Which potential would you apply when performing an insulation resistance acceptance test on 300V rated cable?

When performing an insulation resistance acceptance test on a cable rated for 300V, it is important to apply a test voltage that is appropriate and safe for the insulation level of the cable. The general guideline is to apply a test voltage that is at least twice the rated voltage of the cable to effectively assess the integrity of the insulation.

In this case, the cable is rated for 300V, so a suitable test voltage would ideally be higher than that. The option of 1000VDC is a commonly used value for testing insulation on cables in this voltage range. It provides a robust test that can reveal potential weaknesses in the insulation. Additionally, it adheres to industry standards that recommend higher testing voltages to ensure that the insulation can handle higher than its rated voltage in practical applications.

While options such as 250VDC and 500VDC are lower than what is typically recommended for a 300V rated cable, they would not provide a sufficient margin for evaluating the insulation's protective qualities against potential breakdowns. Test voltages that are too close to the rated voltage may not effectively test the insulation's performance under fault conditions. Thus, applying 1000VDC is the correct practice to ensure a comprehensive assessment of the cable's