Electric power systems

From an overall physical perspective, power systems consist of a number of nodes (substations and power plants) which are typically interconnected by redundant networks of transmission and sub-transmission lines forming a grid network, often called loop systems. Emanating from some nodes (distribution substations) are radial systems (tree networks) of feeder lines and service lines that carry power to users. It should be noted that nomenclature used to define some parts of the system varies between utilities within the U.S. and from country to country. It should also be noted that in the descriptions that follow, typical facilities and situations will be discussed. Some utilities organize their systems in different ways to better address their particular needs. The objective of this paper is to provide the earthquake investigator with some familiarity with power systems and not to create a power system specialist