Wikipedia about wires and cables
Building wiring is the electrical wiring and associated devices such as switches, meters and light fittings used in buildings or other structures. Electrical wiring uses insulated conductors.
Wires and cables are rated by the circuit voltage, temperature and environmental conditions (moisture, sunlight, oil, chemicals) in which they can be used, and their maximum current. Wiring safety codes vary by country, and the International Electrotechnical Commission (IEC) is attempting to standardise wiring amongst member countries. Colour codes are used to distinguish line, neutral and earth (ground) wires.
Is it worth it to hire an electrician?
Although many people think that minor electrical repairs do not require the employment of a specialist such as a qualified electrician, the majority of jobs decides to offer a permanent job for an electrician. Why is this happening? Well, according to the law serious fault electrical installations may only be carried out by specialists. It is a profession of high risk and therefore must have the expertise to carry it out. In the absence of skills and knowledge of repair system can lead to severe injury or even a real tragedy.
Industrial classification of electricians - by Wikipedia
Electrical contractors are generally classified by three major types of work performed.
"Outside" or "line" contractors are responsible for high-voltage power transmission and distribution lines. Line contractors build and maintain the infrastructure required to transport electricity generated at a power plant through a series of high-voltage lines and substations before it is used to power facilities, buildings, and homes.
"Inside" electrical contractors provide electricity to any structure within a property?s boundary lines, including outdoor lighting or substations. Under current construction specification guidelines, "inside" electrical contractors can serve as prime contractors for all electrical and cabling design, installation, and maintenance for commercial, institutional, and residential buildings. Projects also include Database Centers/Infrastructure and Pharmaceutical Work.
"Integrated building systems" (IBS) or "Voice/Data/Video" (VDV) electrical contractors work primarily with low-voltage installations such as back-up power, climate controls, wireless networks, energy-efficient lighting, telecommunications, fiber optics, and security systems. IBS contractors are particularly skilled at integrating these system controls to work together for maximum energy efficiency and building performance.