This standard establishes nominal voltage ratings and operating tolerances for 60-hertz electric power systems above 100 volts. It also makes recommendations to other standardizing groups with respect to voltage ratings for equipment used on power systems and for utilization devices connected to such systems. This standard includes preferred voltage ratings up to and including 1200 kV maximum system voltage@ as defined in the standard. In defining maximum system voltage@ voltage transients and temporary overvoltages caused by abnormal system conditions such as faults@ load rejection@ and the like are excluded. However@ voltage transients and temporary overvoltages may affect equipment operating performance and are considered in equipment application. Purpose The purposes of this standard are to: (1) Promote a better understanding of the voltages associated with power systems and utilization equipment to achieve overall practical and economical design and operation (2) Establish uniform nomenclature in the field of voltages (3) Promote standardization of nominal system voltages and ranges of voltage variations for operating systems (4) Promote standardization of equipment voltage ratings and tolerances (5) Promote coordination of relationships between system and equipment voltage ratings and tolerances (6) Provide a guide for future development and design of equipment to achieve the best possible conformance with the needs of the users (7) Provide a guide@ with respect to choice of voltages@ for new power system undertakings and for changes in older ones