To enable wires to be easily and safely identified, all common wiring safety codes mandate a colour scheme for the insulation on power conductors.
In a typical electrical code, some colour-coding is mandatory, while some may be optional.Many local rules and exceptions exist per country, state or region.Older installations vary in colour codes, and colours may fade with insulation exposure to heat, light and ageing. As of March 2011, the European Committee for Electrotechnical Standardization (CENELEC) requires the use of green/yellow colour cables as protective conductors, blue as neutral conductors and brown as single-phase conductors.The United States National Electrical Code requires a green or green/yellow protective conductor, a white or grey neutral, and a black single phase. The United Kingdom requires the use of wire covered with green insulation, to be marked with a prominent yellow stripe, for safe earthing (grounding) connections.This growing international standard was adopted for its distinctive appearance, to reduce the likelihood of dangerous confusion of safety earthing (grounding) wires with other electrical functions, especially by persons affected by red-green colour blindness. In the UK, phases could be identified as being live by using coloured indicator lights: red, yellow and blue.The new cable colours of brown, black and grey do not lend themselves to coloured indicators.For this reason, three-phase control panels will often use indicator lights of the old colours.Źródło: https://en.wikipedia.org/wiki/Electrical_wiring
Wiring safety codes - WikipediaWiring safety codes are intended to protect people and property from electrical shock and fire hazards.Regulations may be established by city, county, provincial/state or national legislation, usually by adopting a model code (with or without local amendments) produced by a technical standards-setting organisation, or by a national standard electrical code. Electrical codes arose in the 1880s with the commercial introduction of electrical power.Many conflicting standards existed for the selection of wire sizes and other design rules for electrical installations. The first electrical codes in the United States originated in New York in 1881 to regulate installations of electric lighting. Since 1897 the US National Fire Protection Association, a private non-profit association formed by insurance companies, has published the National Electrical Code (NEC).States, counties or cities often include the NEC in their local building codes by reference along with local differences.
The NEC is modified every three years.It is a consensus code considering suggestions from interested parties. The proposals are studied by committees of engineers, tradesmen, manufacturer representatives, fire fighters and other invitees.Źródło: https://en.wikipedia.org/wiki/Electrical_wiring
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