How can charging current be understood intuitively?
"For a more precise estimate, use manufacturer’s data to sum up 
the different circuit elements that contribute to charging 
currents, such as cable capacitance per 100 feet, surge 
arrestors, motors, etc"

Charging current happens in any electrical condition, its the total capacitance of the whole system in question.  You see it profoundly in transmission lines due to the insane capacity of long wire lengths.  But it basically exists everywhere just to lesser extent.  Hope that helped, its basically spec info that you would have to gather based on the install in question.  as for the formula that will provide that, that would be another thing.