scope:

The standard applies to equipment for three-phase a.c. systems, with a highest voltage for equipment above 1 kV. It does not apply to equipment on which the different phases are separated by metal barriers. The object of this standard is the specification of phase-to-phase insulation of the equipment used in electric power systems. Each apparatus committee is responsible for specifying the insulation level and test procedures suitable for its equipment, recognizing the recommendations given in this standard. For the tests prescribed in this standard, the values of the rated withstand voltages shall be chosen from the standardized insulation levels specifed in this standard.