IEC 62631-2-1:2018 describes test methods for the determination of permittivity and dissipation factor properties of solid insulating materials (AC methods from 0,1 Hz up to 10 MHz). This first edition cancels and replaces the first edition IEC 60250, published in 1969. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition: a. technical frequencies confined to AC methods; b. update on measurements on solid dielectric materials.