What happens to the fiber inside a cutout barrel each time it fails?

When a cutout barrel fails, the fiber inside experiences erosion due to thermal and mechanical stressors associated with electrical faults or overloads. Each time there is a failure, the intense heat generated can break down the fiber material. This breakdown results in the gradual removal or degradation of the material, leading to a decrease in its structural integrity. Over time, as failures occur, the fiber is progressively worn away, impacting its performance and reliability.

In contrast, the other options do not accurately represent what occurs during a failure scenario. The density of the fiber does not increase as the failure occurs, and it is not completely replaced with each failure—such replacements typically happen after multiple failures or a significant event. The fiber doesn’t remain unchanged either, as the erosive effects are a direct consequence of operational stresses.