Nominal medium and low
voltages are differ from one country to another, so let us know about nominal
voltage range of electrical distribution systems and outlines between low
voltage and medium voltage according to IEC standard:
In fact there is no
boundary between low and medium voltages but for economical reasons the medium
voltage rarely exceeds (35 k.v) and the low voltage rarely exceed (1000 v).
Medium Voltages 3-ph Systems:
According to (IEC 60038) standard the nominal medium voltages are divided according to thier values into two series:
Series No 1: nominal voltages are "3.3 k.v, 6.6 k.v, 11 k.v, 22k.v,
33 k.v ".
According to
IEC standard you should note that the highest and the lowest voltage shouldn't
differ due to operating condition by more than approximately ±10 % from the system
nominal voltage.
Series No 2: nominal voltages are "4.16 k.v, 12.47 k.v, 13.2
k.v, 13.8 k.v, 24.94 k.v, 34.5 k.v"
According to
IEC standard you should note that the highest and the lowest voltage shouldn't
differ due to operating condition by more than approximately ± 5 % from the
system nominal voltage.
Series no (1) is the
most prevalent and always IEC recommend that in one country the ratio between
to adjacent nominal values should be not less than "2" .
Low Voltages 3-ph Systems:
According to (IEC 60038) standard the nominal low voltages are divided
according to their frequency into two series:
50 HZ Series:
Nominal voltages are
"230/400 v, 400/690v, 1000v)
60 HZ Series:
Nominal voltages are "120/208v, 240v, 277/480v, 480v, 347/600v, 600 v"
IEC recommend that countries which have
existing nominal voltage system of 220/380 v and 240/415 v should evolve
towards the recommended value of 230/400 v at transition period shouldn't
exceed the year 2003 and the highest
and the lowest voltage shouldn't differ due to operating condition by more than
approximately ± 10 % from the system nominal voltage and then reduction to this
value "± 10 %" should be done.
Post a Comment