This standard is applicable to bushings, as defined in Section Two, which are supplied separately, intended for use in electrical apparatus, transformers, and installations, for three-phase alternating current systems, having rated voltages above 1 000 V and frequencies between 15 Hz and 60 Hz. This standard is not applicable to bushings for use with rectifiers, rotating machines, testing transformers, or to terminals for power cables (potheads). Such bushings shall be subject to special agreement between supplier and purchaser.Moreover this standard is not applicable to insulating structures similar to bushings, which are used as support insulators inside metal-enclosed switchgear according to IEC Publication 517: High-voltage Metal-enclosed Switchgear for Rated Voltages of 72.5 kV and Above.Notes 1. - The application of this standard to bushings for other than three-phase systems should be subject to special agreement between supplier and purchaser.2. - If a bushing, due to its design or use, cannot be tested separately under the conditions specified in this standard, the test procedure should be subject to special agreement between supplier and purchaser.