Explore the classification of voltage levels as per Indian and international standards, including LV, MV, HV, and EHV. Understand the standard voltage in India, voltage range in India, and key regulations on voltage levels.
In the field of electrical engineering, professionals frequently encounter terms like LV, MV, HV, and EHV. These refer to voltage classifications that help standardize design, safety, and equipment usage. However, the exact definitions and voltage ranges can vary across different national and international standards. This article focuses on the voltage standard in India, its evolution, and how it compares with global practices.
What are Voltage Levels?
Voltage levels are classifications based on the amount of electrical potential difference (voltage) in a system. They help determine the types of insulation, protection, and equipment needed. These are generally grouped into:
- Low Voltage (LV)
- Medium Voltage (MV)
- High Voltage (HV)
- Extra High Voltage (EHV)
Each of these classifications plays a crucial role in power generation, transmission, and distribution systems.
Voltage Standards in India
India’s voltage classification was originally defined under the Indian Electricity Rules, 1956, which specified:
- Low Voltage (LV): Not exceeding 250 V
- Medium Voltage (MV): Between 250 V and 650 V
- High Voltage (HV): Above 650 V and up to 33,000 V
- Extra High Voltage (EHV): Above 33,000 V
However, these definitions were removed in the Central Electricity Authority (CEA) Regulations, 2010, which currently do not define specific voltage ranges. Nevertheless, the National Electrical Code (NEC) of India, 2011 (Reaffirmed in 2016) offers updated voltage classifications:
- LV Voltage Range: ≤ 250 V
- MV Voltage Range: > 250 V and ≤ 650 V
- HV Voltage Range: > 650 V and < 33 kV
- EHV Voltage Range: ≥ 33 kV
Voltage Classification in International Standards
Different countries and international bodies define types of voltage and voltage ranges differently. Here’s how they compare:
IEC Standards (International Electrotechnical Commission)
- Low Voltage (LV): < 1 kV
- High Voltage (HV) Range I: 1 kV < Um ≤ 245 kV
- High Voltage (HV) Range II: Um > 245 kV
ANSI/IEEE (USA)
- Low Voltage: 120 V to 600 V
- Medium Voltage: 2.4 kV to 69 kV
- High Voltage: 115 kV to 230 kV
- Extra High Voltage: 345 kV to 765 kV
- Ultra High Voltage: > 1100 kV
CENELEC (The European Electrotechnical Standardization Committee)
As per a publication dated 27th July 1992, CENELEC (The European Committee for Electrotechnical Standardization) defines the following voltage levels:
- Low Voltage: < 1 kV
- Medium Voltage: 1 kV to 35 kV
- High Voltage: > 35 kV
French Standards
As per the French Regulations published on 14th November 1998, three voltage levels are defined as follows:
- Low Voltage (BT): < 1 kV
- High Voltage A (HTA): 1 kV to 50 kV
- High Voltage B (HTB): > 50 kV
Table: Voltage Classifications as Defined by Various International Standards and Regulations
The table below presents a comparative overview of how various global standards—including those from IEC, IEEE, ANSI, CENELEC, and national regulations—define and categorize voltage levels.
| Standard / Regulation | Voltage Category | Voltage Range |
|---|---|---|
| IS/IEC 60071-1 & IEC 60071-1 Insulation Coordination – Definitions, principles, and rules | Low Voltage | Um < 1 kV |
| High Voltage – Range I | 1 kV < Um ≤ 245 kV | |
| High Voltage – Range II | Um > 245 kV | |
| IS 13234 / IEC 60909 Short-circuit currents in three-phase AC systems | Low Voltage | 100 V to 1000 V |
| Medium Voltage | > 1 kV to 35 kV | |
| High Voltage | > 35 kV to 230 kV | |
| ANSI C84.1-1989 Electric Power Systems and Equipment – Voltage Ratings (60 Hz) | Low Voltage | 120 V to 600 V |
| Medium Voltage | 2.4 kV to 69 kV | |
| High Voltage | 115 kV to 230 kV | |
| ANSI C92.2-1987 / IEEE C92.2-1987 For voltages above 230 kV | Extra High Voltage | 345 kV to 765 kV |
| Ultra High Voltage | 1100 kV & above | |
| IEEE 141-1993 (Red Book) IEEE 241-1990 (Grey Book) | Low Voltage | 120 V to 600 V |
| Medium Voltage | 2.4 kV to 34.5 kV | |
| High Voltage | 46 kV to 230 kV | |
| Extra High Voltage | 345 kV to 1100 kV | |
| IEEE 1623-2020 Functional Specification for Medium Voltage Electronic Shunt Devices | Medium Voltage | 1 kV to 35 kV |
| NECA/NEMA 600-2003 Installing and Maintaining Medium-Voltage Cable | Medium Voltage | 600 V to 69 kV |
| French Standard (14 Nov 1998) | Low Voltage | < 1 kV |
| High Voltage A (HTA) | > 1 kV to ≤ 50 kV | |
| High Voltage B (HTB) | > 50 kV | |
| CENELEC (27 July 1992) | Low Voltage | < 1 kV |
| Medium Voltage | > 1 kV to ≤ 35 kV | |
| High Voltage | > 35 kV | |
| IEC 62271-1 High-voltage switchgear and controlgear | High Voltage | > 1,000 V (general use) |
| Medium Voltage (common use) | 1 kV to 52 kV |
India Voltage Range in Practice
Although exact voltage classifications are no longer defined in current Indian regulations, in practical terms, the following India voltage range is commonly used:
| Voltage Type | Voltage Range |
|---|---|
| Low Voltage (LV) | Up to 250 V |
| Medium Voltage (MV) | 250 V to 650 V |
| High Voltage (HV) | 650 V to 33 kV |
| Extra High Voltage (EHV) | Above 33 kV |
This practical classification aligns well with legacy rules and the NEC 2011. It is widely followed in utilities, electrical design, and safety standards across India.
The IEC 60038 Misconception
Many professionals wrongly assume that IEC 60038 provides a clear classification of voltage levels. In truth, IEC 60038 only lists standard voltages without explicitly categorizing them into LV, MV, HV, or EHV. For example:
- Table 1: Nominal voltages from 100 V to 1,000 V
- Table 2 – DC and AC traction systems
- Table 3: Nominal voltages above 1 kV and up to 35 kV
- Table 4: Voltages from 35 kV to 230 kV
- Table 5: Equipment rated above 245 kV
- Table 6 – Equipment having a nominal voltage below 120 V AC or below 750 V DC.
In reality, throughout the entire IEC 60038 standard, terms such as Medium Voltage, High Voltage, or Extra High Voltage are not mentioned. The term “Low Voltage” appears only once, as a footnote to Table 1 in Section 2, merely indicating voltage variation limits. Therefore, it is misleading to claim that IEC 60038 provides a formal classification of LV, MV, HV, or EHV voltage levels.
Conclusion
As evident, there is no universal definition of voltage levels, and classifications vary across national and international standards. The standard voltage in India has evolved over time, with the current NEC 2011 providing practical guidelines. However, discrepancies still exist globally, and there’s a pressing need for harmonized voltage classification.
Until then, electrical professionals must remain aware of the context—whether dealing with voltage in India or abroad—to apply the correct voltage ranges in design, installation, and safety.
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