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Protective Relaying, 4th Edition by Thomas J. Domin, J. Lewis Blackburn

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Chapte r12

Line Protection

12.1 Classifications of Lines and Feeders

Lines provide the links—the connections—between the various parts of the power system and the associated equipment. Power generated at low voltages is stepped up to higher voltages for transmission to various stations, where it is stepped down for distribution to industrial, commercial, and residential users.

Most power systems have two to many voltage levels. Over the 100-year history of AC systems, the actual three-phase voltages used have varied considerably, with no international standards. In the United States, the IEEE Standards Board adopted a set of standards in 1975 proposed by the Industrial Applications Society (IAS). These are summarized in Table 12.1. The class ...

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