Voltage classification

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
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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
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France: Vide a publication dated 14th November 1998, the French Regulations define three voltage levels as below:
Low Voltage: <> 1kV but 50kV
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CENELEC (The European Electrotechnical Standardisation Committee): Vide a publication dated 27th July 1992, the CENELEC recognises the following voltage levels:
Low Voltage: <> 1kV but 35kV
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IEC (International Electrotechnical Commission): In IEC 60071, the following ranges are defined:
Low Voltage: <> 1kV but 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
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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
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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
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Note: IEEE – Institution of Electrical and Electronic Engineers
ANSI – American National Standards Institute