What is the Definition of Low Voltage, Medium Voltage, High Voltage, and Extra High Voltage?

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Introduction
In electrical engineering, voltage classification is essential for the design, operation, and safety of electrical systems. Different voltage levels are used for various applications, from residential power distribution to industrial and transmission systems. The classification of voltage into low, medium, high, and extra high voltage helps standardize electrical systems and ensures appropriate safety measures are applied.

This article defines low voltage, medium voltage, high voltage, and extra high voltage according to common industry standards and international guidelines.

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1. Low Voltage (LV)

Definition: Low voltage refers to electrical systems operating at relatively low voltages, typically below 1,000 volts AC (alternating current) or 1,500 volts DC (direct current).

Range: 0 to 1,000 V AC or 0 to 1,500 V DC

Applications:

• Residential and commercial power distribution
• Lighting and small appliances
• Control systems and electronic devices
• Telecommunication systems

Standards: IEC 60364 and NEC (National Electrical Code) classify systems below 1,000 V AC as low voltage.

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2. Medium Voltage (MV)

Definition: Medium voltage refers to electrical systems operating between 1,000 volts and 35,000 volts AC. Medium voltage systems are commonly used for local power distribution and industrial applications.

Range: 1,000 V to 35,000 V AC

Applications:

• Industrial power distribution
• Local utility networks
• Large motor and equipment operation
• Renewable energy systems (e.g., wind and solar farms)

Standards: IEC 60038 and IEEE standards classify voltages in this range as medium voltage.

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3. High Voltage (HV)

Definition: High voltage refers to systems operating between 35,000 volts and 230,000 volts. High voltage is primarily used in long-distance power transmission and heavy industrial applications.

Range: 35,000 V to 230,000 V AC

Applications:

• Long-distance power transmission
• Heavy industrial facilities
• Power substations
• High-voltage testing laboratories

Standards: IEC 60071 and IEEE 1313.1 provide guidelines for high-voltage systems.

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4. Extra High Voltage (EHV)

Definition: Extra high voltage refers to systems operating above 230,000 volts. EHV is used for ultra-long-distance power transmission and large interconnection networks.

Range: Above 230,000 V AC

Applications:

• Ultra-long-distance transmission lines
• Interconnected power grids
• Bulk power transfer between regions

Standards: IEC 60071 and CIGRÉ guidelines are used for EHV systems.

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5. Summary of Voltage Classifications

Voltage Classification	Voltage Range	Common Applications
Low Voltage (LV)	0 to 1,000 V AC / 0 to 1,500 V DC	Residential, commercial, lighting, electronics
Medium Voltage (MV)	1,000 V to 35,000 V AC	Industrial distribution, local utilities, renewable energy
High Voltage (HV)	35,000 V to 230,000 V AC	Power transmission, substations, heavy industry
Extra High Voltage (EHV)	Above 230,000 V AC	Long-distance transmission, grid interconnection

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Conclusion
Understanding the classification of low, medium, high, and extra high voltage is essential for designing, operating, and maintaining electrical systems. Each voltage level serves specific purposes and requires appropriate safety measures and equipment. By adhering to international standards and guidelines, engineers and electricians can ensure the safe and efficient operation of electrical installations.

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References

• IEC 60038 - Standard Voltages
• IEC 60071 - Insulation Coordination
• IEEE 1313.1 - Standard for Insulation Coordination
• National Electrical Code (NEC) Handbook