ABSTRACT
The overhead transmission lines are used in open areas such as interconnections between cities or along wide roads within the city. In congested areas within cities, underground cables are used for electric energy transmission. The distribution transformer reduces the voltage to 230/115 V, which supplies houses, shopping centers, and other local loads. Typical subtransmission lines interconnect the high-voltage substations with distribution stations within a city. Many distribution lines in the United States have been built with a wood pole and cross arm. The voltage between the phase conductor and ground, called line-to-ground voltage, is equal to the line-to-line voltage divided by the square root of three. The generating station converts the stored energy of gas, oil, coal, nuclear fuel, or water position to electric energy. The generator is connected directly to the low-voltage winding of the main transformer. Most newly developed residential areas are supplied by 12 kV cables through pad-mounted step-down transformers.
