Blistering of insulation indicates a lot of heat, it may have been caused by lightning, or poor connection. The conductor could be compromised at any point if it got direct hit by lightning. I do not know if it is aluminum or copper, but aluminum conductors will turn into an aluminum oxide powder if exposed to water due to failed insulation. You might end up replacing the whole segment, but best to hire an electrician to diagnose, they will have the proper equipment
What is the amp rating of the upstream breaker and gauge of wire; if smaller might just replace whole line yourself.