What is a common indication of winding overheating in a generator’s insulation system?

• A. Increasing insulation resistance drop, discoloration or odors
• B. Decreasing insulation resistance only
• C. Lower operating temperature
• D. Higher ambient humidity

Answer: (A)

Overheating of the winding damages the insulation, so you’ll often see electrical and physical clues together. The insulation resistance tends to fall as the insulation degrades and leakage paths form, and you may also notice physical signs like discoloration of the insulation and a burnt or chemical odor from overheated materials. This combination—a drop in insulation resistance plus discoloration or odors—is a common, practical indication that the winding has overheated.

The other possibilities don’t fit as well because a temperature reduction isn’t a sign of overheating, and while environmental humidity can affect insulation, it isn’t a direct indicator that the winding itself has overheated.