I bought an extra power adapter for my XPS earlier this year. Even thought there were cheaper 3rd party alternatives, I bought directly from Dell because I wanted good warranty (1 year for hardware and accessories). However, when I tried to get service for the adapter because the rubber covering the wires is coming apart where it meets the adapter, they are telling me, the hardware warranty only applies to laptop and accessories purchased at the same time. If you bought the accessory separately, it is not covered. This is EXTREMELY deceptive. There is no text about this during the purchase. I could have saved a lot of money by buying a 3rd party adapter on Amazon.
Be aware of you are thinking of buying accessories for your laptop. Do not do it through Dell.
Thanks for posting. Apologies that the information regarding your accessory warranty was not clear.
Parts and Accessories from Dell have at least a 90 day warranty, as explained here. While your post does not mention the part number of the product you purchased, this example has a 3 year warranty. However, normal wear and tear is not covered by warranty. From your post, the damage you mentioned would be considered normal wear and tear, as explained by this Dell knowledge base article.
Hopefully this information helps to explain things more clearly for you.
If you need additional assistance, please contact me privately. Be sure to include your personal information (name, address, telephone, email) and your computer's service tag number in your message. Thanks.