I want to know about the Cu wire specification for insulation & size

Be more specific, use more words to describe the information you are seeking.

Go to a place such as Lowe's, and there are dozens of sizes and types types of building wire. Then you have automotive, high voltage, magnet, telecommunication, mining cable, etc. The conductor itself is either pure copper or copper with a coating of tin. Aluminum is used too. There are specifications for the diameter of solid wire. It also comes stranded, 7, 19, or more strands. I couldn't begin to say how many different types of insulation there are. When I managed a vinyl compounding plant, we produced a couple dozen different compounds although some of them were for molding connectors and the outer jacket of cables. Then there is rubber, polyethylene, CPE, semi conductive PE, cross linked PE, nylon, etc. So tkrussel is right, we need more details.