Hi...
How to find the capacitor current withstanding capabilities?
In my project I have used 100uF/63V capacitor for 15V constant voltage.
When the fault occurs 30A current will flow into the capacitor. will it withstand?

 

It's pretty hard to get 30A to flow through a cap, though doable. Shoot, it's pretty hard to get 30A for flow from DC.

Remember a cap is a lot like a resistor for AC, it has reactance (instead of resistance), which will limit most currents nicely.

So for your senario you need frequency as well as capacitance to set up the problem. Other than that things like lead diameter will predominate (except for high frequency AC, where the skin effect becomes of major importance). These kind of problems almost always have more variables than their DC equivalents.