Editing Electric power distribution (section)

== Primary distribution ==
Primary distribution voltages range from 4&nbsp;kV to 35&nbsp;kV phase-to-phase (2.4&nbsp;kV to 20&nbsp;kV phase-to-neutral)<ref name="eep-pdvl">{{cite web|url=http://electrical-engineering-portal.com/primary-distribution-voltage-levels|title=Primary Distribution Voltage Levels|last1=Csanyi|first1=Edvard|date=10 August 2012|website=electrical-engineering-portal.com|publisher=EEP – Electrical Engineering Portal|access-date=9 March 2017}}</ref> Only large consumers are fed directly from distribution voltages; most utility customers are connected to a transformer, which reduces the distribution voltage to the low voltage "utilization voltage", "supply voltage" or "mains voltage" used by lighting and interior wiring systems.

=== Network configurations ===
[[File:NCPC Power Plant Yellowknife Northwest Territories Canada 08.jpg|thumb|Substation near [[Yellowknife]], in the Northwest Territories, Canada]]

Distribution networks are divided into two types, radial or network.<ref>{{cite book|last=Abdelhay A. Sallam and Om P. Malik|title=Electric Distribution Systems|date=May 2011|publisher=IEEE Computer Society Press|isbn=9780470276822|page=21}}</ref> A radial system is arranged like a tree where each customer has one source of supply. A network system has multiple sources of supply operating in parallel. Spot networks are used for concentrated loads. Radial systems are commonly used in rural or suburban areas.

Radial systems usually include emergency connections where the system can be reconfigured in case of problems, such as a fault or planned maintenance. This can be done by opening and closing switches to isolate a certain section from the grid.

Long feeders experience [[voltage drop]] ([[power factor]] distortion) requiring [[capacitor]]s or [[Voltage regulator|voltage regulators]] to be installed.

Reconfiguration, by exchanging the functional links between the elements of the system, represents one of the most important measures which can improve the operational performance of a distribution system. The problem of optimization through the reconfiguration of a power distribution system, in terms of its definition, is a historical single objective problem with constraints. Since 1975, when Merlin and Back<ref>Merlin, A.; Back, H. Search for a Minimal-Loss Operating Spanning Tree Configuration in an Urban Power Distribution System. In Proceedings of the 1975 Fifth Power Systems Computer Conference (PSCC), Cambridge, UK, 1–5 September 1975; pp. 1–18.</ref>  introduced the idea of distribution system reconfiguration for active power loss reduction, until nowadays, a lot of researchers have proposed diverse methods and algorithms to solve the reconfiguration problem as a single objective problem. Some authors have proposed Pareto optimality based approaches (including active power losses and reliability indices as objectives). For this purpose, different artificial intelligence based methods have been used: microgenetic,<ref>{{Cite journal |last1=Mendoza |first1=J.E. |last2=López |first2=E.A. |last3=López |first3=M.E. |last4=Coello Coello |first4=C.A. |date=2009-09-01 |title=Microgenetic multiobjective reconfiguration algorithm considering power losses and reliability indices for medium voltage distribution network |url=https://digital-library.theiet.org/content/journals/10.1049/iet-gtd.2009.0009 |journal=IET Generation, Transmission & Distribution |language=en |volume=3 |issue=9 |pages=825–840 |doi=10.1049/iet-gtd.2009.0009 |issn=1751-8687|url-access=subscription }}</ref> branch exchange,<ref>{{Cite journal |last1=Bernardon |first1=Daniel Pinheiro |last2=Garcia |first2=Vinicius Jacques |last3=Ferreira |first3=Adriana Scheffer Quintela |last4=Canha |first4=Luciane Neves |date=2010-03-01 |title=Multicriteria Distribution Network Reconfiguration Considering Subtransmission Analysis |url=https://ieeexplore.ieee.org/document/5422823 |journal=IEEE Transactions on Power Delivery |volume=25 |issue=4 |pages=2684–2691 |doi=10.1109/TPWRD.2010.2041013 |s2cid=36322668 |issn=0885-8977|url-access=subscription }}</ref> particle swarm optimization<ref>{{Cite journal |last1=Amanulla |first1=B. |last2=Chakrabarti |first2=Saikat |last3=Singh |first3=S. N. |date=2012-01-24 |title=Reconfiguration of Power Distribution Systems Considering Reliability and Power Loss |url=https://ieeexplore.ieee.org/document/6138890 |journal=IEEE Transactions on Power Delivery |volume=27 |issue=2 |pages=918–926 |doi=10.1109/TPWRD.2011.2179950 |s2cid=21613514 |issn=0885-8977|url-access=subscription }}</ref>  and non-dominated sorting [[genetic algorithm]].<ref>{{cite journal|doi=10.3390/en6031439|doi-access=free|title=Pareto Optimal Reconfiguration of Power Distribution Systems Using a Genetic Algorithm Based on NSGA-II|year=2013|last1=Tomoiagă|first1=Bogdan|last2=Chindriş|first2=Mircea|last3=Sumper|first3=Andreas|last4=Sudria-Andreu|first4=Antoni|last5=Villafafila-Robles|first5=Roberto|journal=Energies|volume=6|issue=3|pages=1439–1455|hdl=2117/18257|hdl-access=free}}</ref>

=== Rural services ===
[[File:Red-tailed hawk on power pole-2033.jpg|thumb|High voltage power pole in rural [[Butte County, California]]]]
[[Rural electrification]] systems tend to use higher distribution voltages because of the longer distances covered by distribution lines (see [[Rural Electrification Administration]]). 7.2, 12.47, 25, and 34.5&nbsp;kV distribution is common in the United States; 11&nbsp;kV and 33&nbsp;kV are common in the UK, Australia and New Zealand; 11&nbsp;kV and 22&nbsp;kV are common in South Africa; 10, 20 and 35&nbsp;kV are common in China.<ref name="eolss">{{cite book|last1=Chan|first1=F|title=Electrical Engineering|chapter-url=http://www.eolss.net/sample-chapters/c05/e6-39a-06-01.pdf|access-date=12 March 2016|chapter=Electric Power Distribution Systems}}</ref> Other voltages are occasionally used.

Rural services normally try to minimize the number of poles and wires. It uses higher voltages (than urban distribution), which in turn permits use of galvanized steel wire. The strong steel wire allows for less expensive wide pole spacing. In rural areas a pole-mount transformer may serve only one customer. In [[New Zealand]], [[Australia]], [[Saskatchewan|Saskatchewan, Canada]], and [[South Africa]], [[Single-wire earth return]] systems (SWER) are used to electrify remote rural areas.

Three phase service provides power for large agricultural facilities, petroleum pumping facilities, water plants, or other customers that have large loads (three-phase equipment).
In North America, overhead distribution systems may be three phase, four wire, with a neutral conductor. Rural distribution system may have long runs of one phase conductor and a neutral.<ref>Donald G. Fink, H. Wayne Beatty (ed), '' Standard Handbook for Electrical Engineers, Eleventh Edition'', McGraw Hill, 1978, {{ISBN|0-07-020974-X}}, page 18-17</ref>
In other countries or in extreme rural areas the neutral wire is connected to the ground to use that as a return (single-wire earth return).