Editing Electric power distribution (section)

{{Short description|Final stage of electricity delivery to individual consumers in a power grid}}
[[File:Polemount-singlephase-closeup.jpg|thumb|upright|A 50&nbsp;kVA pole-mounted distribution transformer ]]

'''Electric power distribution''' is the final stage in the [[Power delivery|delivery of electricity]]. Electricity is carried from the [[Electric power transmission|transmission system]] to individual consumers. Distribution [[Electrical substation|substations]] connect to the transmission system and lower the transmission voltage to '''medium voltage''' ranging between {{val|2|ul=kV}} and {{val|33|u=kV}} with the use of [[transformer]]s.<ref name="Short2014"/> ''Primary'' distribution lines carry this medium voltage power to [[distribution transformer]]s located near the customer's premises. Distribution transformers again lower the voltage to the [[utilization voltage]] used by lighting, industrial equipment and household appliances. Often several customers are supplied from one transformer through ''secondary'' distribution lines. Commercial and residential customers are connected to the secondary distribution lines through [[service drop]]s. Customers demanding a much larger amount of power may be connected directly to the primary distribution level or the [[subtransmission]] level.<ref name=HSW/>

[[File:Electricity Grid Schematic English.svg|thumb|upright=1.2|General layout of [[Grid (electricity)|electricity networks]]. The voltages and loadings are typical of a European network (in Canada, for example, Extra High Voltage can mean 735kV.) ]]
The transition from transmission to distribution happens in a power [[Electrical substation|substation]], which has the following functions:<ref name=HSW>{{Cite web|url=http://science.howstuffworks.com/environmental/energy/power5.htm|title=How Power Grids Work|website=HowStuffWorks|access-date=2016-03-18|date=April 2000}}</ref>
* [[Circuit breaker]]s and switches enable the substation to be disconnected from the [[Electrical grid|transmission grid]] or for distribution lines to be disconnected.
* Transformers step down transmission voltages, {{val|35|u=kV}} or more, down to primary distribution voltages. These are medium voltage circuits, usually {{val|600|-|35000|u=V}}.<ref name="Short2014">{{Cite book|title=Electric Power Distribution Handbook|last1=Short|first1=T.A.|publisher=CRC Press|year=2014|isbn=978-1-4665-9865-2|location=Boca Raton, Florida, USA|pages=1–33}}</ref>
* From the transformer, power goes to the [[busbar]] that can split the distribution power off in multiple directions. The bus distributes power to distribution lines, which fan out to customers.
Urban distribution is mainly underground, sometimes in [[common utility duct]]s. Rural distribution is mostly above ground with [[utility pole]]s, and suburban distribution is a mix.<ref name="Short2014" />
Closer to the customer, a distribution transformer steps the primary distribution power down to a low-voltage secondary circuit, usually 120/240 V in the US for residential customers. The power comes to the customer via a [[service drop]] and an [[electricity meter]]. The final circuit in an urban system may be less than {{convert|50|ft|m|order=flip}} but may be over {{convert|300|ft|m|order=flip}} for a rural customer.<ref name="Short2014" />