🔍 Key Concepts

• Insulation resistance trending over time (look carefully at the plotted megohm values from 2005–2010) • Difference between an acceptable minimum insulation resistance and a rapidly deteriorating trend • How a sudden sharp drop in megger readings affects maintenance planning for a motor

💭 Think About

• Compare the 2010 megger reading with the earlier years: is the change gradual or sudden, and what does that usually indicate about insulation condition? • Even if a reading is still above a common minimum value, what does a strong downward trend tell you about future reliability and risk of failure? • Ask yourself whether simply testing more often solves the underlying problem, or whether a different kind of action is normally planned when a big drop occurs.

✅ Before You Answer

• Verify the numerical value of the 2010 insulation resistance on the chart and how many times lower it is than previous readings. • Check whether the earlier readings were relatively stable and all in the same general range, compared with the 2010 point. • Decide whether a prudent engineer would focus on increased monitoring, no action, planning refurbishment/replacement, or expecting many more years of life when seeing this kind of sharp decline.