American National Standard for voltage ratings

From www.ien.com
American National Standard For Electric Power Systems and Equipment -- Voltage Ratings
Rosslyn, VA, January 16, 2007 -- The National Electrical Manufacturers Association (NEMA) has published ANSI C84.1-2006, American National Standard for Electric Power Systems and Equipment -- Voltage Ratings (60 Hertz).
This standard establishes nominal voltage ratings and operating tolerances for 60 Hz 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. ANSI C84.1-2006 includes preferred voltage ratings up to and including 1200 kV maximum system voltage.
In defining maximum system voltage, voltage transients and temporary overvoltages caused by abnormal system conditions such as faults, loads, and rejection are excluded. However, voltage transients and temporary overvoltages may affect equipment operating performance and may be considered in the individual product standards.
The standard was expanded to cover voltages from 230-1,200 kV, and the requirements from the Institute of Electrical and Electronics Engineers, Inc (IEEE) 1312, which covered these higher voltages, were incorporated into the C84.1 revision.....