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  Chapter 2 Distribution Systems, Substations,and Integration of Distributed Generation John D. McDonald, Bartosz Wojszczyk, Byron Flynn, and Ilia Voloh Glossary Demand response Allows the management of customer consumption of electricity in response to supply conditions.Distributed generation Electric energy that is distributed to the grid frommany decentralized locations, such as from windfarms and solar panel installations.Distribution grid The part of the grid dedicated to delivering electricenergy directly to residential, commercial, and indus-trial electricity customers.Distribution managementsystemA smart grid automation technology that provides realtime about the distribution network and allows utilitiesto remotely control devices in the grid.Distribution substation Delivers electric energy to the distribution grid.Distribution system The link from the distribution substation to thecustomer. J.D. McDonald ( * )GE Energy, Digital Energy, 4200 Wildwood Parkway, Atlanta, GA 30339, USAe-mail: j.d.mcdonald@ieee.org; johnd.mcdonald@ge.com B. Wojszczyk ã B. Flynn ã I. VolohGE Energy, Digital Energy, 20 Technology Parkway, Suite 380, Norcross,GA 30092-2929, USAe-mail: Bartosz.Wojszczyk@ge.com; byron.flynn@ge.com This chapter was originally published as part of the Encyclopedia of Sustainability Scienceand Technology edited by Robert A. Meyers. DOI:10.1007/978-1-4419-0851-3M.M. Begovic (ed.),  Electrical Transmission Systems and Smart Grids:Selected Entries from the Encyclopedia of Sustainability Science and Technology ,DOI 10.1007/978-1-4614-5830-2_2, # Springer Science+Business Media New York 20137  Renewable energy Energy from natural resources such as sunlight, wind,rain, tides, biofuels, and geothermal heat, which arenaturally replenished.Smart grid A modernization of the electricity delivery system so itmonitors, protects, and automatically optimizes theoperation of its interconnected elements. Definition of the Subject This entry describes the major components of the electricity distribution system – the distribution network, substations, and associated electrical equipment andcontrols – and how incorporating automated distribution management systems,devices, and controls into the system can create a “smart grid” capable of handlingthe integration of large amounts of distributed (decentralized) generation of sus-tainable, renewable energy sources. Introduction Distributedgeneration(DG)ordecentralizedgenerationisnota newindustryconcept.In 1882, Thomas Edison built his first commercial electric plant – “Pearl Street.” ThePearl Street station provided 110 V directcurrent(DC) electric power to 59 customersin lower Manhattan. By 1887, there were 121 Edison power stations in the UnitedStates delivering DC electricity to customers. These early power plants ran on coal or water. Centralized power generation became possible when it was recognized thatalternating current (AC) electricity could be transported at relatively low costs withreduced power losses across great distances by taking advantage of the ability to raisethe voltage at the generation station and lower the voltage near customer loads. Inaddition, the concepts of improved system performance (system stability) and moreeffectivegenerationassetutilizationprovidedaplatformforwide-areagridintegration.Recently, there has been a rapidly growing interest in wide deployment of distributedgeneration, which is electricity distributed to the grid from a variety of decentralizedlocations.Commerciallyavailabletechnologiesfordistributedgenerationarebasedonwind turbines, combustion engines, micro- andmini-gas turbines,fuelcells, photovol-taic (solar) installations, low-head hydro units, and geothermal systems.Deregulationoftheelectricutilityindustry,environmentalconcernsassociatedwithtraditionalfossilfuelgenerationpowerplants,volatilityofelectricenergycosts,federaland state regulatory support of “green” energy, and rapid technological developmentsall support the proliferation of distributed generation in electric utility systems. Thegrowing rate of DG deployment also suggests that alternative energy-based solutionswill play an increasingly important role in the smart grid and modern utility. 8 J.D. McDonald et al.  Large-scaleimplementationofdistributedgenerationcanleadtotheevolutionofthedistribution network from a “passive” (local/limited automation, monitoring, andcontrol) system to an “active” (global/integrated, self-monitoring, semiautomated)systemthatautomaticallyrespondstothevariousdynamicsoftheelectricgrid,resultinginhigherefficiency,better loadmanagement,andfeweroutages.However,distributedgeneration also poses a challenge for the design, operation, and management of thepower grid because the network no longer behaves as it once did. Consequently, theplanning and operation of new systems must be approached differently, with a greater amount of attention paid to the challenges of an automated global system.This entry describes the major components and interconnected workings of theelectricity distribution system, and addresses the impact of large-scale deploymentof distributed generation on grid design, reliability, performance, and operation. Italso describes the distributed generation technology landscape, associated engi-neering and design challenges, and a vision of the modern utility. Distribution Systems Distribution systems serve as the link from the distribution substation to thecustomer. This system provides the safe and reliable transfer of electric energy tovarious customers throughout the service territory. Typical distribution systemsbegin as the medium-voltage three-phase circuit, typically about 30–60 kV, andterminate at a lower secondary three- or single-phase voltage typically below 1 kVat the customer’s premise, usually at the meter.Distributionfeedercircuitsusuallyconsistofoverheadandundergroundcircuitsina mix of branching laterals from the station to the various customers. The circuit isdesignedaroundvariousrequirementssuchasrequiredpeakload,voltage,distancetocustomers, and other local conditions such as terrain, visual regulations, or customer requirements. These various branching laterals can be operated in a radial configura-tionor asa loopedconfiguration, where two ormoreparts ofthe feederare connectedtogether usually through a normally open distribution switch. High-density urbanareas are often connected in a complex distribution underground network providinga highly redundant and reliable means connecting to customers. Most three-phasesystems are for larger loads such as commercial or industrial customers. The three-phasesystemsareoftendrawnasonelineasshowninthefollowingdistributioncircuitdrawing (Fig. 2.1) of three different types of circuits.The secondary voltage in North America and parts of Latin America consists of a split single-phase service that provides the customer with 240 and 120 V, which thecustomer then connects to devices depending on their ratings. This is served fromathree-phasedistributionfeedernormallyconnectedinaYconfigurationconsistingof aneutralcenterconductorandaconductorforeachphase,typicallyassignedaletterA,B, or C.Single-phase customers are then connected by a small neighborhood distributiontransformer connected from one of the phases to neutral, reducing the voltage from 2 Distribution Systems, Substations, and Integration of Distributed Generation 9  the primary feeder voltage to the secondary split service voltage. In North America,normally 10 or fewer customers are connected to a distribution transformer.In most other parts of the world, the single-phase voltage of 220 or 230 V isprovided directly from a larger neighborhood distribution transformer. Thisprovides a secondary voltage circuit often serving hundreds of customers.Figure 2.1 shows various substations and several feeders serving customers fromthose substations. In Fig. 2.1, the primary transformers are shown as blue boxes inthe substation, various switches, breakers, or reclosers are shown as red (closed) or green (open) shapes, and fuses are shown as yellow boxes.  Distribution Devices There are several distribution devices used to improve the safety, reliability, andpower quality of the system. This section will review a few of those types of devices. Sub ALoopedUndergroundCircuitLooped MixedCircultLooped OverheadCircuitRadialOverheadCircuitRadialOverheadCircuitPad MountPad MountPole MountPole MountPole MountPole MountPad MountPole MountPole MountFuseFuseFuseFuse#1#1#1#2#2#3Sub BSub CSub D Fig. 2.1  Simple distribution system single line drawings10 J.D. McDonald et al.
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