Low voltage
Low amounts of electrical volts
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.
01IEC Definition
| IEC 61140 voltage bands | AC RMS | DC | Defining risk |
|---|---|---|---|
| High voltage | > 1,000 | > 1,500 | Electrical arcing |
| Low voltage | ≤ 1,000 | ≤ 1,500 | Electrical shock |
| Extra-low voltage | < 50 | < 120 | Electrical fire |
The International Electrotechnical Commission (IEC) standard IEC 61140:2016, concerning protection against electric shock, defines the low voltage (LV) band as ≤ 1000 V AC RMS or ≤ 1500 V DC. This incorporates the Extra-low voltage band.
In electrical power systems low voltage most commonly refers to the mains voltages 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.
02United Kingdom
British Standard BS 7671, Requirements for Electrical Installations. IET Wiring Regulations, defines supply system low voltage as:
exceeding 50 V AC or 120 V ripple-free DC. but not exceeding 1000 V AC or 1500 V DC between conductors, or 600 V AC or 900 V DC between conductors and earth.
The ripple-free direct current requirement only applies to 120 V DC, not to any DC voltage above that. For example, a direct current that is exceeding 1500 V during voltage fluctuations is not categorized as low-voltage.
03United States
In electrical power distribution, the US National Electrical Code (NEC), NFPA 70, article 725 (2005), defines low distribution system voltage (LDSV) as up to 49 V.
The NFPA standard 79 article 6.4.1.1 defines distribution protected extra-low voltage (PELV) as nominal voltage of 30 Vrms or 60 V DC ripple-free for dry locations, and 6 Vrms or 15 V DC 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 standard 508A, article 43 (table 43.1) defines 0 to 20 V peak / 5 A or 20.1 to 42.4 V peak / 100 VA as low-voltage limited energy (LVLE) circuits.
04European 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.
05Australia
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.
06South 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.
07Canada
The Canadian Electrical Code defines low voltage as ranging from 31 V to 750 V.
Sources and credits
This article is adapted from the Wikipedia article “Low voltage”, written by its contributors and licensed under CC BY-SA 4.0. Fathomly has changed the layout, removed citation markers, navigation and maintenance notices, and adjusted punctuation. This adapted version is shared under the same license. For references, see the original article.
Images, from Wikimedia Commons:
- Uk 13a double socket.jpg by Ianinhoose at English Wikipedia, Public domain
- European plug and sockets, UE standard, EU plug and socket wiring diagram, schuko, french socket, cee 7-7.jpg by Electro-world-standard, CC BY-SA 4.0
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