Even internal use without a license is copyright infringement. The IEC actively scans torrent sites and forums, issuing takedowns and tracking downloads. Your IT department may block your access.
The search for is a journey down a dangerous, illegal, and ultimately unprofessional path. The correct standard is almost certainly IEC 60071 (Insulation co-ordination), and the only safe version is the official PDF purchased from the IEC Webstore or an authorized reseller. iec 600771 pdf repack
If you are looking for a feature-dense version of the file, the official IEC 60077-1:2017 RLV is the gold standard. It provides a side-by-side, redline-tracked comparison showing exactly what text changed, was deleted, or was added between the 1999 and 2017 editions. Even internal use without a license is copyright