History of electric power transmission

The history of the technology of moving electricity far from where it was generated dates from the late 19th century. This includes movement of electricity in bulk (formally referred to as "transmission"), and the delivery of electricity ("distribution") to individual customers. The distinction between the two terms did not exist in early years and were used interchangeably.

Prior to electricity, various systems have been used for transmission of power across large distances. Chief among them were telodynamic (cable in motion), pneumatic (pressurized air), and hydraulic (pressurized fluid) transmission.Cable cars were the most frequent example of telodynamic transmission, whose lines could extend for several miles for a single section. Pneumatic transmission was used for city power transmission systems in Paris, Birmingham, Rixdorf, Offenbach, Dresden and Buenos Aires at the beginning of the twentieth century. Cities in the 19th century also used hydraulic transmission using high pressure water mains to deliver power to factory motors. London's system delivered 7000 hp ( 5 megawatts) over a 180-mile (290 km) network of pipes carrying water at 800 psi. These systems were replaced by cheaper and more versatile electrical systems, but by the end of the 19th century, city planners and financiers were well aware of the benefits, economics, and process of establishing power transmission systems.

In the early days of electric power usage, widespread transmission of electric power had two obstacles. Firstly, devices requiring different voltages required specialized generators with their own separate lines. Street lights, electric motors in factories, power for streetcars and lights in homes are examples of the diversity of devices with voltages requiring separate systems. Secondly, generators had to be relatively near their loads (a mile or less for low voltage devices). It was known that long distance transmission was possible the higher the voltage was raised, so both problems could be solved if transforming voltages could be cheaply performed from a single universal power line.

Much of early electricity was direct current, which could not easily be increased or decreased in voltage either for long-distance transmission or for sharing a common line to be used with multiple types of electric devices. Companies simply ran different lines for the different classes of loads their inventions required, for example, Charles Brush's New York arc lamp systems required up to 10 kV for many lamps in a series circuit, Edison's incandescent lights used 110 V, streetcars built by Siemens or Sprague required large motors in the 500 volt range, whereas industrial motors in factories used still other voltages. Due to this specialization of lines, and because transmission was so inefficient, it seemed at the time that the industry would develop into what is now known as a distributed generation system with large numbers of small generators located near their loads.

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