How can I size my current carrying trace width for surge current? any standard or formula?
For a surge rating, you need to do an adiabatic calculation. This is where the heat generated in the copper simply raises its temperature, and has not yet had time to dissipate into the air or the board. This is also known as an I2t rating.
First choose a starting temperature, and a maximum temperature. The difference between them gives you the allowable temperature rise you can use to absorb the surge energy. The starting temperature might be your ambient, or your max operating temperature, or the elevated temperature remaining from your last surge. The maximum temperature might be the melting point (for fuse wire), or for PCB perhaps the delaminiation temperature, or the max temperature you might encounter when soldering. Or a lower temperature than those, depending on whether you are trying to meet any particular standards.
As you see, you need to start off with some assumptions.
Once you know the maximum temperature rise available to you, the rest is fairly easy. From the dimensions of the track, compute the volume, hence mass, hence heat capacity of the track copper in Joules/degree. From the dimensions, compute the resistance, hence energy dissipated with your surge duration and magnitude. Equate the two.
A nice tool that can help with PCB design is Saturn PCB Toolkit. Besides providing the calculators has all the references to formulas as well.