You can check whether the train is cancelled or not by checking the current status of the tikcet on the internet.
If the train is marked as "CANCELLED" in PRS full refund is permissible in case the ticket is cancelled within 72 hours of the scheduled departure of the train.Customer can himself make such cancellations of e-tickets through internet.
If such cases are not cancelled within 72 hours of scheduled departure of the train, customers should file TDR with option 'Train cancelled' to process the refund through TDR.