60hz electric power systems and equipment - voltage ratings 60 hertz 电力系统和设备.电压额定值
2.
Preferred voltage ratings for alternating - current electrical systems and equipment operating at voltages above 230 kv nominal 公称电压超过230kv的交流电气系统和设备用优选电压额定值
3.
Power systems - preferred voltage ratings for alternating - current electrical systems and equipment operating at voltages above 230 kv nominal 电力系统.标称工作电压在230千伏以上的交流电力系统和设备用优选电压额定值