In electrical engineering, low voltage is a relative term, the definition varying by context. Different definitions are used in electric power transmission and distribution, compared with electronics design. Electrical safety codes define "low voltage" circuits that are exempt from the protection required at higher voltages. These definitions vary by country and specific codes or regulations.

IEC Definition

The International Electrotechnical Commission (IEC) standard IEC 61140:2016, concerning protection against electric shock, defines the low voltage (LV) band as ≤1000VACRMS or ≤1500VDC. This incorporates the Extra-low voltage band.

In electrical power systems low voltage most commonly refers to the mains voltagess as used by domestic and light industrial and commercial consumers. "Low voltage" in this context still presents a risk of electric shock, but only a minor risk of electric arcs through the air.

United Kingdom

British Standard BS 7671, Requirements for Electrical Installations. IET Wiring Regulations, defines supply system low voltage as:

The ripple-free direct current requirement only applies to 120VDC, not to any DC voltage above that. For example, a direct current that is exceeding 1500V during voltage fluctuations is not categorized as low-voltage.

United States

In electrical power , the US National Electrical Code (NEC), NFPA70, article725 (2005), defines low distribution system voltage (LDSV) as up to 49V.

The NFPA standard79 defines distribution protected extra-low voltage (PELV) as nominal voltage of 30Vrms or 60VDC ripple-free for dry locations, and 6Vrms or 15VDC in all other cases.

Standard NFPA 70E, Article 130, 2021 Edition, omits energized electrical conductors and circuit parts operating at less than 50 V from its safety requirements of work involving electrical hazards when an electrically safe work condition cannot be established.

UL standard508A, article43 (table43.1) defines 0to 20V peak/ 5A or 20.1to 42.4V peak/ 100VA as low-voltage limited energy (LVLE) circuits.

European Union

The low voltage directive (LVD) (2014/35/EU) defines low voltage for electrical equipment as devices operating within the range between 50 V AC to 1000 V AC or 75 V DC to 1500 V DC. These ratings are for the inputs and outputs of the device, not internal voltages.

Australia

Safe Work Australia and Energy Networks Australia defines low voltage as a nominal voltage between 50 V AC and 1000 V AC or a ripple free DC voltage between 120V DC and 1500 V DC. Anything below the minimum values of the low voltage range is considered extra low voltage.

South Africa

In "Electricity Supply By-law, 2023" low voltage is defined as nominal voltage levels less than 1000 V AC or 1500 V DC that are used for distribution.

Canada

The Canadian Electrical Code defines low voltage as ranging from 31 V to 750 V.

See also

• High voltage

• Low Voltage Directive

References

Further reading

• Defining Low Voltage Circuits