🔍 Key Concepts

• Difference between uncorrected and temperature-corrected insulation resistance readings • Industry practice of basing maintenance decisions on the trend of corrected readings, not a single low uncorrected value • Looking for a consistent downward trend or a drop below an acceptable minimum value

💭 Think About

• On which curve (A or B) should you base the decision to refurbish/replace: the raw readings or the temperature-corrected readings? • Across the years shown, does the corrected curve ever show a clear, steady decline or fall significantly below its initial level? • If one or two points on the uncorrected curve are low, but the corrected curve stays high and fairly flat, what does that suggest about the actual condition of the insulation?

✅ Before You Answer

• Carefully trace Curve B (Corrected) from 2004 through 2011 and compare its values to the first year on the chart • Check whether any corrected reading falls to about half or less of the initial corrected reading, or shows a sustained downward drift • Confirm whether any apparent ‘bad’ year on Curve A is simply due to temperature effect, as shown by Curve B staying near its original value