(Please let me add that you can get the pdf of the Iec 60894 from the official website of Iec or through other online sources which provide free or paid pdf of iec standards.)
While you can find free summaries and tutorials (like this article), the official standard is the only source for the exact circuit diagrams, calibration routines, and voltage step increments. If you are performing acceptance testing on new coils or assessing old generators for refurbishment, purchasing the genuine from the IEC Webstore is an investment in safety and reliability. iec 60894 pdf
A: No. Tan δ requires measuring phase angle differences in microamps. You need a specialized tan delta bridge or an automatic insulation analyzer (e.g., Megger IDAX, Doble M4100). (Please let me add that you can get