It is difficult to say exactly from your photos, but I suggest you are looking at a lightning arrester that is failing. Any heat above ambient in these suggests impending failure which can occur catastrophically. I'd suggest you confirm your finding and consider scheduling replacement.
I was invited to present a paper recently at the Doble conference on the topic of inspecting lightning arresters. If you, or other readers are interested, I can provide a copy to you.
Thermally Yours,
John
ASNT NDT Level III #48166
The Snell Group
www.thesnellgroup.com
www.thermalsolutions.org
800-636-9820