What indicates a failing Polarization Index result?

A Polarization Index (PI) test is an important diagnostic tool used primarily to assess the insulation condition of electrical equipment, such as motors and transformers. The PI is calculated as the resistance of the insulation measured over a specific time frame, typically 10 minutes to 1 minute, divided by the insulation resistance measured at the same time.

A result of less than 2 indicates that the insulation is likely degrading or has issues that could lead to failures or downtime. When the Polarization Index is below this threshold, it suggests that the insulation has a high level of moisture or contaminants, which can lead to electrical leakage and, ultimately, failure of the equipment.

A grade above 2, on the other hand, generally indicates that the insulation is in good condition. A grade of exactly 2 is often seen as a borderline or acceptable level but not necessarily indicative of failing insulation. Results between 1 and 2 further suggest concerning insulation quality, yet still not as definitive as a result under 2, which unequivocally signals a potential failure risk. Thus, the correct choice highlights a crucial aspect of evaluating insulation health through PI testing.