To work out the current, you need the power factor (and efficiency if it is a motors, as your kW is the output power):
Current = 530,000/(3x230xpower factor), at a power factor of 0.95 = 808 A
To understand the calculation, you can read the post: Three Phase Current  Simple Calculation
The cable size depends on the installation method and what voltage drop you will accept.
You can use the sites cable sizing tool to work this out.
