ (Earth Fault Loop Impedance), what must be done with the main earthing conductor?

1. It must be disconnected then re-connected

2. It must be left connected

3. It must be replaced

4. It must be grounded

The correct answer is: It must be disconnected then re-connected

When testing Earth Fault Loop Impedance (EFLZ), it is essential to disconnect the main earthing conductor to obtain accurate readings. The reason for this is that the purpose of the EFLZ test is to measure the total impedance of the earth fault loop as it would exist during a fault condition. If the earthing conductor remains connected, it can influence the measurements by providing an alternate path for the test current. This could result in a lower impedance reading, which does not accurately represent the real conditions of an earth fault scenario. Disconnecting the main earthing conductor ensures that the testing is conducted under conditions that closely mimic an actual fault, allowing for a reliable assessment of the system's safety and functionality. In contrast, leaving the earthing conductor connected would compromise the integrity of the test results, while replacing it or grounding it are actions that do not pertain directly to the requirements of the EFLZ test process.