This part of IEC 62332, which is a technical specification, is applicable to EIS containing solid and liquid components where the thermal stress is the dominant ageing factor, without restriction to voltage class.

This part specifies a sealed tube test procedure for the thermal evaluation and qualification of electrical insulation systems (EIS). One aspect of this procedure is to also provide a method to assign thermal classifications to materials used in EIS where solid and liquid components are both used. This procedure describes a comparative ageing method whereby a reference system composed of kraft paper and mineral oil is compared to a candidate system of any combination of solid and insulating liquid. The test procedures in this part are specifically applicable to liquid immersed transformer insulation systems.

Similar procedures should also work for other electrotechnical devices with a combination of liquid and solid components, such as bushings, cables or capacitors, but this will be added as additional parts once experience is gained using this technical specification.