Data refresh to schedule an automatic import of updated data from those original sources
PowerPivot data in an Excel workbook can originate from multiple external data sources, including external databases or data files that you access from remote servers or network file shares. For PowerPivot workbooks that contain imported data from connected or external data sources, you can configure data refresh to schedule an automatic import of updated data from those original sources.
An external data source is accessed through an embedded connection string, URL, or UNC path that you specified when you imported the original data into the workbook using the PowerPivot client application. Original connection information that is stored in the PowerPivot workbook is reused for subsequent data refresh operations. Although you can overwrite credentials used to connect to data sources, you cannot overwrite connection strings for data refresh purposes; only existing connection information is used.