I created a excelfile with around 50 worksheets. All information is in the summary in the first worksheet, but for detailed information people can check the source in the worksheet.
I thought it would be nice to have an internal link to the worksheet (people want to know why the sales were down in July 2016 worksheet etc). 
But while I seem to be able to create hyperlinks to websites, I just want to make it work in this excel file.
Is this possible at all?
Actually, you can add local hyperlinks but have to control the location. The specification says this of the location attribute: 

Location within target. If target is a workbook (or this workbook)
  this shall refer to a sheet and cell or a defined name. Can also be an
  HTML anchor if target is HTML file.

I think this works by setting target to None and ref to the cell reference.
Create internal links within excelsheet with openpyxl