EE-1 Course: Voltage Ranges - Part Two



as we show in the previous topic that There are (6) ranges of voltages used in electrical world as follows:
  1. Extra low voltage range
  2. Low voltage range
  3. Medium voltage range
  4. High voltage range
  5. Extra high voltage range
  6. Ultra high voltage range


 and now, we will know the voltage limits for each range of them in different standards and codes as follows:



Extra Low voltage range (elv)


Standard/Code
AC
DC
IEC (between conductor and earth)
0 -49 Volts
0 – 119 Volts
NEC
0 – 49 Volts
BS
0 – 49 Volts
0 – 119 Volts




Low voltage range (lv)


Standard/Code
AC
DC
IEC (between conductor and earth)
50 – 1000 Volts
120 – 1500 Volts
BS (between conductor and earth)
50–600 Volts
120–900 Volts
BS (between conductors)
50- 1000 Volts
120–1500 Volts
NEC
50-600 Volts




Medium voltage range (mv)


Standard/Code
AC
DC
IEC /IEEE

1000 – 35 ,000 Volts
1500 V – 50 KV
ANSI
1000 – 35 ,000 Volts

NECA/NEMA

600 – 69 ,000 Volts
BS (between conductors)

1000 – 11,000 Volts
NEC
MV Range not defined by NEC




High Voltage Range (hv)


Standard/Code
AC
DC
IEC /IEEE (between conductor and earth)
35,000 – 230,000 Volts
50 KV – 500 KV
BS (between conductors)
11,000 – 66,000 Volts

NEC
>  600 Volts




Extra High Voltage Range (ehv)


Standard/Code
AC
DC
IEC /IEEE  (between conductor and earth)
230,000 – 800,000 Volts
> 500 KV
BS (between conductors)
≥ 66,000 Volts

NEC
EHV Range not defined by NEC




Ultra high voltage range (uhv)


Standard/Code
AC
DC
IEC /IEEE  (between conductor and earth)
1000 – 1200 KV
500- 800 KV



also, it is important to know the following three definitions which are :



System voltage 

the voltage bounded by the step-up and step-down transformer voltage, e.g., 240 volts, 480 volts, and 600 volts.

Utilization voltage 

the voltage at the terminals of the equipment, e.g., 230 volts, 460 volts, and 575 volts.

Service voltage

the voltage at the utility, or source supply, boundary.


Note



1- The difference between service and utilization voltage allows for voltage drop in facility wiring between the point of utility delivery and the utilization equipment. The National Electrical Code (NEC), recommends that voltage drop in branch circuits (sub panel to utilization equipment) be less than three percent. It also recommends that feeder (between main panel and subpanel) voltage drop be less than three percent, with the combined voltage drop of branch plus feeder being less than five percent.

For example, a nominal 208 V supply system will be connected to motors with "200 V" on their nameplates. This allows for the voltage drop between equipment and supply.

2- The following system voltages are the used ones around the world as follows:


For more information about 
Electrical System Configurations press on the link. 

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