What are the IEC Voltage Classifications

The International Electrotechnical Commission (IEC) has established a standard system for classifying voltages used in electrical power transmission and distribution. This system, known as the IEC voltage classifications, ensures that different voltages are consistently designated and helps to ensure the safety and compatibility of electrical equipment.

Low Voltage Classifications

The IEC defines low voltage as any voltage up to 1000 volts alternating current (VAC) or 1500 volts direct current (VDC). Within the low voltage classification, there are several specific categories:

Extra Low Voltage (ELV): ELV refers to voltages not exceeding 50 VAC or 120 VDC. ELV systems are often used for low-power electronic devices and do not pose significant electric shock hazards.

Low Voltage (LV): LV refers to voltages between ELV and 1000 VAC or 1500 VDC. It is the most common voltage category used in residential, commercial, and industrial settings.

High Safety Extra Low Voltage (SELV): SELV refers to voltages not exceeding 50 VAC or 120 VDC but with additional safety measures to prevent electric shock. SELV systems are typically used in wet or hazardous environments.

Medium Voltage Classifications

The IEC defines medium voltage as any voltage greater than 1000 VAC or 1500 VDC, but not exceeding 35,000 VAC or 45,000 VDC. The following classifications fall under the medium voltage category:

Medium Voltage (MV): MV refers to voltages between 1000 VAC or 1500 VDC and 35,000 VAC or 45,000 VDC. It is commonly used for power distribution in industrial and commercial applications.

High Voltage (HV): HV refers to voltages exceeding 35,000 VAC or 45,000 VDC, but not exceeding 230,000 VAC or 320,000 VDC. HV systems are typically used for long-distance transmission of electric power.

High Voltage Classifications

The highest voltage classification according to the IEC is Extra High Voltage (EHV). EHV refers to voltages exceeding 230,000 VAC or 320,000 VDC. EHV systems are primarily used for extremely long-distance transmission of electric power or in special applications where high levels of insulation and safety measures are required.

In conclusion, the IEC voltage classifications provide a standardized system for categorizing voltages in electrical power systems. By following these classifications, manufacturers and electrical professionals can ensure the safety and compatibility of electrical equipment across different voltage ranges.