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Anonymous Poster

NEC / IEC Voltage Ranges

12/14/2009 6:03 AM

pls tell me the range of high, medium and low volatge according to NEC/IEC

if voltage less than 1000V, is it considered as low vaoltage?

and voltage greater than 1000V , is it considered as high Voltage?

what about medium voltage then?

pls i will be gratefull if any expert reply me
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PWSlack
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#1

Re: high,medium voltage

12/14/2009 6:10 AM

<...if voltage less than 1000V, is it considered as low voltage?...>

Yes, it is.

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JohnDG
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#2

Re: high,medium voltage

12/14/2009 6:18 AM

BS7671:2008 doesn't define "Medium Voltage". To paraphrase,

Extra-low: not more than 50Vac or 120V ripple-free dc (whether between conductors or to Earth).

Low: More than extra-low but not more than 1000Vac or 1500Vdc between conductors, or 600Vac or 900Vdc between conductor and Earth.

High: Normally more than low voltage.

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Anonymous Poster
#3

Re: high,medium voltage

12/14/2009 6:39 AM

NEC does not classify it.

As per IEEE Std. 141 (Red Book)
120-600V LV
2.4-34.5KV = MV
46KV-230KV = HV
345KV-1100KV= EHV

This is as per the version I have (a bit old at 1993, might have been revised quite a few times over)

As per IEC 60038

HV= 1KV

LV = 50V-1KV

ELV = <50V
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Anonymous Poster
#4
In reply to #3

Re: high,medium voltage

12/14/2009 6:41 AM

Corrigendum:

IEC: HV is >1KV
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JRaef
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#5
In reply to #3

Re: high,medium voltage

12/14/2009 1:40 PM

With the advent of 690V systems, I believe the IEEE std. was revised for LV being <1000V, MV being 1000-34.5kV.

But in N. America (NEC for the US and CEC for Canada), most LV equipment must now be "NRTL listed" (Nationally Recognized Testing Lab, i.e. UL or CSA), none of which recognize anything above 600V for LV systems.

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electricalexpert65
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#6

Re: NEC / IEC Voltage Ranges

12/15/2009 9:13 AM

India: As per the Indian Electricity Rules, 1956, vide Rule 2(av), the following are the limits:

Low Voltage: Not exceeding 250V

Medium Voltage: Not exceeding 650V

High Voltage: Not exceeding 33000V

Extra High Voltage: Exceeding 33000V

******

But, in IS 13234 – 1992, which is the "Guide for short-circuit current calculation in Three-phase A.C. Systems" – it is mentioned vide Table I that:

Low Voltage: 100V to 1000V

Medium Voltage: > 1kV to 35kV

High Voltage: > 35kV to 230kV

******

France: Vide a publication dated 14th November 1998, the French Regulations define three voltage levels as below:

Low Voltage: < 1kV

High Voltage A (HTA): > 1kV but </= 50kV

High Voltage B (HTB): > 50kV

******

CENELEC (The European Electrotechnical Standardisation Committee): Vide a publication dated 27th July 1992, the CENELEC recognises the following voltage levels:

Low Voltage: < 1kV

Medium Voltage: > 1kV but </= 35kV

High Voltage: > 35kV

******

IEC (International Electrotechnical Commission): In IEC 60071, the following ranges are defined:

Low Voltage: < 1kV

High Voltage Range I: > 1kV but </= 245kV

High Voltage Range II: > 245kV

The acronyms EHV (Extra High Voltage) and UHV (Ultra High Voltage), though are being used elaborately in India, have never been officially defined in any of the above three standards.

USA:

i) Vide IEEE Std. 241-1990 (IEEE Recommended Practice for Electric Power Systems in Commercial Buildings), Clause 3.1.1.2,

Low Voltage: A class of nominal system voltages 1000V or less

Medium Voltage: A class of nominal system voltages greater than 1000V and less than 100000V

High Voltage: A class of nominal system voltages equal to or greater than 100000V or less than 230000V

******

ii) Vide ANSI C84.1-1989 (Voltage ratings for electric power systems and equipment),

Low Voltage: 120V to 600V

Medium Voltage: 2400V to 69000V

High Voltage: 115000V to 230000V

******

iii) Vide ANSI C92.2-1987 (Power Systems – Alternating Current Electrical Systems and Equipment Operating at Voltages above 230kV Nominal – Preferred Voltage Ratings)

Extra High Voltage: 345000V to 785000V

Ultra High Voltage: 1100000V

******

Note: IEEE – Institution of Electrical and Electronic Engineers

ANSI – American National Standards Institute

******
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JRaef
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#7
In reply to #6

Re: NEC / IEC Voltage Ranges

12/15/2009 12:59 PM

Very definitive. GA.

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