標準號：IS 7421-1988
發布日期：1989/8/1 12:00:00
實施日期：1999/12/31 12:00:00
適用范圍：1.1 This standard covers the requirements, characteristics and methods of tests for porcelain bushings for indoor and outdoor use, suitable for electrical equipment of nominal system voltages up to and including 1 000 V and frequency between 15 and 60 Hz.1.2 This standard also applies to bushings supplied separately for use in the construction of electrical apparatus, transformers, electrical installations and to bushings supplied as an integral part of equipment when required by the relevant equipment specifications.1.3 This standard does not apply to bushings for use with rectifiers, rotating machines, testing transformers, dc converter transformers or to terminals for power cables ( pot heads ). Suchbushings, if not covered by relevant Indian Standard, shall be subjected to special agreement between the purchaser and the supplier.