What might a low Polarization Index indicate about insulation?

A low Polarization Index (PI) often signifies that insulation may have deteriorated or is compromised, with one common cause being moisture ingress. The PI is calculated by measuring the insulation resistance over time, typically taking readings at 1 minute and 10 minutes. A low PI indicates that the resistance does not increase substantially over this time, which can suggest that there is a pathway for moisture to enter or that the insulation material itself has absorbed moisture.

Moisture ingress can lead to a reduction in insulation resistance, making it less effective at preventing electrical leakage. This reduced effectiveness can increase the risk of equipment failure, electrical hazards, and compromised operational efficiency. In contrast, a high PI value would reflect insulation that is in good condition, with minimal moisture presence.

While other factors may contribute to a low PI, such as insulation breakdown due to aging or overheating, the presence of moisture is a significant and common concern. Hence, when a low PI is observed, it is crucial to investigate potential moisture issues in the insulation system.