Power in an electric circuit is the rate of flow of energy past a given point of the circuit.In alternating current circuits, energy storage elements such as inductors and capacitors may result in periodic reversals of the direction of energy flow.
The portion of power due to stored energy, which returns to the source in each cycle, is known as reactive power.Źródło: https://en.wikipedia.org/wiki/AC_power
Such solutions are becoming more common due to its convenience and therefore need to repair this type of installation is becoming more common.
In 1885 George Westinghouse, an American entrepreneur, obtained the patent rights to the Gaulard Gibbs transformer and imported a number of them along with a Siemens generator and set his engineers to experimenting with them in the hopes of improving them for use in a commercial power system.One of Westinghouse's engineers, William Stanley, recognised the problem with connecting transformers in series as opposed to parallel and also realised that making the iron core of a transformer a fully enclosed loop would improve the voltage regulation of the secondary winding. Using this knowledge he built the first practical transformer based alternating current power system at Great Barrington, Massachusetts in 1886.6 Westinghouse would begin installing multi-voltage AC transformer systems in competition with the Edison company later that year.
In 1888 Westinghouse would also licensed Nikola Tesla's US patents for a polyphase AC induction motor and transformer designs and hired Tesla for one year to be a consultant at the Westinghouse Electric & Manufacturing Company's Pittsburgh labs. By 1888 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.
In the US the AC/DC competition came to the end when Edison General Electric was taken over by their chief AC rival, the Thomson-Houston Electric Company, forming General Electric.In 1895, after a protracted decision-making process, alternating current was chosen as the transmission standard with Westinghouse building the Adams No.
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. Źródło: https://en.wikipedia.org/wiki/Electric_power_system#History.