A2.1配电系统毕业论文外文翻译

1、外文资料翻译A2.1配电系统 （译文）配电网是电力输送到用户的最后阶段。配电系统的网络是将传输系统中的电力传递给消费者。通常情况下，配电网络将包括中压（1KV 至 72.5kV ）电力线路、变电站和柱上变压器、低压（小于1 kV ）配电线路和电能表计。历史在电力分配的早期，直流（DC）发电机以相同的电压连接到负载。发电设备、传输和负载必须是相同的电压，因为没有办法改变直流电压水平，除非改变电动机发电机组电压。直流低电压（100 伏）这是主要的电力负荷白炽灯的实际电压。低电压配电建筑也需要安全绝缘。电缆的损耗与电流的平方，与电缆的电阻成正比。更高的传输电压会增加已有铜线的传输电能的能力，但没有有

2、效的方法改变直流电源电路的电压等级。为了提高经济实用减小损失产生的采用粗电缆和本地发电机的爱迪生直流系统。早期的直流发电厂距离最远的客户距离一般大约为在1.5 英里（ 2.4 公里）从而避免过于庞大和昂贵的导体。交流电的介绍直接电流之间的竞争（DC）和交流（ AC）（在美国，分别以托马斯爱迪生和乔治西屋为代表）被称为电流的战争。在相互的竞争中，交流成为传输功率的主要形式。安装在发电站的电力变压器，可以用来提高发电机的电压，并利用当地的变电站的变压器降低电压以便供电。增加电压以便降低当前输电和配电线路导体的损失，这使得长距离电力输配电更经济，发电机（如水电站）可以远离负荷所在地。配电系统差异北美

3、和欧洲的配电系统有所不同，北美的系统往往有更大数量的低电压的降压变压器靠近客户的场所。例如，在美国， 一杆安装在一个郊区设置变压器可供7-11 的房子， 而在英国一个典型的城市或郊区的低压变电站通常是额定315 千瓦和 1 MVA，供应着整个邻里之间。这是因为欧洲应用的高电压（415 V 与 230 V）可以以较低的功率损耗传输较大的距离。在北美建立的防守的优点是，在一个单一的变压器故障或维护时，只会影响较少的客户。英国的安装方式的优点是变压器可能更少，更大和更有效的减少备用容量，减少电力浪费以便满足多样性的需求。北美的城市地区划分成很多客户区域，形成网络分布并且用多个变压器和低压母线将街区连

4、接在一起。农村电气化系统， 因为长距离的配电线路覆盖使得城市系统相比更倾向于使用更高的电压，（见农村电气化管理局） 。7.2 ，12.47 ，25，和 34.5 kV 是美国常见的配电电压； 11 kV 和 33 kV 电压等级在英国、新西兰和澳大利亚很常见； 11 kV 和 22 kV 在南非很常见的；其他电压等级偶尔使用。在新西兰，澳大利亚，萨斯喀彻温省，加拿大，南非偏远的农村地区采用单线接地回路系统（SWER）。电力电子技术现在允许直流电压电压等级的转换，交流在配电网中的应用是因为经济优势，效率和可靠的变压器。高压直流应用于在大范围、远距离的输电，或用于连接相邻的交流网络，而不是分配电能

5、给客户。电力通常是在发电站产生的11-25kv 电压长然后升高到400 千伏， 220 千伏或 132 千伏通过高压线传输网络进行远距离传输。通常，这些线路传递电能到数百公里成为一个共同的电源称为网格。网格一般通过 33kv 子传输网络（或有时66kV）线连接到负荷中心（市）。这些网格线终点在33kV（有时66kV）变电站，并且降压至11kV 或更低，通过11kV 电压配电网传送到负荷点。现代配电系统现代配电系统开始于配电站, 通过电能表的辅助服务最终传递到用户的插座中。配电线路服务于很多的用户。从 2300 到 35000 伏特选择适合电压使用于短距离配电线路取决于功能标准，传输距离不同，服

6、务的负荷。配电网由安置在变电站的变压器提供电能，其中降低高电压是用于电力配电传输。传输电能的导体布可以是架空杆线，或在被埋入人口稠密的地区地下的电缆。城市和郊区的住宅，商业，工业的配电负荷为三相制。在农村地区因为较少的客户配电可采用单线制以保证经济性。只有大的消费者是直接从配电网中获得电能；大部分客户都连接到一个变压器，降低了配电电压以供照明和室内配电系统使用。变压器可以安装线杆上或设置防护栏安置在地面上。在农村地区，一个电杆上变压器可能只有一个客户，但在更密集的地区可能有多个客户连接。在非常密集的城市地区，由许多变压器通过总线相互连接形成二级网络。 每个客户都引下线和计费表。 （很小的负载只

7、每月收取费用， 如庭院灯、仪表。）接地系统连接到大地通常是供电系统提供给客户以便设备需要接地。对客户的系统连接到接地的目的是限制过电压，如高压导线落在低电压的导体，或配电变压器内发生故障。如果所有的导电物体结合到同一个接地系统，会减小触电的风险。然而，混乱的连接与接地线路的错乱问题可能会导致客户的管道，游泳池或其他设备出现的电压。通常这些来自以外的其他客户的处所的地方问题很难解决。国际差异在许多地区，三相三角形接线是很常见的。三角形接线没有中性线而很便宜。在北美国和拉丁美洲的美国，三相通常是Y 形接线，中性点直接接在发电机转子的中心处。配电变压器中性点经过低电阻接地。形接线是采用一般绝缘三相四

8、线制。三相Y 形接线在电机和大功率设备的应用表现优异。世界上在住宅和轻工业服务的许多领域使用单相220 V 或 230 V 。在这个系统中，高压配电网的单位面积内都有几个变电站直接分配230 V 电源。三项中的火线和一个零线连接到建筑物。单相配电常用负荷比较小的地方。北美在美国和加拿大等国家，分阶段的服务是最常见的。分阶段只提供120 V 和 240 V 的三相制服务。用户的电压由当地变压器提供。中性点直接连接到三相接线中性点。插座电压只有120 V ，但高负荷的设备因为采用两个不同的相位而使用240V。欧洲在欧洲，工业和家庭使用的配电网是三相四线制系统。三相电压为400 伏和单相电压230

9、伏。有的工业客户采用三相电压为690 / 400伏。日本Y日本拥有大量小型工业制造商，因此许多郊区采用低于标准低压三相电压。同时，日本的正常供应的住宅为三相中的两相外加一条中性线。这些电压对照明和电动机工作提供很好的前提。农村服务农村供电通常尽量减少极线的数目。一根线单线接地回路（ SWER）是最昂贵的。它使用高电压，从而允许使用镀锌钢线。结实的廉价钢线允许很长的间距。其他地区使用高压分相导线或三相导线供电成本都较高。计量电能表根据不同的电气服务的形式使用不同的计量方程。由于不同的服务，在计能表的导线和传感器的数量上也有所不同。条款除了指的是物理布线，电气服务这个词也指在抽象意义上的对建筑提供

10、电力。分布网络配置配电网络有两种典型的类型，径向或关联（见点网络） 。径向网络离开变电站，通过与其他相连的不成网络的供电，这是典型的对孤立负荷区供电形式。一般是在城市地区建立互联网络，发现并将供应其他多个点进行连接。这些点的连接通常是开放而允许使用的不同关闭和打开开关的配合进行操作。这些开关的操作可以通过控制中心遥控或操作员。相互连接网络好处是，在发生故障或需要维修时网络可以小面积分离保证其余网络的正常供电。在这些网络中有可能包含利用传统的电线杆和电线施工的架空线路，电缆和室内或地下变电站越来越多。然而，地下分布比建设架空线路更加的昂贵。为了减少这种成本，地下电力线有时有限放置在常见的管道中，

11、被称之为管线。来自一个变电站的配电线一般由一个断路器控制，当遇到故障则打开进行维修。自动重合闸装置可以安装进一步隔离故障线从而减少故障的影响。长供电线路按照经验要求安装电容器或电压调节器应对电压降。供应商和客户之间的合同规定给客户的供应电能的变量通常包括：?交流或直流 - 如天几乎所有的公众都是用交流电。电气化铁路用户电话交换机和工业生产过程需要大量的直流功率，如铝冶炼通常他们自己有或是相邻的专用发电设备，或使用整流器从公共交流电源转换成直流。?标准电压和波动范围（例如，5% ）?频率，通常50 或60 赫兹，一些铁路使用16.6 赫兹和25 赫兹，在一些老工业和采矿的地区采用25赫兹。?相配

12、置（单相，两相和三相相包括）?最大需量（测量在15 或 30 分钟的时间最大的平均功率需求的最大电能）?负荷系数，表示一段时间内平均负荷与高峰负荷的比。负载因素表明（投资）配电线路或系统设备的有效利用的程度。?连接负载的功率因数?接地系统TT， TN-S，TN-C-S 或 TN-C?预期短路电流?稳定性流通产业传统的电力工业一直是公有的制度，在20 世纪 70 年代开始，国家开始解除管制并开始私有化，产生了电力市场。这些主要的重点是消除前所谓输电，配电的自然垄断。因此，电力已更多的成为了商品。分离也导致发展出新的术语的来描述业新的行业（例如，线路公司，线路业务和电网公司）。译自维基百科A1.2

13、 Electric power distribution（原文）Electricity distributionis the final stage in the delivery of electricity to end users. Adistribution systems network carries electricity from the transmission system and delivers itto consumers.Typically,thenetworkwouldinclude medium-voltage(1kV to72.5kV) 1power line

14、s,substationsand pole-mountedtransformers,low-voltage(less than1kV) distributionwiring andsometimes meters.HistoryIn the early days of electricity distribution, direct current (DC) generators were connected toloads at the same voltage. The generation, transmission and loads had to be of the same vol

15、tagebecause there was no way of changing DC voltage levels, other than inefficient motor-generatorsets. Low DC voltages (around 100 volts) were used since that was a practical voltage forincandescent lamps, which were the primary electrical load. Low voltage also required lessinsulation for safe dis

16、tribution within buildings. The loss in a cable is proportional to thesquare ofthecurrent,and the resistance ofthe cable.A higher transmissionvoltagewouldreducethe copper sizeto transmita givenquantity of power, butno efficientmethod existed tochangethe voltage of DC power circuits. To keep losses t

17、o an economically practical level the EdisonDC system needed thickcablesand localgenerators.EarlyDC generatingplantsneeded to be withinabout 1.5 miles (2.4 km) of the farthest customer to avoid excessively large and expensive conductors.Introduction of alternating currentThe competitionbetweenthe di

18、rectcurrent(DC) and alternatingcurrent(AC) (intheU.S.backedby Thomas Edison and George Westinghouse respectively) was known as the War of Currents. At theconclusion of their campaigning, AC became the dominant form of transmission of power. Powertransformers,installedat power stations,could be used

19、toraise the voltage fromthegenerators,and transformersatlocalsubstationscouldreduce voltagetosupplyloads.Increasingthevoltagereduced the current in the transmission and distribution lines and hence the size of conductorsand distribution losses. This made it more economical to distribute power over l

20、ong distances.Generators (such as hydroelectric sites) could be located far from the loads.VariationsNorth Americanand European power distributionsystems alsodifferin thatNorthAmericansystemstend to have a greater number of low-voltage step-down transformers located close to customerspremises.Forexa

21、mple,in theUS a pole-mountedtransformerina suburban settingmay supply7-11houses, whereas in the UK a typical urban or suburban low-voltage substation would normally berated between 315kVA and 1MVA and supply a whole neighbourhood. This is because the highervoltageused in Europe (415V vs 230V) may be

22、 carriedovera greater distancewith acceptablepower loss. An advantage of the North American setup is that failure or maintenance on a singletransformerwillonlyaffecta few customers.AdvantagesoftheUK setuparethatthe transformersmay be fewer, larger and more efficient, and due to diversity there need

23、be less spare capacityin the transformers, reducing power waste. In North American city areas with many customers perunit area, network distribution may be used, with multiple transformers and low-voltage busesinterconnected over several city blocks.Rural electrificationsystems, incontrasttourban sy

24、stems,tendto use highervoltagesbecauseof the longer distances covered by those distribution lines (see Rural ElectrificationAdministration).7.2,12.47,25,and 34.5kV distributioniscommonintheUnitedStates;11kVand 33kV arecommon intheUK, NewZealandand Australia;11kV and 22kV arecommonin SouthAfrica. Oth

25、er voltages are occasionally used.In New Zealand, Australia, Saskatchewan, Canada, and South Africa, single wire earth return systems (SWER) are used to electrify remote rural areas.While power electronics now allow for conversion between DC voltage levels, AC is preferred indistribution due to the

26、economy, efficiency and reliability of transformers. High-voltage DC isused for transmissionof largeblocksof power over long distances,or forinterconnectingadjacentAC networks,but not for distributionto customers.Electricpower is normallygeneratedat 11-25kVin a power station. To transmit over long d

27、istances, it is then stepped-up to 400kV, 220kV or132kV as necessary.Power is carriedthrougha transmissionnetwork of high voltagelines.Usually,these linesrun intohundreds of kilometresand deliverthe power intoa commonpower poolcalledthe grid. The grid is connected to load centres (cities) through a

28、sub-transmission network ofnormally33kV (orsometimes 66kV) lines.These linesterminateintoa 33kV (or66kV) substation,where the voltage is stepped-down to 11kV for power distribution to load points through a distribution network of lines at 11kV and lower.Modern distribution systemsThe modern distribu

29、tion system begins as the primary circuit leaves the sub-station and ends asthe secondary service enters the customers meter socket by way of a service drop. Distributioncircuitsservemany customers.The voltageused isappropriatefor theshorter distanceand variesfrom 2,300 to about 35,000 volts dependi

30、ng on utility standard practice, distance, and load tobe served.Distributioncircuitsarefedfroma transformerlocatedinan electricalsubstation,where the voltage is reduced from the high values used for power transmission.Conductorsfordistributionmay be carriedon overheadpolelines,orindensely-populateda

31、reaswhere they are buried underground. Urban and suburban distribution is done with three-phasesystemstoservebothresidential,commercial,and industrialloads. Distributioninruralareasmay be only single-phase ifit is not economical toinstallthree-phase power forrelatively fewand small customers.Only la

32、rge consumers are fed directly from distribution voltages; most utility customers areconnectedto a transformer,whichreducesthedistributionvoltagetotherelativelylowvoltageused by lighting and interior wiring systems. The transformer may be pole-mounted or set on theground in a protective enclosure. I

33、n rural areas a pole-mount transformer may serve only onecustomer,butinmore built-upareas multiplecustomersmay be connected.Invery dense cityareas,a secondary network may be formed with many transformers feeding into a common bus at theutilization voltage. Each customer has a service drop connection

34、 and a meter for billing. (Somevery smallloads,such as yardlights,may be toosmallto meterand soarechargedonlya monthlyrate.)A ground connectiontolocal earth isnormallyprovidedfor thecustomers system as wellas forthe equipment owned by the utility. The purpose of connecting the customers system to gr

35、oundis to limit the voltage that may develop if high voltage conductors fall on the lower-voltageconductors, or if a failure occurs within a distribution transformer. If all conductive objectsare bonded to thesame earth groundingsystem,the riskof electric shock is minimized.However,multiple connecti

36、ons between the utility ground and customer ground can lead to stray voltageproblems;customerpiping, swimming poolsorotherequipmentmay developobjectionablevoltages.These problemsmay be difficulttoresolvesince theyoftenoriginate fromplacesotherthan thecustomers premises.International differencesIn ma

37、ny areas, delta three phase service is common. Delta service has no distributed neutralwire and is therefore less expensive. In North America and Latin America, three phase serviceis often aY() in which the neutralis directlyconnectedto thecenterofthe generator rotor.wyeThe neutralprovides a low-res

38、istancemetallic return to thedistributiontransformer.Wyeserviceis recognizable when a line has four conductors, one of which is lightly insulated. Three-phasewye service is excellent for motors and heavy power use.Many areasinthe world use single-phase220 V or230 V residentialand lightindustrialserv

39、ice.In this system, the high voltage distribution network supplies a few substations per area, and the 230 V power from each substation is directly distributed. A live (hot) wire and neutral are connected to the building from one phase of three phase service. Single-phase distribution is used where

40、motor loads are small.North AmericaIn the U.S. and partsof Canada and othercountries,splitphase serviceis the most common. Splitphase providesboth 120 V and 240 V servicewithonly threewires.The house voltagesare providedby local transformers. The neutral is directly connected to the three-phase neut

41、ral. Socket voltages are only 120 V, but 240 V is available for heavy appliances because the two halves of2a phase oppose each other.EuropeIn Europe, electricityis normallydistributedforindustryand domesticuse by the three-phase,four wire system. This gives a three-phase voltage of 400 volts and a s

42、ingle-phase voltage of230 volts. For industrial customers, 3-phase 690 / 400 volt is also available.JapanJapan has a large number of small industrial manufacturers, and therefore supplies standard low-voltage three phase-service in many suburbs. Also, Japan normally supplies residentialservice as tw

43、o phases of a three phase service, with a neutral. These work well for both lighting and motors.Rural servicesRural services normally try to minimize the number of poles and wires. Single-wire earth return (SWER) is the least expensive, with one wire. It uses high voltages, which in turn permit use

44、of galvanized steel wire. The strong steel wire permits inexpensive wide pole spacings. Other areas use high voltage split-phase or three phase service at higher cost.MeteringElectricitymeters use differentmetering equations depending on the form of electricalservice.Since themath differs from servi

45、ce to service, the number of conductors and sensors inthe metersalso vary.TermsBesides referringto the physicalwiring,the termelectricalservicealsorefersin an abstractsense to the provision of electricity to a building.Distribution network configurationsDistribution networks are typically of two typ

46、es, radial or interconnected (see spot network).A radialnetworkleavesthestationand passes throughthenetworkareawithno normalconnectionto any othersupply.Thisistypicalof long rurallineswithisolatedloadareas. An interconnectednetworkisgenerallyfoundin more urban areasand willhave multipleconnectionsto

47、 otherpointsof supply. These points of connection are normally open but allow various configurations by theoperating utility by closing and opening switches. Operation of these switches may be by remotecontrol from a control center or by a lineman. The benefit of the interconnected model is thatin t

48、he event of a fault or required maintenance a small area of network can be isolated and theremainder kept on supply.Within these networks there may be a mix of overhead line construction utilizing traditionalutility poles and wires and, increasingly, underground construction with cables and indoor o

49、rcabinet substations. However, underground distribution is significantly more expensive thanoverhead construction. In part to reduce this cost, underground power lines are sometimesco-locatedwithother utilitylinesin what arecalledcommonutilityducts.Distributionfeedersemanating from a substation are

50、generally controlled by a circuit breaker which will open whena faultis detected.Automaticcircuitreclosersmay be installedtofurthersegregatethefeederthus minimizing the impact of faults.Long feeders experiencevoltagedroprequiringcapacitorsor voltageregulatorsto be installed.Characteristics of the supply given to customers are generally mandated by contract between the supplier a