There is a 7 hour delay in departure for todays train, but for 17/07 the official site doesnt show any delay. Please check tomorrow.
If u have confirmed tatkal ticket then u will only get 25% of your fare back if cancelled before 24 hrs of scheduled departure as printed on your ticket. If still in WL you will get full refund les Rs 20 clerkage charge.
But if the train departs from the station after 3hrs of scheduled departure, then you can cancel this ticket for full refund.