Can any meter be PT connected?
Any AC meter can be used with a potential transformer. At some voltage level, you may find that it is not standard practice to use PTs, but 6.6 kV is probably within the range where they are commonly used. A search for PTs to use will tell you that. You can buy panel meters designed for specific PT ratios and voltage ratings. That type of meter will read the primary voltage directly without having to calculate. That is the kind of meter you should probably be looking for.

Note that potential transformers and current transformers are also called instrument transformers. Meters that display the primary voltage or current are often referred to as "PT rated" or "CT rated." Panel meters used to display power distribution level values are sometimes called "switchboard meters" or "switchboard instruments."

The better instrument manufacturers should have information about meter ratings, how to order etc.