This International Standard IEC 60168 is applicable to post insulators and post insulator units of ceramic material or glass, for indoor and outdoor use in electrical installations or equipment, operating on alternating current with a nominal voltage greater than 1 000 V and a frequency not greater than 100 Hz. This standard may be regarded as a provisional standard for post insulators for use on d.c. systems. IEC 60438 gives general guidance for those insulators. This standard does not apply to composite insulators, or to those indoor post insulators in organic material which are covered by another IEC standard [1]*. The object of this standard is to define: – the terms used; – the electrical and mechanical characteristics of post insulators; – the conditions under which the specified values of these characteristics are verified; – the methods of test; – the acceptance criteria. Numerical values of characteristics of post insulators are specified in IEC 60273. This standard does not include requirements dealing with the choice of post insulators for specific operating conditions. NOTE 1 A guide for the choice of insulators under polluted conditions is available, see [2]. NOTE 2 This standard does not include radio interference tests or artificial pollution tests. These subjects and relevant test methods are dealt with in other IEC publications, see [3], [4] and [5]. NOTE 3 When this standard is applied to hollow post insulators, other IEC publications should also be taken into account, see [6] and [7].