Low voltage
Encyclopedia
Low voltage when used as an electrical engineering term concerning an electricity supply grid or industrial use, broadly identifies safety considerations of the system based on the voltage used. The meaning of the term "low voltage" is somewhat different when used with regard to a more typical end user's distribution system, which see below. With regard to an electricity supply system, 'low voltage' most commonly refers to "mains voltage". "Low voltage" in this context is characterized by carrying a substantial risk of electric shock, but only a minor risk of electric arcs through air. Also in this context, "Low voltage" is distinguished from:
Extra low voltage (supply system) – which carries a much reduced risk of electric shock
High voltage (supply system) – where electrical arcing is a substantial additional risk.
Some other commonly used definitions include:
The International Electrotechnical Commission (IEC) defines low voltage as any voltage in the range 50–1000 V AC or 120–1500 V DC.
Article 490.2 of the United States 2005 National Electrical Code only defines "high voltage" as more than 600 volts. Nevertheless the NFPA 79 article 6.4.1.1 defines PELV as nominal voltage of 30 Vrms or 60 Vdc ripple free for dry locations and 6 Vrms or 15 Vdc in all other cases. UL 508A article 43.1.2 is more stringent and uses those values as maximum the same way as NEC 2008.
Within the context of the "distribution system" the United States 2005 National Electrical Code (NEC) defines low (distribution system) voltage as 0 - 49 volts . . Low Distribution (system voltage) is covered by 250.20(A) of this code.
British Standard BS 7671:2008 defines low voltage as
50–1000 V AC or 120–1500 V ripple-free DC between conductors;
50–600 V AC or 120–900 V ripple-free DC between conductors and Earth.
Low voltage when used as an electrical engineering term concerning an electricity supply grid or industrial use, broadly identifies safety considerations of the system based on the voltage used. The meaning of the term "low voltage" is somewhat different when used with regard to a more typical end user's distribution system, which see below. With regard to an electricity supply system, 'low voltage' most commonly refers to "mains voltage". "Low voltage" in this context is characterized by carrying a substantial risk of electric shock, but only a minor risk of electric arcs through air. Also in this context, "Low voltage" is distinguished from:
Some other commonly used definitions include:
Extra low voltage (supply system) – which carries a much reduced risk of electric shock
High voltage (supply system) – where electrical arcing is a substantial additional risk.
Some other commonly used definitions include:
The International Electrotechnical Commission (IEC) defines low voltage as any voltage in the range 50–1000 V AC or 120–1500 V DC.
Article 490.2 of the United States 2005 National Electrical Code only defines "high voltage" as more than 600 volts. Nevertheless the NFPA 79 article 6.4.1.1 defines PELV as nominal voltage of 30 Vrms or 60 Vdc ripple free for dry locations and 6 Vrms or 15 Vdc in all other cases. UL 508A article 43.1.2 is more stringent and uses those values as maximum the same way as NEC 2008.
Within the context of the "distribution system" the United States 2005 National Electrical Code (NEC) defines low (distribution system) voltage as 0 - 49 volts . . Low Distribution (system voltage) is covered by 250.20(A) of this code.
British Standard BS 7671:2008 defines low voltage as
50–1000 V AC or 120–1500 V ripple-free DC between conductors;
50–600 V AC or 120–900 V ripple-free DC between conductors and Earth.
Low voltage when used as an electrical engineering term concerning an electricity supply grid or industrial use, broadly identifies safety considerations of the system based on the voltage used. The meaning of the term "low voltage" is somewhat different when used with regard to a more typical end user's distribution system, which see below. With regard to an electricity supply system, 'low voltage' most commonly refers to "mains voltage". "Low voltage" in this context is characterized by carrying a substantial risk of electric shock, but only a minor risk of electric arcs through air. Also in this context, "Low voltage" is distinguished from:
- Extra low voltage (supply system)Extra low voltageIn electricity supply, the use of extra-low voltage is one of several means to protect against electrical shock. The International Electrotechnical Commission and its member organizations define an ELV circuit as one in which the electrical potential of any conductor against earth is not more...
– which carries a much reduced risk of electric shock - High voltage (supply system)High voltageThe term high voltage characterizes electrical circuits in which the voltage used is the cause of particular safety concerns and insulation requirements...
– where electrical arcing is a substantial additional risk.
Some other commonly used definitions include:
- The International Electrotechnical CommissionInternational Electrotechnical CommissionThe International Electrotechnical Commission is a non-profit, non-governmental international standards organization that prepares and publishes International Standards for all electrical, electronic and related technologies – collectively known as "electrotechnology"...
(IEC) defines low voltage as any voltage in the range 50–1000 V ACAlternating currentIn alternating current the movement of electric charge periodically reverses direction. In direct current , the flow of electric charge is only in one direction....
or 120–1500 V DCDirect currentDirect current is the unidirectional flow of electric charge. Direct current is produced by such sources as batteries, thermocouples, solar cells, and commutator-type electric machines of the dynamo type. Direct current may flow in a conductor such as a wire, but can also flow through...
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- Article 490.2 of the United States 2005 National Electrical Code only defines "high voltage" as more than 600 volts. Nevertheless the NFPA 79 article 6.4.1.1 defines PELV as nominal voltage of 30 Vrms or 60 Vdc ripple free for dry locations and 6 Vrms or 15 Vdc in all other cases. UL 508A article 43.1.2 is more stringent and uses those values as maximum the same way as NEC 2008.
- Within the context of the "distribution system" the United States 2005 National Electrical Code (NEC) defines low (distribution system) voltage as 0 - 49 volts . . Low Distribution (system voltage) is covered by 250.20(A) of this code.
- British Standard BS 7671BS 7671British Standard BS 7671 "Requirements for electrical installations" is the national standard in the United Kingdom for low voltage electrical installations....
:2008 defines low voltage as- 50–1000 V AC or 120–1500 V ripple-free DC between conductors;
- 50–600 V AC or 120–900 V ripple-free DC between conductors and Earth.