My answer is based on several assumptions and the National Electrical Code.
Seems to me that you need to go back and check your calculations or I am misunderstanding what you are asking. Without doing calculations on the wire, but looking up 550 amps on the tables, it would require a 1250 kcmil (32.74 mm dia, 633 mm^2) conductor.
A 1.06 mm dia wire is 18 AWG and rated for 14 amps at 90 degrees C, while a 50 mm^2 are cable would be closest to a #1/0 AWG and rated for 150 amps at 75 degrees C.
So are we dealing with a Motor or someother device with an in rush current of 550 amps? It makes a huge difference.
Is this is for a product that is going into production, or a one time sizing? If production you need to talk to someone above you for direction, you may end up with something that is non-listable, but may be a hazard o life and property.
I am making the assumption that you are a young (in the feild, not neccesarily age or time engineering in other areas of the feild) engineer (based on your use of the term RMS), not just someone unconnected with the electrical field. If you are a young engineer, please find a good old salt of the earth licensed electrician (or an electrical engineer in the feild) to work with to help you with all the things they don't teach us in school in this area of the electrical field. Specific education in this area is needed and it helps alot to get out there and get your hands dirty. Also, if you are an engineer stick around and learn. If you are not, you are way in over your head.
I sure hope that the little catch phrases translate well, just seeing that you are from China.
