Specifies a general test procedure for the thermal evaluation and qualification of electrical insulation systems (EIS) and establishes a procedure that compares the performance of a candidate EIS to that of a reference EIS.This basic standard is applicable to existing or proposed EIS used in electrotechnical products with an input voltage of up to 1 000 V where the thermal factor is the dominating ageing factor.This second edition cancels and replaces the first edition published in 1998, and constitutes a technical revision to make this basic standard compatible with parts 21 and 22.