An industrial electrician uses an insulation resistance tester on a three-core cable. The measured resistance between core and earth is 900 megaohms. What does this value indicate about the cable's insulation condition?

Question

Prepp Team · Accepted Answer

To determine the condition of a cable's insulation, an insulation resistance tester is used. In this scenario, the resistance measured between the core and earth is 900 megaohms.

Here's the step-by-step explanation:

The insulation resistance test is a common method to evaluate the effectiveness of a cable's insulation. A higher resistance indicates better insulation quality.
The measured resistance value of 900 megaohms is considered very high. In typical scenarios, an insulation resistance above 1 megaohm is generally acceptable, with values significantly above this threshold indicating excellent insulation condition.
The options provided in the question describe various states of insulation:
- Severe moisture ingress requiring drying: This would typically result in a much lower resistance value.
- Insulation breakdown needing replacement: This also implies inadequate resistance, usually well below 1 megaohm.
- Good condition and safe for operation: High resistance like 900 megaohms suggests this condition.
- Unsuitable for industrial environments: The given high resistance does not support this claim, as it implies the cable has good strength.

Based on the evaluation above, the correct interpretation of the 900 megaohm resistance measurement is that the insulation is in good condition and safe for operation.