Southern California Edison Company (SCE) is a public utility primarily engaged in the business of supplying and delivering electricity to an approximately 50,000 square mile area of southern California. SCE supplies electricity to its customers through transmission and distribution networks. Its transmission facilities, which include sub-transmission facilities and are located primarily in California but also in Nevada and Arizona, deliver power from generating sources to the distribution network and consist of lines ranging from 33 kilovolt (kV) to 500 kilovolt (kV) and substations. SCE's distribution system, which takes power from substations to customers, includes over 53,000 line miles of overhead lines, 38,000 line miles of underground lines and approximately 800 distribution substations, all of which are located in California. Edison International is the parent holding company of SCE.