Transformer Core and Clamp Grouded

As far as I know, the bottom part of the transformer clamp is not grounded. However, the upper transformer clamp is grounded at one point. Basically, the transformer core and clamp are grounded at one point, although there is an insulation material between them.

What's the implication if the bottom clamp touching the core? Let's say due to insulation failure between clamp and core?

Why is only the upper part of the clamp grounded?
All of it ! Are you referring to a specific transformer ? Or a some photo in your possession ? Is it related to specific equipment in the Power Plant identified with your forum name ?