Solution : https://service.sap.com/sap/support/notes/1386833 (SAP Service marketplace login required)
Key words : 
runtime error         convt_codepageexception                cx_sy_conversion_codepagethe system, import account statement files, attached advance corrections, find detailed information, system code page, unicode code page, user parameter ucp, account statement, unicode system, solution import
Related Notes : 
       
| 758870 | Account statement: Character set when the file is uploaded |