Gives insulation requirements for power transformers and the corresponding insulation tests for specific windings. Applies to single-phase and three-phase oil-immersed power transformers as defined in the IEC 60076-1. It Includes appendices on: partial discharge measurements during induced a.c. withstand voltage test on transformers; overvoltage transferred from a high-voltage winding to a low-voltage winding; information to be supplied with enquiries and orders. The contents of the corrigendum of December 2000 have been included in this copy.