Electrical Installation Level 2 Practice Test

What is the purpose of insulation resistance testing between live conductors and earth after wiring repairs?

To verify that insulation remains intact and there is no path for leakage or current leakage to earth. To measure earth resistance. To test RCD trip time. To check continuity of earth conductor.

Correct Answer:

To verify that insulation remains intact and there is no path for leakage or current leakage to earth.

Explanation:

The main idea here is to verify that the insulation between live conductors and earth remains intact so there isn’t a leakage path to earth. After wiring repairs, applying a high DC voltage between each live conductor and earth with a megohmmeter lets you measure the insulation resistance. A high resistance (in the megaohms) means the insulation is still good and there’s no unwanted current path to earth. A low resistance signals a leakage path or damaged insulation that could allow fault current to reach earth, posing shock or fire risk and requiring repair. This test specifically checks insulation integrity, not earth resistance, RCD trip time, or continuity of the earth conductor, which are different checks.

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