Electric Industry Utility
Posted under Industry, Power Source
Electric utilities, monopoly franchises, large central power stations, and long transmission lines have been the principal components of the prevailing electric power paradigm since the days of Insull.
Electricity generated at central power stations is almost always three-phase, ac power at voltages that typically range from about 14 kV to 24 kV. At the site of generation, transformers step up the voltage to long-distance transmission-line levels, typically in the range of 138 kV to 765 kV. Those voltages may be reduced for regional distribution using subtransmission lines that carry voltages in the range of 34.5 kV to 138 kV.
When electric power reaches major load centers, transformers located in distribution-system substations step down the voltage to levels typically between 4.16 kV and 34.5 kV, with 12.47 kV being the most common. Feeder lines carry power from distribution substations to the final customers.
On power poles or in concrete-pad-mounted boxes, transformers again drop voltage to levels suitable for residential, commercial, and industrial uses.
Entities that provide electric power can be categorized as utilities or nonutilities depending on now their business is organized and regulated.
Electric utilities traditionally have been given a monopoly franchise over a fixed geographical area. In exchange for that franchise, they have been subject to regulation by State and Federal agencies. A few large utilities are vertically integrated; that is, they own generation, transmission, and distribution infrastructure.
Most, however, are just distribution utilities that purchase wholesale power, which they sell to their retail customers using their monopoly distribution system. The roughly 3200 utilities in the United States can be subdivided into one of four categories of ownership: investor-owned, Federally owned, other publicly owned, and cooperatively owned.
About 70% of U.S. electricity is generated in power stations that use energy derived from fossil fuels—coal, natural gas, and some oil. Nuclear and hydroelectric-power account for almost all of the remaining 30%, though there is a tiny fraction supplied by nonhydroelectric renewables.
The energy going into power plants is referred to as primary energy to distinguish it from end use energy, which is the energy content of electricity that is actually delivered to customers. The numerical difference between primary and end-use energy is made up of losses during the conversion of fuel to electricity, losses in the transmission and distribution system (T&D), and energy used at the power plant itself for its own needs.
Less than one-third of primary energy actually ends up in the form of electricity delivered to customers. For rough approximations, it is reasonable to estimate that for every 3 units of fuel into power plants, 2 units are wasted and 1 unit is delivered to end-users.