The purpose of this standard is to describe the method of determining the maximum electrical voltage, referred to the unit of thickness, that a given material, to which a potential difference is applied under the indicated conditions, can withstand, without perforation. . A distinction is made between transverse or longitudinal dielectric strength, depending on whether the field is applied perpendicular or parallel to the surface of the solid. This standard refers only to the longitudinal dielectric strength of solid insulating materials, and to alternating voltages of normal frequencies (see standard UNE 20 039).