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History of electric system
By 1890 the electric power industry was flourishing, and power companies had built thousands of power systems (both direct and alternating current) in the United States and Europe. These networks were effectively dedicated to providing electric lighting. During this time a fierce rivalry known as the "War of Currents" emerged between Thomas Edison and George Westinghouse over which form of transmission (direct or alternating current) was superior.8 In 1891, Westinghouse installed the first major power system that was designed to drive a 100 horsepower (75 kW) synchronous electric motor, not just provide electric lighting, at Telluride, Colorado.9 On the other side of the Atlantic, Mikhail Dolivo-Dobrovolsky built a 20 kV 176 km three-phase transmission line from Lauffen am Neckar to Frankfurt am Main for the Electrical Engineering Exhibition in Frankfurt.10 In 1895, after a protracted decision-making process, the Adams No. 1 generating station at Niagara Falls began transferring three-phase alternating current power to Buffalo at 11 kV. Following completion of the Niagara Falls project, new power systems increasingly chose alternating current as opposed to direct current for electrical transmission.11
Developments in power systems continued beyond the nineteenth century. In 1936 the first experimental HVDC (high voltage direct current) line using mercury arc valves was built between Schenectady and Mechanicville, New York. HVDC had previously been achieved by series-connected direct current generators and motors (the Thury system) although this suffered from serious reliability issues.12 In 1957 Siemens demonstrated the first solid-state rectifier, but it was not until the early 1970s that solid-state devices became the standard in HVDC.13 In recent times, many important developments have come from extending innovations in the ICT field to the power engineering field. For example, the development of computers meant load flow studies could be run more efficiently allowing for much better planning of power systems. Advances in information technology and telecommunication also allowed for remote control of a power system's switchgear and generators.
Worth to know
Electrical contractors employ workers in many capacities, determined by their level of training and experience. Some common jobs include:
Apprentice Electrician ? Receives on-the-job training and classroom instruction from licensed journeymen or master electricians about how to install, modify, repair, and maintain power and lighting systems. Most apprentice programs last 3 to 5 years and apprentices earn wages during this training period.2
Journeyman Electrician ? Installs, modifies, repairs, and maintains power and lighting systems. Reads blueprints, terminates cable, and installs and troubleshoots control wiring from drawings. Has completed the apprentice program and holds a journeyman's license (according to state requirements) and supervises apprentices.
Estimator ? Calculates a project's duration and cost, including materials, overhead, and labor. This estimate is often submitted as a bid on a project and serves as a scheduling and budget guideline as the project proceeds.
Project Supervisor ? Oversees workforce to encourage safe and high-quality installations. Monitors progress to meet project deadlines. Submits required reports and forms.
An electrical contractor
An electrical contractor is a business person or firm that performs specialized construction work related to the design, installation, and maintenance of electrical systems?a $130 billion industry in the United States.1
An electrical contractor is different from an electrician; an electrician is an individual tradesman and an electrical contractor is a business person or company that employs electricians. Both usually hold licenses and insurances to properly and safely operate a business, protecting the employees and home owners/business owners from insurance liabilities. These requirements vary from state to state. Electricians may work for an electrical contractor, or directly for individuals or companies.