Applies to post insulators and post insulator units of ceramic material or glass for indoor and outdoor service 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.Notes:- May also be regarded as a provisional standard for insulators for use on d.c. systems, see IEC 438.- When considering hollow insulators, see IEC 233.- Tests on indoor post insulators of organic material will be covered by a future publication: Tests on indoor post insulators of organic material for systems with nominal voltages greater than 1 000 V up to but not including 300 kV.- For artificial pollution and radio-interference tests, see IEC 437 and 507.- For numerical values for insulator characteristics and for selection of insulators for specific operating conditions, see IEC 273.