Electric wires - what that colour means?
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.
Wires, electricity and safety issues
Wiring 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.
Standards and regulation - electrical wiring
An electrical code is a set of regulations for electrical wiring. The intention of an electrical code is to provide standards to ensure electrical wiring systems that are safe and unlikely to produce either electric shock or fires. Ways in which electrical codes ensure safety include ways to prevent (or mitigate) short circuits, ground faults, and overheating from inadequate current-carrying capacity (ampacity). Appropriately rated fuses or circuit breakers are used to interrupt a circuit loop whose ampacity is exceeded to avoid overheating of wires or other fixtures. Electrical codes are usually devised by national or international technical organizations, and adopted as law to make them enforceable. Electrical codes differ based on geographic area. See the following:
DIN VDE (German Institute for Standardization) published by DIN-Norms is used in Germany
National Electrical Code has been adopted for electrical wiring in the United States and for Mexico, Costa Rica, Venezuela and Colombia
IEC 60364 is used as a basis for electrical codes in many European countries
Canadian Electrical Code published by the CSA is used in Canada (see Electrical wiring in North America).
British Standard BS 7671 is the set of regulations for electrical wiring in the United Kingdom.
Australian/New Zealand Standard AS/NZS 3000:2007 Wiring Rules is used in Australia and New Zealand.
NF C 15-100 (fr) is used for low voltage installations in France
RGIE (fr) (Réglement Général sur les Installations Électriques) is used for installations in Belgium.
AREI (nl) (Algemeen Reglement Elektrische Installaties) is used for installations in Flanders, Belgium.