2×300MW火力发电厂设计 电气工程及其自动化毕业论文外文文献

广东工业大学华立学院

本科毕业设计（论文）

外文参考文献译文及原文

系部机电与信息工程学部

专业电气工程及其自动化

年级2009级

班级名称

学号

学生姓名

指导教师

2013年5月

目录

1外文文献译文(1) (1)

2外文文献原文(1) (4)

3外文文献译文(2) (8)

4外文文献原文(2) (13)

外文文献译文

1火力发电厂设计规程（DL5000-2000）

1.1前言

本规程为条文强制性行业标准，其中划下线的条文为强制性条文，表格中有强制性内容时，在表注中提示。

DL5000-1994《火力发电厂设计技术规程》自颁布实施以来，对电力建设中贯彻国家的基本建设方针，体现经济政策和技术政策，统一明确建设标准，保证扩建的火力发电厂技术先进，实现安全、经济、满发、稳发和满足环保要求起到了积极作用，收到了良好效果。

随着改革的深入和技术的进步，DL5000-1994在有些方面已经不能适应电力建设发展的要求，根据国家经济贸易委员会电力司电力[1999]40号文《关于确认1998年度电力行业标准制、修订计划项目的通知》中第42项的安排，电力规划设计总院组织力量对DL5000-1994进行了修编。

本次修编工作，贯彻了电力建设的基本方针，认真落实“安全可靠、经济适用、符合国情”的政策和控制工程造价的一系列措施，积极推广技术先进、成熟可靠的设计技术，注重节煤、节水、节电、节地和控制非生产性设施的规模和标准，注意与社会主义市场经济体制相适应，为电力建设进入21世纪作好设计技术准备。

本次修编，未对DL5000-1994的框架进行大的修改，仅对有关章节的内容进行了修改、删除和补充，并对部分章节进行适当调整。

推广应用燃气-蒸汽联合循环发电技术，烟气脱硫技术和洁净煤发电技术是21世纪电力的发展方向，但与常规燃煤发电技术相比，国内实践经验较少，尚欠成熟。对次，本次修编从前瞻性出发，仅编写了部分比较成熟的条文。

本规程由国家电力公司提出。

本规程负责起草单位：中国电力建设工程咨询公司。

本规程委托中国电力建设咨询公司负责解释。

1.2范围

本规程规定了大型火力发电厂设计应遵循的原则与建设标准。本规程适用于汽轮发电机组容量为125MW—600MW级机组的凝汽式火力发电厂，也适用于50MW级及以

上供热式机组的热电厂设计。600MW级及以上的机组可参照使用。本规程适用于新建或扩建电厂的设计，改建工程的设计可参照使用。

1.3总则

发电厂的机组容量应根据系统规划容量、负荷增长速度和电网结构等因素进行选择。应选用高效率的大容量机组，但最大机组容量不宜超过系统总容量的10%。

发电厂的机组台数不宜超过六台、机组容量等级不宜超过两种。同容量机、炉宜采用同一型式或改进型式，其配套设备的型式也宜一致。新建发电厂宜根据负荷需要和资金落实情况按规划容量一次建成或分两期建成。大型发电厂宜多台大容量、高效率的同型机组一次设计，连续建成。

在发电厂设计中，应对所需要的主设备、主要辅助设备和系统进行整体协调，提出技术要求，并根据同类设备的技术性能、可靠性、供货条件、价格以及制造厂的业绩和技术服务质量择优选用。在条件合适时，应优先选用标准系列产品和节能产品。

1.4厂址选择

选择发电厂厂址时，应研究电网结构、电力和热力负荷、燃料供应、水源、交通、燃料及大件设备的运输、环境保护要求、灰渣处理，出线走廊、地质、地震、地形、水文、气象、占地拆迁、施工以及周围工矿企业对电厂的影响等条件，拟订初步方案，通过全面的技术经济比较和经济效益分析，提出论证和评价。

在规划选厂阶段，当有多个推荐的厂址时，应对各厂址的建设顺序和规模提出意见。

在选定厂址时，应对建设规模和建成期限提出意见，并对装机容量提出建议。

选择电厂厂址时，应充分考虑发电厂达到规划容量时接入系统的出线条件。

1.5主厂房布置

常规的主厂房宜按锅炉房、煤仓间、除氧间（或合并的除氧煤仓间）、汽机房的顺序布置，其主要尺寸不宜超过同类机组主厂房参考设计的尺寸。根据工程具体条件，在经技术经济论证合理时，也可采用其它既能控制工程造价又有利运行检修和施工新的布置形式。

在非严寒地区，锅炉宜采用露天或半露天布置。对严寒或风沙大的地区，当采用塔式锅炉时，宜采用紧身罩封闭；对非塔式锅炉应根据设备特点及工程具体情况采用紧身罩或屋内式布置。在气候条件适宜地区，对密封良好的锅炉也可采用炉顶不设小室和防雨罩的布置方式。

1.6锅炉设备及系统

锅炉设备的选型和技术要求应符合SD268-1988《燃煤电站锅炉技术条件》的规定。锅炉设备的型式必须适应燃用煤种的煤质特性及现行规定中的煤质允许变化范围。对燃煤及其灰分应进行物理、化学试验与分析，取得煤质的常规特性数据和非常规特性数据。

大容量机组锅炉过热器出口至汽轮机进口的压降宜为汽轮机额定进汽压力的5％；过热器出口额定蒸汽温度对于亚临界及以下参数机组宜比汽轮机额定进汽温度高3℃；对于超临界参数机组宜比汽轮机额定进汽温度高5℃。冷段再热蒸汽管道、再热器、热段再热蒸汽管道额定工况下的压力降宜分别为汽轮机额定工况高压缸排汽压力的1.5％～2.0％，5％，3.5％～3.0％；再热器出口额定蒸汽温度比汽轮机中压缸额定进汽温度宜高2℃。

锅炉燃烧制粉系统与设备的设计，应与锅炉本体设计及锅炉安全保护监控系统相适应，并必须符合DL435《火电厂煤粉锅炉燃烧室防爆规程》的规定。

外文文献原文

1Technical Code Designing Fossil Fuel Power Plants

1.1Foreword

This code is a professional standard containing compulsory articles,and those articles are https://www.360docs.net/doc/7c3707899.html,pulsory content in tables is indicated by notes for the table.

Since the issuance and implementation,DL5000—1994“Technical code for designing fossil fuel power plants”has played a positive role and achieved good effects in carrying out the capital construction policies of the state,reflecting the economic and technical policies, unifying and defining construction standards,ensuring adoption of advanced technology in the newly built and expanded fossil fuel power plants,realizing safe,economic,full load and steady operation and satisfying the environmental protection requirements in the construction of electric power facilities.

With the deepening of reform and advance of technology,some aspects of DL5000—1994can no longer meet the requirements in the development of construction of electric power facilities.According to the arrangement in Item42of the document NO.[1999] 40“Notice on confirming standard system and revision plan item in electric power industry in 1998”of the Department of Electric Power of the State Economic and Trade Commission,the Electric Power Planning and Design General Institute organized people to conduct the revision and compilation of DL5000—1994.

In this revision and compilation,the basic policies on electric power construction have been carried out,the policy on“safe and reliable,economic and complying with national conditions”and a series of measure to control project cost conscientiously implemented,and mature and reliable design technology adopting advanced techniques actively popularized, with due consideration given to saving coal,water,power and land and controlling the size and standard of non-production facilities.Attention has been paid to adapting to the socialist market economic system,to get well prepared in design and technology for the electric power construction in the21st century.

In this revision and compilation,no major revision has been made to the framework of

DL5000—1994,only some revision,deletion and supplement have been made to the contents of relevant section,and some sections have been adjusted as appropriate.

To spreading and application of gas-steam combined recycling power generation technology,flue gas desulfurization technology and clean coal power generation technology are the development orientation of the power industry in the21st century,however,compared with the conventional coal-firing power generation technology,they are not so mature as there is not much practical experience in the country.Therefore,in this revision and compilation,only some fairly mature articles were prepared for perspective.

This code was proposed by the State Electric Power Corporation.

This code shall be under the charge by China Electric Power Planning and Design Association.

This code shall be interpreted by China Electric Power Planning and Design Association.

1.2Scope

This code has specified the principles that should be followed and the construction standards in the design of large sized fossil fuel power plants.This code is applicable to the design of condensing type fossil fuel power plants with units of turbo-generator sets at capacity of125MW—600MW,as well as fossil fuel power plants with heat supplying units at or above50MW.It can be used as reference for units of and above600MW.This code is applicable to the design of newly built or extension of power plants,and can be used as reference for the design of modification projects.

1.3General Provisions

The unit capacity of power plants shall be selected in accordance with such factors as the system planning capacity,load increase rate and grid https://www.360docs.net/doc/7c3707899.html,rge capacity unit with high efficiency shall be selected,provided that maximum unit capacity should not exceed 10%of the total system capacity.

There should be no more than six units in a power plant,with no more than capacity grades for the units.Turbo-generators and boilers of the same capacity should be of same type or modified type,and with the same types of associated equipment.A newly built power

plant should be built in one or two phases to the planned capacity on the basis of load demand and available capital high-efficiency unit of the same type,and be constructed successively.

In power plant design,overall coordination shall be made and technical requirements shall be raised on the main auxiliary equipment and systems required,and selection shall be made among the same type of equipment on the basis of technical performance,reliability, supply conditions,prices and performance and technical service quality of manufactures. When conditions are standard series products and energy-saving products shall be selected in priority.

1.4Site Selection

In site selection for power plants,the following condition shall be studied:grid configuration,power and heat load,fuel supply,water source,traffic,transport of fuel and large equipment,environmental protection requirements,disposal of fly ash and slag, outgoing line corridor,geology,seismology,topography,hydrology,meteorology,land requisition and relocation,construction,and influence of surrounding industrial and mining enterprise on the power plants,so that preliminary schemes can be drawn up and justification and evaluation can be made through overall technical and economic comparison and economic efficiency analysis.

In the site selection for planning,comments shall be made on the construction scale and completion time,with proposal on the number and capacity of units to be installed.

In the site selection for engineering,comments shall be made on the construction scale and completion time,with proposal on the number and capacity of units to be installed.

In selecting power plant sites,full consideration shall be given to the outgoing conditions for connection with the grid when the power plants reach the planned capacity. 1.5Arrangement of Main Building

The main buildings should be arranged in the order of boiler house,coal bunker bay, deaerator bay(or combined coal bunker and deaerator bay)and turbine,and their size should not exceed those of the reference design for main buildings for units of the same category. When it is deemed reasonable after technical and economic justification and according to the actual project conditions,other new forms of arrangement that can control project cost and

favorable to operation,maintenance and construction can also be adopted.The comparable building volume of main building shall not exceed data of reference design of main buildings for units of the same category.

In non-severely cold regions,boilers should be in open or semi-open arrangement.In areas with severe cold or strong sandstorm,tower type boilers should be tightly enclosed with outer wall boards,and non-tower type boilers shall either be tightly enclose with outer wall boards or be arranged indoor according to the equipment features and actual condition of the project.In regions with proper climate conditions,boilers with good sealing can be arranged without top compartment and rain shield.

1.6Boiler Equipment and Systems

The type selection of boiler equipment and technical requirements shall be as specified in“Technical Specification for Coal Fired Power Plant Boiler”SD268-1988.The type of the boiler equipment must be suited to the quality characteristics of the coal used and the allowable variation of the coal quality in the current specifications.The physical and chemical tests and analyses of the coal and its ash shall be performed to obtain the normal and abnormal characteristic data of the coal quality.

The pressure drop from the superheater outlet of the large capacity boiler to the turbine inlet shall be5%of the rated inlet steam pressure of the turbine.For the unit with subcritical and below parameters,the rated steam temperature at the superheater outlet shall be3℃higher than the rated inlet steam temperature of the turbine.At rated conditions,the pressure drops of the cold reheat steam piping,reheater and hot reheat steam piping shall be 1.5%~2.0%.5%,3.5%~3.0%respectively,of the HP turbine exhaust steam pressure at the operation conditions.The rated steam temperature at the reheater outlet shall be2℃higher than the rated inlet steam temperature of the IP turbine.

The design of the pulverizing system for boiler combustion and equipment shall be in accordance with the design of the boiler proper and its safety protection monitoring system and shall conform with the specifications is“Anti-explosive Directories of Pulverized Coal Boiler Combustion Chamber of Fossil fuel power plant”DL345.

外文文献译文

2在电力系统保护中自适应继电保护的进步

2.1摘要

在美国配电系统被认为是存在的最复杂的机器之一。电气现象，在这样一个复杂的系统，可以造成严重的自我伤害。这就需要防止损坏保护方案。直到最近，有一个安全的能力提供动力和需求之间的差距。因此，这些保护方案集中在可靠性上允许的断开线，变压器或其它设备隔离发生故障的元件的目的。而在某些情况下，断开是没有必要的。另一个极端的可靠性要求安全性。这方面的可靠性要求仅用于保护预定区域内的故障保护装置的操作。这里有一个权衡，可靠的保护方案无疑将会防止损坏，很容易出现不必要的操作，这可能会导致级联中断。

安全计划不会不必要的操作，继电器无法正常运行时，该系统零件容易出现损坏。基于微处理器的继电计划，重点是可以实现的混合动力可靠性通过自适应中继。自适应继电保护介绍保障计划调整设置和/或系统当时的条件基础上的操作逻辑。这些调整可以帮助避免继电器的误动作。

调整可包括，但不限于，事后分析的数据记录了在整个系统中的通信以及改变继电器的参数。几个概念将被要讨论，其中之一将被实施，以证明新的工具可用的价值。2.2电力系统历史

配电在美国可以追溯到1882年9月4日，托马斯·爱迪生在曼哈顿下城开珍珠街站。

供电范围约四分之一平方英里，这直流电（DC）系统，主要用于在纽约的金融区的照明。爱迪生表明，来自中央发电站，这是能够高效地提供电力的。直流系统的问题是，最终消费者必须位于几英里范围内的发电站。问题是，使用这种类型的分布的低电压导致更高的电流和用于分发的电力线的较严重的损失。这迫使发电厂小，效率降低，这意味着，只有在人口稠密地区的小型配电系统将是有效的。

在分配系统中的电压保持恒定，线中流过的电流，取决于在用的负载。与用于分发的电力线相关的损失随着通过线路电流的平方。因此，如果电流通过两倍线路，实际上线路损失四倍。当时，爱迪生开始实施他的系统，是没有办法轻易改变的电压直流系统。

能够改变分布线的电压将允许在传输过程中减少电流,这就是被开发中的交流电系

统。交流允许变压器增加电压所需的传输，降低电压水平，安全的为最终消费者使用，这大大减少了损失的远距离输送电力。尼古拉·特斯拉是交流电技术及多相分布概念的先驱。

配电、交流和直流系统的竞争策略,导致普遍周知的电流的战役。托马斯·爱迪生,拥有直流系统专利,认为交流和与之关联的高电压是不安全的。然而,与此同时,乔治西屋是建设交流输电线路绵延数英里。这一点，连同尼古拉·特斯拉在其他方面的发展项目的一个电动机的开发,导致了交流系统的最终胜利。交流电的这一胜利导致了在配电系统我们今天有大型发电站在高电压下长距离传递能量,与原来的直流系统相比，这是既经济又有效的。然而,这的确导致至今几个工程问题的解决方案仍存在改进。

交流系统被西屋公司和特斯拉开创已经发展成为在世界上最复杂的机器之一。它的发展始于许多小型独立的系统。就可靠性而言,这些系统都是相互联系的。许多小系统的这种互联意味着数量的机器操作所需的储备在峰值负载下被降低。互联也使公用事业公司从他们的邻居中已获取最有可能便宜的电源。现在，这些互联发展成了大规模的系统。有问题的出现创造这个庞大的系统,这些问题包括更高的故障电流,在级联故障中当问题只发生在其中的一个多个小系统受影响,和一个非常微妙的平衡系统之间发生。进入这个系统的规划,特别是系统本身的保护,是非常复杂的。这个系统通常分为发电、输电、和负载。这个系统通常分为发电、输电、和负载。传动部分分为传输,二次输电及分布;各有不同的电压水平控制使用变压器。

2.3发电机

发电机用于不同形式的能量转换为电能。目前使用的大多数发电机利用磁场相互作用将机械能转化为电能。这机械能通常是提供一个旋转的原动力的形式。原动机的通常有一个磁场,其旋转的定子线圈内;定子是固定部分的发电机,转子磁场诱导电流在定子线圈。旋转的动作可以使用蒸汽涡轮机提供一些热源疮水去推动涡轮,或者对于一个水电大坝,水可以旋转涡轮机直接。有时内燃机也可以直接耦合到一个原动力。蒸汽发电厂产生他们的热量通过燃烧煤、天然气、或油以及使用核反应产生热量。如果使用一个原动机类型发电机,发电机旋转的速度是非常重要的,因为它决定了电输出频率。伟大的事情的所有类型的代为止讨论的是,他们的产出水平可以控制通过改变数量的能源投入的原动力。

其他不可控,生产的形式包括可再生能源如太阳能和风能。太阳能可以在光伏能源

需要被转换从直流到交流有助于系统,或太阳能热可以像任何其他基于结合热代。风力发电与原动力,但因为风速不恒定的电力必须适应使用电力电子,确保有正确的输出电压和频率。主要问题与这些类型的一代是没有办法来控制他们的输出,所以没有任何方法准确地预测出这些资源将贡献。另一个问题是,当小规模项目实施和饲料能量回电网,电流可以改变方向可能影响操作的某些类型的保护继电器。所以虽然也算是个不错的贡献来自可再生资源,有一种折衷的操作的可预测性。

2.4变压器

变压器是配电系统的一个重要组成部分。如前面所讨论，发电一般电压等级是在13.8KV和24KV之间。电力消费一般在110V在家庭和大型工业厂房高达4160V的电压等级之间进行。电力传输可以发生在美国的115千伏到765千伏的水平，在世界的其他地区高达1兆。变压器就是使这种大范围的电压水平的能力成为可能。没有变形金刚和能够改变电压的水平,这将是更高效的远距离传输能量。

变压器的运行基于法拉第感应定律。法拉第定律指出，如果磁通通过线圈状导体，它就会感应出电压在该导体，磁通和导体线圈匝数的导数成正比。在变压器中，磁通缠绕在铁磁芯的初级线圈引起。使用铁磁芯，得到具有高导磁率的磁通路径。然后有一个辅助线圈，该线圈缠绕在其中有一个感应电压上通过的磁通穿过核心的相同的铁磁芯。的磁通量取决于在初级线圈上的电压和匝数，二次线圈上的电压是由线圈中的磁通和线圈匝数。由于线圈匝数直接决定的初级电压，次级电压的比例，这个比例就是通常所说的匝数比。

在理想情况下，一个变压器将电压从一个层次到另一个没有任何类型的损失，但情况并非如此。变压器的损耗包括铜损，涡流损耗，磁滞损耗，漏磁通。铜损是由于与线圈导线本身的电阻，在变压器的线圈中流过的电流的平方成比例。涡电流损失的诱发不必要的电流的变压器的核心上的变压器的端子间的电压的平方成比例。磁滞损耗是由于在核心的磁畴的重排和施加到变压器的电压的函数。铜，涡流和磁滞损耗都是消费者真正的力量和被建模为阻力。漏磁通仅仅是不能被捕获由核心和被传递到在变压器的另一线圈的磁通。它是一个函数的电流流过线圈。漏磁通是消费者的无功功率和建模为感性阻抗。然而，这些损失，即会发生的传输，如果变压器是不可用的损失比较小。

2.4自适应保护方案

自适应保护方案是在保护继电器领域微处理器的应用程序和美国及世界各地的电

力系统重要性的结果。这些计划就编程而言可能具有复杂的实现方式，但他们的概念可以很容易地解释。许多这些概念只是扩张在以前的保护应用。其中几个概念将被讨论，包括以前的系统事件，本来是可以用介导帮助这些新的概念。

2.5差动保护

差动保护方案是简单地建立来检查在一个给定的实例中两个数量之间的任何差异。时间同步的限制让实施合理的保护设备和其他应用程序，直到最近出现的GPS信号很难。另一方面，从遥远的点收集到的信号系统，通信负担差动保护的实施困难或高不可攀。虽然这种类型的保护电流从一个变电站的差异，在检测到下一个可能是有用的，历史的应用程序需要两个测量值非常接近，因为通信的制约应采取的。因此，该计划是有限的一般变压器和发电机保护。基于微处理器的系统和IED之前，这两种类型的保护性质的一些问题，特别是不匹配的限制电流传感器。

比率差动保护变压器发现两个电流水平之间的差异，应接近相等。这是通过把两个电流传感器的输出并联的继电器，检测电流的流动。的电流互感器的极性的正确连接，如果两个次级电流是相等的，没有电流流经继电器。问题，这包括前面提到的不匹配，由于电流互感器的局限性，以及电流互感器错误不匹配，变压器的磁化电流，并点选变化的元素，这将改变变压器本身的有效比。这些问题得到缓解通过建立限制电流。制动电流仅仅是次级电流的平均值。该继电器动作，它认为，当电流超过一定比例的制动电流。百分比越小必需的，该继电器的灵敏度越高。

此外，磁化电流可导致通电过程中的错误和故障排除，其谐波含量以及可能会导致问题。当空载变压器的励磁涌流是造成联机时，需要获得所需的稳定状态操作发生的磁通。当故障被清除，目前的显着变化，这也有可能发生。除磁化电流，变压器过励磁也可以成为一个问题。差动继电器饱和度，在这些时候，可能会导致不必要的反应。最后，如果有故障变压器外部，它可以在不同电流水平的电流互感器饱和。如果这些饱和度之间的差异大，差动继电器的故障，是不是变压器内的不必要的操作。

基于计算机的继电器可以提供所有这些问题的解决方案的百分比差动保护方案，大大提高操作的准确性。迅速介导的事实，一台计算机可以采取任何电流互感器的输出的次级电流，以匹配所需的匝数比，并进行缩放比率不匹配所造成的主要误差。实际上，电流互感器甚至不需要有次级电流是彼此接近，但简单地采取电流足够低到计算机，一个模拟到数字的转换。然后可以选择电流互感器其准确性以及它们的饱和极限的基础

上，以防止一些讨论的其他问题。

计算机本身可以给出不同的现象，以防止不必要的操作的输入。例如，如果变压器的联机计算机可以被设置为识别和忽略的浪涌电流所带来的问题。用自来水发生变化的情况下，一台变压器，继电器可以设置为允许任何浪涌电流预期以及更改必要的比对电流互感器。某些通信参数，它甚至可以为基于计算机的差动继电器认识到变压器外部故障时会影响继电器的操作。在通信领域，也有很多机会，以提高保护方案。

外文文献原文

2The Advancement of Adaptive Relaying in Power Systems

Protection

2.1Abstract

The electrical distribution system in the United States is considered one of the most complicated machines in existence.Electrical phenomena in such a complex system can inflict serious self-harm.This requires damage prevention from protection schemes.Until recently,there was a safe gap between capacity to deliver power and the demand.Therefore, these protection schemes focused on dependability allowing the disconnection of lines, transformers,or other devices with the purpose of isolating the faulted element.On some occasions,the disconnections made were not necessary.The other extreme of reliability calls for security.This aspect of reliability calls for the operation of the protective devices only for faults within the intended area of protection.There is a tradeoff here;where a dependable protection scheme will assuredly prevent damage,it is prone to unnecessary operation which can lead to cascading outages.

Where a secure scheme will not operate unnecessarily,it is prone to pieces of the system becoming damaged when relays fail to operate properly.With microprocessor based relaying schemes,a hybrid reliability focus is attainable through adaptive relaying.Adaptive relaying describes protection schemes that adjust settings and/or logic of operations based on the prevailing conditions of the system.These adjustments can help to avoid relay miss-operation.

Adjustments could include,but are not limited to,the logging of data for post-mortem analysis,communication throughout the system,as well changing relay parameters.Several concepts will be discussed,one of which will be implemented to prove the value of the new tools available.

2.2Power Systems History

The distribution of electricity in the United States of America can be traced back to September4th,1882,when Thomas Edison opened the Pearl Street Station in lower

Manhattan.

Serving about a quarter of a square mile,this direct current(DC)system was primarily used for lighting in the financial district of New York.Edison showed that it was possible to efficiently provide electricity from a central generating station.The issue with DC systems was that the end consumer had to be located within a few miles of the generating station.The problem was that the low voltage used with this type of distribution led to higher currents and higher losses on the lines used to distribute the electricity.This forced the generating plants to be small which reduced efficiency,and it meant that only small distribution systems in densely populated areas would be effective[1].

In distribution systems the voltage is held constant and the current flowing through the lines depends on the load being served.The losses associated with the lines used to distribute the electricity vary with the square of the current running through the lines.So if the current through the lines doubles,the losses associated with the lines actually quadruples.At the time Edison started implementing his systems,there was no way to easily change the voltage in a DC system.

The ability to vary the voltage of the distribution lines would allow for the reduction of current during transmission,which was being developed within alternating current(AC) systems.AC allowed for transformers to increase the voltage required by transmission and a reduction to a voltage level that is safe for end consumers to use;this significantly reduces the losses of sending electricity over longer distances.Nikola Tesla was the pioneer of this AC technology as well as the concept of polyphase distribution[1].

These competing strategies of electrical distribution,AC and DC systems,led to what is commonly known as the Battle of the Currents.Thomas Edison,owning the patents for DC systems,argued that AC and the higher voltages associated with it was unsafe.At the same time,however,George Westinghouse was building AC transmission lines that stretched for miles.This,along with Nikola Tesla’s development of an AC motor among other developments,led to the ultimate victory of AC systems.This victory of alternating current led to the electrical distribution system we have today in which large generating stations delivering power over long distances at high voltages,which is both economical and efficient

in comparison to the original DC systems[4].This did,however,lead to several engineering issues to which solutions are still being developed today.

The AC system pioneered by Westinghouse and Tesla has developed into one of the most complex machines in the world.The growth started with many small independent systems.For reliability purposes,these systems were interconnected.This interconnection of many small systems meant that the number of machines necessary for reserve operation during peak loads was lowered.The interconnection also enabled utility companies to get the cheapest possible power from their neighbors.These interconnections grew into the massive system which we have today.There are issues that arose with the creation of this massive system;these issues include higher fault currents,cascading failures in which multiple smaller systems are affected when the problem only occurred in one of them,and a very delicate balancing act that occurs between systems.The planning that goes into this system, especially the protection of the system itself,is very complicated[5].This system is generally broken down into generation,transmission,and loads.The transmission portion is divided into transmission,subtransmission,and distribution;each having different voltage levels controlled using transformers.

2.3Generator

Generators are used to convert different forms of energy into electrical energy.Most generators in use today convert mechanical energy into electrical energy using magnetic field interactions.This mechanical energy is generally provided in the form of a spinning prime mover.The prime mover usually has a magnetic field associated with it,and its spins within the stator coils;the stator is the stationary portion of a generator,and the field on the rotor induces currents within those stator coils.The spinning action can be provided using a steam turbine where some source of heat boils water to drive that turbine,or in the case of a hydroelectric dam,water could spin a turbine directly.Sometimes internal combustion engines can also be directly coupled to a prime mover.Steam power plants generate their heat by burning coal,natural gas,or oil as well as using nuclear reactions to generate heat.In the case of using a prime mover type generator,the speed at which that generator spins is extremely important because it determines the electrical output frequency.The great thing

about all the types of generation discussed so far is that their output levels can be controlled by varying the amount of energy put into the prime movers.

Other,less controllable,forms of generation include renewables like solar and wind power.Solar power can be in the form of photovoltaic energy which needs to be converted from DC to AC to contribute to the system,or solar thermal which can be incorporated like any other thermal based generation.Wind power generates electricity with a prime mover,but because wind speeds are not constant the electricity must be conditioned using power electronics to ensure the output has the correct voltage and frequency.The main issue with these types of generation is that there is no way to control their output,so there isn’t any way to predict accurately how these sources will contribute.Another issue is that when small scale projects are implemented and feed energy back into the grid,current flow can change direction which may affect the operation of certain types of protective relays.So while it is good to have a contribution from renewable resources,there is a tradeoff in the predictability of operation.

2.4Transformers

Transformers are an essential part of the electrical distribution system,as discussed earlier.Generation is generally done at voltage levels between13.8kV and24kV. Consumption of this electricity is generally done at voltage levels between110V in homes and up to4160V in large industrial plants.Transmission of electricity can occur at levels of 115kV to765kV in the United States,and go as high as1megavolt in other parts of the world.Transformers are what make this wide range of voltage level capabilities possible. Without transformers and the ability to vary voltage levels,it would be much less efficient to transmit power over great distances.

Transformers operate based on Faraday’s law of induction.Faraday’s law states that if magnetic flux passes through a coiled conductor it will induce a voltage in that conductor that is directly proportional to the derivative of that flux and the number of turns in the conductor coil.In a transformer,a flux is induced by a primary coil that is wrapped around a ferromagnetic core.The ferromagnetic core is used to give a path to the flux that has a high permeability.There is then a secondary coil which is wrapped around the same ferromagnetic

core which has a voltage induced on it by the flux traveling through the core.The amount of flux is dependent upon the voltage and number of turns on the primary coil,and the voltage on the secondary coil is determined by the flux and the number of turns in the coil.Because the number of turns directly determines the ratio of the primary voltage to the secondary voltage,this ratio is commonly referred to as the turns ratio.

In an ideal world,a transformer would take a voltage from one level to another without any type of losses,but this isn’t the case.Transformer losses include copper losses,eddy current losses,hysteresis losses,and leakage flux.Copper losses are due to the resistance associated with the coil of wire itself and are proportional to the square of the current flowing through the coils of the transformer.Eddy currents are losses from unwanted currents induced on the core of the transformer and are proportional to the square of the voltage across the terminals of the transformer.Hysteresis losses are due to the rearrangement of magnetic domains in the core and are a function of the voltage applied to the transformer.Copper,eddy current,and hysteresis losses are all consumers of real power and are modeled as resistances. Leakage flux is simply flux that is not captured by the core and is passed to the other coil in the transformer.It is a function of the current flowing through the coils.Leakage fluxes are consumers of reactive power and are modeled as inductive impedances.These losses, however,are small in comparison to the losses that would occur in transmission if transformers were not available.

2.5Adaptive Protection Schemes

Adaptive protection schemes are the result of the application of microprocessors in the area of protective relays and are growing in importance in the electrical power systems in the United States and worldwide.These schemes may have complicated implementations as far as programming,but their concepts can be explained fairly easily.Many of these concepts are simply expansions on previous protection applications.Several of these concepts will be explored,including previous system events that could have been mediated with the help of these new concepts.

2.6Differential Protection

Differential protection schemes are set up simply to check for any difference between