220kV變電站電氣一次初步設(shè)計(jì) 金晶

220kV變電站電氣一次初步設(shè)計(jì) 金晶,220kV變電站電氣一次初步設(shè)計(jì),金晶,kv,變電站,電氣,一次,初步設(shè)計(jì) 華北電力大學(xué)科技學(xué)院畢 業(yè) 設(shè) 計(jì)（論 文）開 題 報(bào) 告學(xué)生姓名： 金晶 班級(jí)： 電氣07K6 所在系別： 電力工程系 所在專業(yè)： 電氣工程及其自動(dòng)化 設(shè)計(jì)（論文）題目：220kV變電站電氣一次初步設(shè)計(jì)指導(dǎo)教師： 胡永強(qiáng) 2011年 3月 4日畢 業(yè) 設(shè) 計(jì)（論 文）開 題 報(bào) 告一、結(jié)合畢業(yè)設(shè)計(jì)（論文）課題情況，根據(jù)所查閱的文獻(xiàn)資料，每人撰寫不低于2000字的文獻(xiàn)綜述。（另附）二、本課題要研究或解決的問題和擬采用的研究手段（途徑）：220kV降壓變電所電氣一次系統(tǒng)設(shè)計(jì)的主要內(nèi)容有：變電所主接線方案的確定，主變壓器的選擇，短路電流計(jì)算，電氣設(shè)備的選擇，防雷與接地系統(tǒng)設(shè)計(jì)，屋內(nèi)外配電裝置和總平面布置等。完成電氣主接線圖，電氣總平面布置圖，防雷接地圖，配電裝置斷面圖等設(shè)計(jì)圖。研究方法是：根據(jù)設(shè)計(jì)任務(wù)書的原始資料數(shù)據(jù)，以相關(guān)技術(shù)規(guī)范為標(biāo)準(zhǔn)，參考發(fā)電廠電氣部分、電力工程設(shè)計(jì)手冊(cè)等相關(guān)書籍，綜合運(yùn)用電力工程基礎(chǔ)、供用電技術(shù)等專業(yè)課程相關(guān)知識(shí)，對(duì)變電站電氣一次系統(tǒng)進(jìn)行初步設(shè)計(jì)。（1）主接線的選擇根據(jù)設(shè)備特點(diǎn)、進(jìn)出線回路數(shù)、負(fù)荷性質(zhì)等條件確定，并同時(shí)滿足運(yùn)行可靠、靈活、節(jié)約投資等要求。（2）主變壓器要根據(jù)負(fù)荷的要求選擇其臺(tái)數(shù)、容量、型號(hào)、冷卻方式等。（3）短路電流的計(jì)算依據(jù)電氣主接線圖，制定短路計(jì)算等值網(wǎng)絡(luò)圖，擬訂必要的短路計(jì)算點(diǎn)，用實(shí)用計(jì)算法計(jì)算出選擇電氣設(shè)備所需的各組短路電流。（4）主要電氣設(shè)備按正常工作條件進(jìn)行選擇，并按短路狀態(tài)來校驗(yàn)熱穩(wěn)定和動(dòng)穩(wěn)定，包括各電壓等級(jí)的母線、絕緣子、斷路器、隔離開關(guān)、電壓及電流互感器等。對(duì)“文三、指導(dǎo)教師意見：1 對(duì)“文獻(xiàn)綜述”的評(píng)語： 2對(duì)學(xué)生前期工作情況的評(píng)價(jià)（包括確定的研究方法、手段是否合理等方面）：指導(dǎo)教師： 年 月 日220kV降壓變電站電氣一次系統(tǒng)初步設(shè)計(jì)文獻(xiàn)綜述一 背景和意義 隨著經(jīng)濟(jì)的發(fā)展，工業(yè)水平的進(jìn)步，人們生活水平不斷的提高，電力系統(tǒng)在整個(gè)行業(yè)中所占比例逐漸趨大?，F(xiàn)代電力系統(tǒng)是一個(gè)巨大的、嚴(yán)密的整體。各類發(fā)電廠、變電站分工完成整個(gè)電力系統(tǒng)的發(fā)電、變電和配電的任務(wù)。1電力系統(tǒng)是國(guó)民經(jīng)濟(jì)的重要能源部門，而變電站的設(shè)計(jì)是電力工業(yè)建設(shè)中必不可少的一個(gè)項(xiàng)目。由于變電站設(shè)計(jì)內(nèi)容很多、范圍廣、邏輯性強(qiáng)，不同電壓等級(jí)，不同類型，不同性質(zhì)負(fù)荷的變電站設(shè)計(jì)時(shí)所側(cè)重的方面是不一樣的。2設(shè)計(jì)過程中要針對(duì)變電站的規(guī)模和形式，具體問題具體分析。變電站是電力系統(tǒng)中變換電壓、接受和分配電能、控制電力的流向和調(diào)整電壓的電力設(shè)施，它通過期變壓器將各級(jí)電壓的電網(wǎng)聯(lián)系起來。我國(guó)電力系統(tǒng)的變電站大致分為四類：升壓變電站，主網(wǎng)變電站，二次變電站，配電站。3我國(guó)電力工業(yè)的技術(shù)水平和管理水平正在逐步提高，對(duì)變電所的設(shè)計(jì)提出了更高的要求，更需要我們提高知識(shí)理解應(yīng)用水平，認(rèn)真對(duì)待。結(jié)合我國(guó)電力現(xiàn)狀，為國(guó)民經(jīng)濟(jì)各部門和人們生活提供充足、可靠、優(yōu)質(zhì)、廉價(jià)的電能，優(yōu)化發(fā)展變電站，規(guī)劃以220kV、110kV、10kV電影等級(jí)設(shè)計(jì)變電站。從我過目前部分地區(qū)用電發(fā)展趨勢(shì)來看，新建變電站應(yīng)充分體現(xiàn)出安全性、可靠性、經(jīng)濟(jì)性和先進(jìn)性。4在次我為了滿足某些的確 的要點(diǎn)需要，提高電能質(zhì)量。電力是能源工業(yè)，基礎(chǔ)工業(yè)，在國(guó)家建設(shè)和國(guó)民經(jīng)濟(jì)發(fā)展中占據(jù)十分重要的地位，是實(shí)現(xiàn)國(guó)家現(xiàn)代化的重點(diǎn)電能也是發(fā)展國(guó)民經(jīng)濟(jì)的基礎(chǔ)，是一種無形的，不能大量?jī)?chǔ)存的二次能源。要滿足國(guó)民經(jīng)濟(jì)發(fā)展的要求，電力工業(yè)必須超前發(fā)展，這是世界發(fā)展規(guī)律。5因此，做好電力規(guī)劃，加強(qiáng)電網(wǎng)建設(shè)，就尤為重要。而變電站在改變或調(diào)整電壓等方面在電力系統(tǒng)中起著重要的作用，它承擔(dān)著變換電壓，接受和分配電能，控制電力的的流向和調(diào)整電壓的責(zé)任。6可靠，優(yōu)質(zhì)的供電是現(xiàn)代化大都市的重要標(biāo)志。為此目的，需要采用相當(dāng)復(fù)雜的技術(shù)，其難度往往不亞于超高壓輸電技術(shù)。過去，對(duì)配電系統(tǒng)的發(fā)展未給予應(yīng)有的重視，欠賬甚多。研究采用配電新技術(shù)，提高供電的可靠性和電能質(zhì)量已是十分緊迫的任務(wù)。7二 變電站的現(xiàn)狀及發(fā)展趨勢(shì)當(dāng)今時(shí)代的變電站正趨于數(shù)字化，數(shù)字化變電站技術(shù)是變電站自動(dòng)化技術(shù)發(fā)展中具有里程碑意義的一次變革，對(duì)變電站自動(dòng)化系統(tǒng)的各方面將產(chǎn)生深遠(yuǎn)的影響。數(shù)字化變電站三個(gè)主要的特征就是“一次設(shè)備智能化，二次設(shè)備網(wǎng)絡(luò)化，符合IEC61850標(biāo)準(zhǔn)”，即數(shù)字化變電站內(nèi)的信息全部做到數(shù)字化，信息傳遞實(shí)現(xiàn)網(wǎng)絡(luò)化，通信模型達(dá)到標(biāo)準(zhǔn)化，使各種設(shè)備和功能共享統(tǒng)一的信息平臺(tái)。這使得數(shù)字化變電站在系統(tǒng)可靠性、經(jīng)濟(jì)性、維護(hù)簡(jiǎn)便性方面均比常規(guī)變電站有大幅度提升。8數(shù)字化變電站在我國(guó)發(fā)展迅速，從1995年德國(guó)提出制定IEC61850的設(shè)想開始，中國(guó)就一直關(guān)注IEC61850的發(fā)展。全國(guó)電力系統(tǒng)管理及其信息交換標(biāo)準(zhǔn)化技術(shù)委員會(huì)自2000年起，將對(duì)IEC61850的轉(zhuǎn)化作為工作重點(diǎn)之一。從CD（委員會(huì)草案）到CDV，從FDIS到正式出版物，標(biāo)委會(huì)及其工作組專家密切跟蹤IEC標(biāo)準(zhǔn)的進(jìn)展，用近5年的時(shí)間，二十多位專家的辛勤工作，完成了IEC61850到行業(yè)標(biāo)準(zhǔn)DL/T860的轉(zhuǎn)化。9標(biāo)準(zhǔn)轉(zhuǎn)化的同時(shí)，國(guó)內(nèi)頂級(jí)設(shè)備制造商如南瑞集團(tuán)、北京四方、國(guó)電南自、許繼電器等同步開展了標(biāo)準(zhǔn)研究和軟硬件開發(fā)。2006年以來，相繼有采用IEC61850標(biāo)準(zhǔn)的變電站投入運(yùn)行，從110kV到500kV，從單一廠家到多家集成，國(guó)內(nèi)對(duì)數(shù)字化變電站工程實(shí)踐的探索正在向縱深發(fā)展。在國(guó)調(diào)中心的領(lǐng)導(dǎo)下，從2004底開始，標(biāo)委會(huì)成功組織了6次大規(guī)模互操作試驗(yàn)，極大地推動(dòng)了基于IEC61850標(biāo)準(zhǔn)的設(shè)備研制和工程化。為規(guī)范IEC61850在國(guó)內(nèi)的有效有序應(yīng)用，2007年，標(biāo)委會(huì)將DL/T860標(biāo)準(zhǔn)工程實(shí)施技術(shù)規(guī)范納入工作計(jì)劃，并迅速組織有關(guān)專家進(jìn)行起草，經(jīng)廣泛征求意見，2008年該規(guī)范通過標(biāo)委會(huì)審查報(bào)批。成為指導(dǎo)DL/T860標(biāo)準(zhǔn)國(guó)內(nèi)工程實(shí)施的重要配套文件。10目前，國(guó)內(nèi)各網(wǎng)省公司都進(jìn)行了數(shù)字化變電站試點(diǎn)，對(duì)DL/T860標(biāo)準(zhǔn)的應(yīng)用程度和技術(shù)水平各不相同，有單在變電站層應(yīng)用DL/T860的，也有在過程層試驗(yàn)的，還有結(jié)合電子式互感器應(yīng)用的；有單一廠家實(shí)現(xiàn)的，也有多達(dá)十多加設(shè)備制造商參與的。數(shù)字化變電站的試點(diǎn)已經(jīng)較為充分，現(xiàn)在應(yīng)該到了總結(jié)成功經(jīng)驗(yàn)、探討發(fā)展策略的時(shí)候了。11未來，在智能電網(wǎng)建設(shè)的大背景下，數(shù)字化變電站快速發(fā)展是必然趨勢(shì)，但首先要解決電子式互感器的可靠性問題、網(wǎng)絡(luò)交換機(jī)的可靠性問題等。我國(guó)目前已建成或者在建的數(shù)字化變電站同國(guó)外的數(shù)字化變電站相比，有不同的的特點(diǎn)：國(guó)內(nèi)數(shù)字化變電站更重視可靠性問題，故較多采用冗余網(wǎng)絡(luò)方式。國(guó)內(nèi)數(shù)字化變電站較多采用IEC61850-9-1，但該標(biāo)準(zhǔn)未來非IEC主流推薦，國(guó)內(nèi)需盡快開發(fā)基于IEC61850-9-2的系統(tǒng)。因?yàn)榧夹g(shù)成熟度問題，國(guó)內(nèi)對(duì)電子式互感器的應(yīng)用還比較保守。IEC61850是面向未來的變電站自動(dòng)化技術(shù)標(biāo)準(zhǔn)，也是全世界關(guān)于變電站自動(dòng)化系統(tǒng)的第1個(gè)完整的通信標(biāo)準(zhǔn)體系，目前我國(guó)投運(yùn)的數(shù)字化變電站均以IEC61850為統(tǒng)一標(biāo)準(zhǔn)，但在對(duì)標(biāo)準(zhǔn)的理解、執(zhí)行方面還需進(jìn)一步統(tǒng)一規(guī)范。 IEC61850的概念思想非常先進(jìn)，應(yīng)該講具有很強(qiáng)的生命力和影響力。電力系統(tǒng)的其他領(lǐng)域都很重視IEC61850，有的直接引用其文本形成本領(lǐng)域的標(biāo)準(zhǔn)，有的吸收其思想，編制相關(guān)標(biāo)準(zhǔn)。IEC61850一套標(biāo)準(zhǔn)涵蓋電力系統(tǒng)各個(gè)方面是不現(xiàn)實(shí)的，但它的先進(jìn)思想和部分技術(shù)一定會(huì)被廣泛引用。由于IEC61850標(biāo)準(zhǔn)體系龐大，六次互操作，暴露出一些問題。如IEC61850標(biāo)準(zhǔn)本身描述不完全一致；各廠家對(duì)標(biāo)準(zhǔn)理解不完全相同；對(duì)應(yīng)用時(shí)的一些細(xì)節(jié)未作要求（系統(tǒng)結(jié)構(gòu)、網(wǎng)絡(luò)冗余問題、保護(hù)裝置定值的建模問題等）等。12要解決以上問題，應(yīng)該由多方共同努力完成：首先國(guó)內(nèi)的用戶和設(shè)備制造商要有統(tǒng)一標(biāo)準(zhǔn)的共同愿望，其次，標(biāo)委會(huì)要加強(qiáng)組織協(xié)調(diào)，發(fā)揮公正平臺(tái)作用。進(jìn)一步細(xì)化完善國(guó)內(nèi)工程實(shí)施技術(shù)規(guī)范，配套建立其他如功能規(guī)范、設(shè)計(jì)規(guī)范、驗(yàn)收規(guī)范等。隨著技術(shù)的不斷進(jìn)步和完善，我國(guó)數(shù)字化變電站的試點(diǎn)建設(shè)已經(jīng)有了相當(dāng)數(shù)量，有必要進(jìn)行階段性總結(jié)。所以，我們“數(shù)字化變電站應(yīng)用經(jīng)驗(yàn)高峰論壇”，想要通過此次高峰論壇，匯集國(guó)內(nèi)數(shù)字化變電站領(lǐng)域最具影響力的專家，通過交流和思想的碰撞，一定能為我國(guó)數(shù)字化變電站的發(fā)展走上健康正確的方向發(fā)揮重要作用。三 本次設(shè)計(jì)內(nèi)容變電站設(shè)計(jì)的內(nèi)容力求概念清楚，層次分明。通過大量翻閱工作，了解了電力工業(yè)的有關(guān)政策以及變電站設(shè)計(jì)技術(shù)規(guī)程等方面知識(shí)，進(jìn)而基本掌握了設(shè)計(jì)過程，結(jié)合自己設(shè)計(jì)的原始資料，提出了本次設(shè)計(jì)的思路和具體設(shè)計(jì)內(nèi)容。1.電氣主接線是變電站設(shè)計(jì)的首要部分，也是構(gòu)成電力系統(tǒng)的主要環(huán)節(jié)，主接線的擬定直接關(guān)系著變電站電氣設(shè)備的選擇、配電裝置的布置、繼電保護(hù)和自動(dòng)裝置的確定，是變電站電氣部分投資大小的決定性因素。結(jié)合原始資料分析。以及各種接線方式的優(yōu)缺點(diǎn)，適用范圍進(jìn)行綜合比較，確定出最終的接線方案.2.在變電站的選型應(yīng)根據(jù)其容量和臺(tái)數(shù)、主變壓器形式等進(jìn)行選擇。3.短路電流計(jì)算是為了更好地選擇電氣設(shè)備，繼電保護(hù)的配置及整定等，了解了電力系統(tǒng)的短路計(jì)算知識(shí)，學(xué)習(xí)了短路計(jì)算的方法，從而完成自己設(shè)計(jì)中的短路計(jì)算部分。4.導(dǎo)體及電氣設(shè)備選擇是設(shè)計(jì)的主要內(nèi)容之一，因?yàn)殡娏ο到y(tǒng)中各種電氣設(shè)備的作用和工作條件并不一樣，具體的選擇方法也不完全相同，但是對(duì)它們的基本要求是一致的，電氣設(shè)備要能可靠地工作，必須按正常工作條件進(jìn)行選擇，并按照短路狀態(tài)采取驗(yàn)熱穩(wěn)定和動(dòng)穩(wěn)定。5.高壓配電裝置在電力系統(tǒng)中起著接受和分配電能的作用，從中了解到了電氣布置知識(shí)，通過對(duì)配電的基本要求，設(shè)計(jì)原則的了解，為自己的設(shè)計(jì)做了較合理的布置。6.為了確保變電站的安全，結(jié)合防雷保護(hù)知識(shí)，防雷技術(shù)主要從兩個(gè)方面：一是雷直擊于發(fā)電廠，采取了裝設(shè)避雷針的方法；二是發(fā)電廠的雷電入侵波采取裝設(shè)閥式避雷器的防雷保護(hù)措施。7.最后參考國(guó)家電力公司農(nóng)村電網(wǎng)工程典型設(shè)計(jì)（第二分冊(cè)）、電氣CAD書籍知識(shí)，了解我國(guó)在發(fā)電廠設(shè)計(jì)工作中電氣具體的布置規(guī)劃，同時(shí)參考其繪圖，編號(hào)等要求，為自己的設(shè)計(jì)繪制了主接線圖、平面圖和斷面圖。參考文獻(xiàn)1 熊信銀.發(fā)電廠電氣部分M.中國(guó)電力出版社, 20042 宋繼承.220500KV變電所二次接線.中國(guó)電力出版, 19963 劉笙.電氣工程基礎(chǔ)M.科學(xué)出版社, 20024 水利電力部西北電力設(shè)計(jì)院.電氣工程設(shè)計(jì)手冊(cè)電氣一次部分M.中國(guó)電力出 版社, 19895 電力工業(yè)部西北電力設(shè)計(jì)院.電氣工程設(shè)計(jì)手冊(cè)電氣一次部分M.中國(guó)電力出 版社, 19986 文鋒.現(xiàn)代發(fā)電廠概論M.中國(guó)電力出版社, 19997 黃益莊.變電站綜合自動(dòng)化技術(shù)M .中國(guó)電力出版社, 20018 戈東方.電氣設(shè)計(jì)手冊(cè)電氣一次部分M.中國(guó)電力出版社, 20029 孟祥萍.電力系統(tǒng)分析M.高等教育出版社, 200410 陳慶紅.變電運(yùn)行M.中國(guó)電力出版社, 200511 陳生貴.電力系統(tǒng)繼電保護(hù)M.重慶大學(xué)出版社, 200312 單淵達(dá).電能系統(tǒng)基礎(chǔ).東南大學(xué)出版社,200413 張步涵.電力系統(tǒng)工程基礎(chǔ).華中科技大學(xué)出版社,200614 姚春球.發(fā)電廠電氣部分.中國(guó)電力出版社,200515 閻治安.電機(jī)學(xué).西安交通大學(xué)出版社,2003華北電力大學(xué)科技學(xué)院本科畢業(yè)設(shè)計(jì)（論文）畢 業(yè) 設(shè) 計(jì)(論文)題 目 220kV變電站電氣一次 初步設(shè)計(jì)系 別電力工程系專業(yè)班級(jí) 電氣07k6學(xué)生姓名金晶指導(dǎo)教師胡永強(qiáng)二一一年六月I220kV變電站電氣一次初步設(shè)計(jì)摘 要隨著經(jīng)濟(jì)的發(fā)展和現(xiàn)代工業(yè)建設(shè)的迅速崛起，對(duì)電能質(zhì)量、技術(shù)經(jīng)濟(jì)狀況、供電的可靠性指標(biāo)也日益提高，用電已經(jīng)成為制約我國(guó)經(jīng)濟(jì)發(fā)展的重要因素。為了保證供配電要求，供電系統(tǒng)的設(shè)計(jì)要越來越全面、系統(tǒng)，而供電系統(tǒng)的核心部分是變電所，因此設(shè)計(jì)和建造一個(gè)安全、經(jīng)濟(jì)的變電所是極為重要的。本文針對(duì)220kV變電所的特點(diǎn)，闡述了220kV變電所的設(shè)計(jì)思路、設(shè)計(jì)步驟，并進(jìn)行了相關(guān)的計(jì)算和校驗(yàn)。本次所設(shè)計(jì)的變電站是地區(qū)變電站，變電站最后規(guī)模：容量為2120MVA，容量比為100/100/50，采用三相三繞組有載調(diào)壓變壓器。220kV側(cè)本期進(jìn)線有2回，110kV本期出線6回，35kV本期出線 8回，主接線形式為220kV主接線采用雙母線分段接線，110kV主接線采用單母線帶旁路接線，35kV采用單母線分段接線。本變電站配電裝置為：220kV、110kV采用改進(jìn)半高型配電裝置，35kV采用屋內(nèi)成套配電裝置，220kV及110kV均采用斷路器單列布置。本次設(shè)計(jì)論文是以我國(guó)現(xiàn)行的各有關(guān)規(guī)范規(guī)程等技術(shù)標(biāo)準(zhǔn)為依據(jù)，所設(shè)計(jì)的是一次初步設(shè)計(jì)，根據(jù)任務(wù)書提供原始資料，參照有關(guān)資料及書籍，對(duì)各種方案進(jìn)行比較而得出。文中介紹的220kV變電站的設(shè)計(jì)方法、思路及新技術(shù)的應(yīng)用可以作為相關(guān)設(shè)計(jì)的理論指導(dǎo)。關(guān)鍵詞：變電站；設(shè)計(jì)方法；電氣主接線；配電裝置 DESIGN OF THE 220kV SUBSTATIONAbstractWith the economic development and the modern industry developments of quick rising, it also increases seriously to the dependable index of the economic condition, power supply in quantity and electricity using also becomes important of the development and supervision in our country. In order to guarantee the power supply requirements,the design of the power supply system should become more and more completely and systematic. Because the power supply system，s hard core is a transformer substation, designing and constructing a security and economical transformer substation is great importance.The text aims at the characteristics of the 220 kV substations, elaborates design way of thinking, designs step of the 220 kV substation and carries on the related calculation. This time designs the transformer substation is the local transformer substation. The transformer substation final scale: The capacity is 2*120MVA, the capacity changes into 100/100/50, uses three-phase three-winding on-load tap-changing transformer. The 220kV side that issue comes beyond a line has 2, the 110kV which issue goes beyond 10 lines, the 35kV going beyond a line, this issue 6 the main wiring form is 220kV main wiring useing the double bus segment connecting. 110kV and the 35kV uses the single bus bar partition wiring. This transformer substation power distribution equipment is: 220kV, 110kV use improved half-power distribution unit, 35kV use house set within power distribution equipment, 220kV and 110kV use the circuit breaker single row arrangement.This basis of the design is our country present technical standards and each related standard regulations and so on, designs is a preliminary design, provides the firsthand information according to the project description, the reference pertinent data and the books, carries on the comparison to each kind of plan to obtain.The text introduces the design method on way of thinking and new technique of the 220 kV substations which can be the theories of related design.Keywords: substation; method of design; Electrical main wiring; supply and distribution electricity目 錄摘 要IAbstractII目 錄11 前言12 變電站的原始資料分析22.1 變電站的類型22.2 變電站的電壓等級(jí)22.3 負(fù)荷情況22.4 進(jìn)出線情況22.5 系統(tǒng)情況22.6 環(huán)境條件23 變電站的設(shè)計(jì)33.1 電氣主接線的選擇33.1.1 電氣主接的線設(shè)計(jì)要求33.1.2 電氣主接線設(shè)計(jì)原則33.1.3 設(shè)計(jì)主接線的基本要求33.2 主接線方式的初步選擇43.2.1 幾種主接線方式簡(jiǎn)介43.2.2 選擇初步設(shè)計(jì)方案63.3 主變壓器臺(tái)數(shù)，容量及形式的選擇103.3.1 概述103.3.2 主變壓器臺(tái)數(shù)的選擇113.3.3 主變壓器容量的選擇113.3.4 主變壓器型式的選擇123.3.5 主變壓器確定134 變電站短路電流計(jì)算144.1 概述144.2 短路電流計(jì)算的目的144.3 短路電流計(jì)算的一般規(guī)定144.4 短路電流計(jì)算基準(zhǔn)值154.5 短路電流計(jì)算步驟154.6 短路電流計(jì)算165 變電站電氣設(shè)備的選擇185.1 概述185.2 斷路器的選擇195.2.1 概述19485.2.2 斷路器的選擇計(jì)算205.3 隔離開關(guān)的選擇225.4 高壓熔斷器的選擇245.5 互感器的選擇245.5.1 概述245.6 母線的選擇285.6.1 概述285.6.2 母線的選擇計(jì)算285.7.1 絕緣子選擇條件305.7.2 絕緣子選擇305.8 穿墻套管的選擇315.9 避雷器的選擇315.9.1避雷器的選擇條件315.9.2避雷器的選擇325.10 最佳方案的確定335.10.1 概述335.10.2 計(jì)算綜合投資335.10.3 計(jì)算年運(yùn)行費(fèi)用345.11 無功補(bǔ)償及補(bǔ)償裝置的選擇355.11.1 概述355.11.3 補(bǔ)償裝置容量的選擇376 電氣總平面布置及配電裝置的選擇386.1 概述386.2 電氣總平面布置427 變電站的保護(hù)設(shè)計(jì)447.1 防雷保護(hù)的設(shè)計(jì)447.2 避雷針的配置原則447.3 變電站的防雷保護(hù)設(shè)計(jì)44結(jié)論46參考文獻(xiàn)47致謝481 前言 近年來，隨著我國(guó)國(guó)民經(jīng)濟(jì)的快速增長(zhǎng)，用電也成為制約我國(guó)經(jīng)濟(jì)發(fā)展的重要因素之一，各地都在興建一系列的供配電裝置。變電站的規(guī)劃、設(shè)計(jì)與運(yùn)行的根本任務(wù)，是在國(guó)家發(fā)展計(jì)劃的統(tǒng)籌規(guī)劃下，合理的開發(fā)和利用能源，用最少的支出(含投資和運(yùn)行成本)為國(guó)民經(jīng)濟(jì)各部門和人民生活提供充足、可靠和高質(zhì)量的電能。變電站由發(fā)、送、變、配等不同環(huán)節(jié)以及相應(yīng)的通信、安全自動(dòng)、繼電保護(hù)和調(diào)度自動(dòng)化等系統(tǒng)組成，它的形成和發(fā)展，又經(jīng)歷了規(guī)劃、設(shè)計(jì)、建設(shè)和生產(chǎn)運(yùn)行等不同階段。但現(xiàn)代變電站是一個(gè)十分龐大而又高度自動(dòng)化的系統(tǒng)，在各個(gè)專業(yè)系統(tǒng)之間和各個(gè)環(huán)節(jié)之間，既相互制約又能在一定條件下相互支持和互為補(bǔ)充。為了適應(yīng)我國(guó)國(guó)民經(jīng)濟(jì)的快速增長(zhǎng)，需要密切結(jié)合我國(guó)的實(shí)際條件，從電力系統(tǒng)的全局著眼，瞻前顧后，需要設(shè)計(jì)出一系列的符合我國(guó)各個(gè)地區(qū)的用以供電的變電站，用以協(xié)調(diào)各專業(yè)系統(tǒng)和各階段有關(guān)的各項(xiàng)工作，以求取得最佳技術(shù)經(jīng)濟(jì)的綜合效益。本次畢業(yè)設(shè)計(jì)的目的就在于進(jìn)一步鞏固和運(yùn)用專業(yè)知識(shí)的能力，達(dá)到理論與實(shí)際相聯(lián)系，使所學(xué)過的專業(yè)知識(shí)具體化、形象化。本次設(shè)計(jì)可作為對(duì)所有專業(yè)課程的一次綜合能力考核。內(nèi)容為220kV地區(qū)變電所電氣一次系統(tǒng)設(shè)計(jì)，并根據(jù)變電所設(shè)計(jì)的基本原理設(shè)計(jì)，務(wù)求掌握常規(guī)變電所的電氣一次系統(tǒng)的原理及設(shè)計(jì)過程。通過對(duì)原始資料的分析、主接線的選擇及比較、短路電流的計(jì)算、主要電器設(shè)備的選擇及校驗(yàn)、線路圖的繪制以及避雷器、避雷針的選擇等步驟、最終確定了2200kV變電站所需的主要電器設(shè)備、主接線圖以及變電站防雷保護(hù)方案。2 變電站的原始資料分析2.1 變電站的類型220kV地區(qū)變電所2.2 變電站的電壓等級(jí)220/110/35 kV2.3 負(fù)荷情況110kV側(cè)：最大100MW，最小80MW， 5300小時(shí)， 0.9035 kV側(cè)：最大23MW，最小18MW， 5200小時(shí)， 0.852.4 進(jìn)出線情況220kV側(cè)：進(jìn)線2回； 110kV側(cè)：出線6回；35kV側(cè)：出線8回2.5 系統(tǒng)情況1）220kV母線電壓滿足常調(diào)壓要求；2）系統(tǒng)220kV母線的短路電流標(biāo)幺值為25（SB100MVA）；3) 110kV和35kV對(duì)端無電源2.6 環(huán)境條件1）最高溫度40C，最低溫度-25C，年平均溫度20C；2）土壤電阻率 0.93）二次額定電壓選擇電壓互感器的二次側(cè)額定電壓通常是供額定電壓為100V的儀表和繼電器的電壓繞組使用，應(yīng)滿足保護(hù)和測(cè)量使用標(biāo)準(zhǔn)儀表的要求，電壓互感器二次側(cè)額定電壓可按表5-11擇：表5-11 電壓互感器二次側(cè)額定電壓接 線型 式電網(wǎng)電壓（kV）型 式二次繞組電壓（kV）接成開口三角形輔助繞組電壓（kV）一臺(tái)PT不完全星形接 線方式335單相式100無此繞組Yo/ Yo/110J5華北電力大學(xué)科技學(xué)院畢業(yè)設(shè)計(jì)(論文)任務(wù)書所在院系 電力工程系 專業(yè)班號(hào) 電氣07k6 學(xué)生姓名 金晶 指導(dǎo)教師簽名 審批人簽字 畢業(yè)設(shè)計(jì)(論文)題目 220kV變電站電氣一次初步設(shè)計(jì) 2011年 2 月 21 日一、畢業(yè)設(shè)計(jì)(論文)主要內(nèi)容1、根據(jù)原始資料選擇57種合理的電氣主接線； 2、進(jìn)行初步技術(shù)、經(jīng)濟(jì)比較，選擇2種較好的電氣主接線；3、選擇主變壓器的容量和型號(hào)；4、計(jì)算兩種主接線的短路電流；5、根據(jù)短路電流計(jì)算結(jié)果選擇電氣設(shè)備；6、通過技術(shù)經(jīng)濟(jì)比較確定最佳方案；7、防雷系統(tǒng)設(shè)計(jì)；8、屋內(nèi)外配電裝置設(shè)計(jì)和總平面布置9、繪制圖紙：電氣主接線、電氣總平面布置、防雷與接地各一張，配電裝置斷面圖34張。二、基本要求1、進(jìn)行充分的文獻(xiàn)閱讀，了解變電站電氣一次系統(tǒng)設(shè)計(jì)的主要任務(wù)和當(dāng)前發(fā)展趨勢(shì)； 2、通過本設(shè)計(jì)，能夠綜合運(yùn)用電力工程基礎(chǔ)、供用電技術(shù)等專業(yè)課程的相關(guān)知識(shí)；3、通過電氣主接線、總平面及斷面圖的設(shè)計(jì)，加深對(duì)變電站配電裝置布置方法和原則的理解和認(rèn)識(shí)。三、設(shè)計(jì)(論文)進(jìn)度序號(hào)設(shè)計(jì)項(xiàng)目名稱完成時(shí)間備注1內(nèi)容1、2、32周2內(nèi)容4、5、63周3內(nèi)容7、83周4內(nèi)容94周5撰寫畢業(yè)論文2周設(shè)計(jì)(論文)預(yù)計(jì)完成時(shí)間： 年 月 日四、參考資料及文獻(xiàn)1、發(fā)電廠電氣部分 華中工學(xué)院2、發(fā)電廠電氣部分課程設(shè)計(jì)參考資料 天津大學(xué)3、電力工程設(shè)計(jì)手冊(cè)(14分冊(cè)) 東北西北電力設(shè)計(jì)院4、發(fā)電廠變電所電氣主接線和布置 西北電力設(shè)計(jì)院5、發(fā)電廠變電所電氣主接線設(shè)計(jì) 西安交通大學(xué)五、附錄原始數(shù)據(jù)1.變電所類型：220kV降壓變電站2.電壓等級(jí)：220/110/35kV3.負(fù)荷情況：110kV側(cè)：最大負(fù)荷100MW，最小負(fù)荷80MW，Tmax=5300小時(shí)，cos=0.935kV側(cè)：最大負(fù)荷23MW，最小負(fù)荷18MW，Tmax=5200小時(shí)，cos=0.854.進(jìn)出線情況220kV側(cè)：2回110kV側(cè)：10回 35kV側(cè)：6回5.系統(tǒng)情況（1）歸算至220kV母線的系統(tǒng)短路電抗幺值為0.35（SB100MVA）；（2）歸算至110kV母線系統(tǒng)短路電抗幺值為0.30（SB100MVA）；6.環(huán)境條件：同本地條件華 北 電 力 大 學(xué) 科 技 學(xué) 院畢 業(yè) 設(shè) 計(jì)（論 文）附 件外 文 文 獻(xiàn) 翻 譯學(xué) 號(hào)： 071901010708姓 名： 金晶 所在系別： 電力工程系 專業(yè)班級(jí)： 電氣07k6 指導(dǎo)教師： 胡永強(qiáng) 原文標(biāo)題： A survey of substation communications technology 2011 6 月3日變電站通信技術(shù)的調(diào)查 原文出處及作者：IEEE Zawada. P.J.電力變電站是電力發(fā)電中輸電和配電的一個(gè)附屬配置，在這里電壓從高壓變?yōu)榈蛪夯蛘哂傻妥兏?。電能生產(chǎn)和消費(fèi)之間可能流經(jīng)幾個(gè)變電站，并且可能改變幾次電壓等級(jí)。變電站裝有升壓變壓器的話會(huì)使電壓升高，同時(shí)減小了電流 ，而降壓變壓器降低電壓，同時(shí)提高了電流。變電站一詞在配電系統(tǒng)形成網(wǎng)絡(luò)以前就已經(jīng)出現(xiàn)。第一個(gè)變電站只連接到一個(gè)獨(dú)立的屋內(nèi)發(fā)電機(jī)，并屬于這個(gè)電站的子站。變電站的要素Substations generally contain one or more transformers, and have switching, protection and control equipment.變電站一般包含一個(gè)或多個(gè)變壓器，開關(guān)，保護(hù)和控制設(shè)備。In a large substation, circuit breakers are used to interrupt any short-circuits or overload currents that may occur on the network.在一個(gè)大型變電站中，斷路器是用來切斷任何可能出現(xiàn)的短路或過負(fù)荷電流。Smaller distribution stations may use recloser circuit breakers or fuses for protection of branch circuits.規(guī)模較小的變電站站可使用重合斷路器或熔斷器保護(hù)電路。 Substations do not (usually) have generators, although a power plant may have a substation nearby.變電站通常沒有發(fā)電機(jī)，雖然電廠可能在變電站附近。A typical substation will contain line termination structures, high-voltage switchgear , one or more power transformers , low voltage switchgear, surge protection, controls, grounding (earthing) system, and metering.一個(gè)典型的變電站將包含線路終端結(jié)構(gòu)，高壓開關(guān)，一個(gè)或多個(gè)電源變壓器 ，低壓成套開關(guān)設(shè)備，浪涌保護(hù)，控制，接地系統(tǒng)，和計(jì)量。Other devices such as power factor correction capacitors and voltage regulators may also be located at a substation.其他設(shè)備，如功率因數(shù)校正電容器和穩(wěn)壓器也可設(shè)在變電站。Substations may be on the surface in fenced enclosures, underground, or located in special-purpose buildings.變電站可建在地表上，地下，或位于特殊用途的建筑物。High-rise buildings may have indoor substations.高層建筑也可以建室內(nèi)變電站。由于外觀，或保護(hù)開關(guān)，極端氣候或污染環(huán)境的因素，Indoor substations are usually found in urban areas to reduce the noise from the transformers, for reasons of appearance, or to protect switchgear from extreme climate or pollution conditions.室內(nèi)變電站通常設(shè)在城市地區(qū)，以減少變壓器的噪音。 Where a substation has a metallic fence, it must be properly grounded (UK: earthed) to protect people from high voltages that may occur during a fault in the transmission system.變電站必須有金屬圍欄，必須妥善接地，以便在發(fā)生故障時(shí)保護(hù)人們免受高電壓的威脅。Earth faults at a substation can cause ground potential rise at the fault location.接地故障可能造成地電位升高，電流流過地面，將會(huì)在人體兩腳之間產(chǎn)生跨步電壓，這是十分危險(xiǎn)的事情。Currents flowing in the earths surface during a fault can cause metal objects to have a significantly different voltage than the ground under a persons feet; this touch potential presents a hazard of electrocution.電流流過地面 傳輸變電站 A transmission substation connects two or more transmission lines.傳輸變電站連接兩個(gè)或兩個(gè)以上的輸電線路。 The simplest case is where all transmission lines have the same voltage.最簡(jiǎn)單的情況是所有輸電線路具有相同的電壓。 In such cases, the substation contains high-voltage switches that allow lines to be connected or isolated for maintenance.在這種情況下，變電站包含高電壓開關(guān)，使線路連接或孤立進(jìn)行維修。 A transmission station may have transformers to convert between two transmission voltages, or equipment such as phase shifting transformers to control power flow between two adjacent power systems.傳輸變電站在兩個(gè)傳輸電壓或設(shè)備之間設(shè)有變壓器，如移相變壓器 ，控制功率流的兩個(gè)相鄰的電力系統(tǒng)。 Transmission substations can range from simple to complex.輸電站可以從簡(jiǎn)單到復(fù)雜。 A small switching station may be little more than a bus plus some circuit breakers.一個(gè)小型的“開關(guān)站”可能在母線上加一些斷路器。 The largest transmission substations can cover a large area (several acres/hectares) with multiple voltage levels, and a large amount of protection and control equipment (capacitors, relays, switches, breakers, voltage and current transformers).最大的輸電站可覆蓋大面積（幾畝/公頃）的多電壓水平，大量的保護(hù)和控制設(shè)備（電容器，繼電器，開關(guān)，斷路器，電壓和電流互感器） 。 配電站 加拿大斯卡伯勒，安大略省的配電站就偽裝成了一所房子，配有車道，步道、前院的草坪和灌木。在“前門”上可以清楚的看到警告標(biāo)志。一個(gè)區(qū)域的配電站在傳輸系統(tǒng)和配電系統(tǒng)之間傳輸電力。用戶直接接入高壓住輸電網(wǎng)是非常不經(jīng)濟(jì)的，除非他們是用電大戶，因此，配電站降低電壓值以適合當(dāng)?shù)胤峙淝闆r。 一個(gè)配電站的輸入通常至少有兩條傳輸線。輸入電壓可為115 千伏 ，或該地區(qū)的額定值。輸出為一些饋線。配電電壓通常為中壓，電壓值在2.4和33 千伏之間，其取決于該地區(qū)的范圍。 饋線沿街道上空（或在城市的街道下）運(yùn)行 ，并最終為在客戶端或其附近的配電變壓器提供動(dòng)力 。 除了改變電壓，配電變電站的工作還隔離輸電系統(tǒng)或配電系統(tǒng)中的故障。配電變電站也可能是點(diǎn)的電壓調(diào)節(jié) ，但對(duì)長(zhǎng)期分配集成電路（幾公里/英里） ，電壓調(diào)節(jié)設(shè)備，也可安裝在沿線。 復(fù)雜的配電變電站一般在大型城市的市區(qū)，配有高壓開關(guān)，以及各種開關(guān)和低壓側(cè)的備用系統(tǒng)。更為典型的分布有一個(gè)變電站開關(guān)，一個(gè)變壓器，以及低壓側(cè)最小的設(shè)施。 集電式變電站在分布式發(fā)電工程中，如風(fēng)力發(fā)電場(chǎng) ，有可能需要集電式變電站。它有點(diǎn)類似于配電雖然潮流是相反的方向發(fā)展，許多風(fēng)力發(fā)電機(jī)成輸電。通常用于經(jīng)濟(jì)建設(shè)的集電式系統(tǒng)運(yùn)行約35千伏及集電式變電站臺(tái)階電壓輸電電壓的電網(wǎng)。集電極變電站還提供功率因數(shù)校正 ，測(cè)量和風(fēng)電場(chǎng)控制。 設(shè)計(jì) 電力工程師面臨的主要問題之一就是可靠性和成本。一個(gè)好的設(shè)計(jì)圖要求達(dá)到這兩者之間的平衡，以實(shí)現(xiàn)在較低的成本下得到滿意的可靠性。如果有需要，設(shè)計(jì)也應(yīng)該便于日后擴(kuò)建。 變電站的選址必須考慮許多因素。安裝所需設(shè)備與必要的電氣安全的充足面積，并獲得維持大型儀器如變壓器。如在城市地區(qū)，土地是昂貴的，選用氣體絕緣金屬封閉開關(guān)設(shè)備可省錢。由于負(fù)荷增長(zhǎng)或計(jì)劃傳輸補(bǔ)充，變電站必須有擴(kuò)展的余地。變電站還需考慮環(huán)境的影響，如排水 ，噪音和道路交通的影響。接地（接地）和對(duì)地電位升高必須計(jì)算在傳輸系統(tǒng)的保護(hù)之內(nèi)。當(dāng)然，變電站必須要根據(jù)地區(qū)重點(diǎn)進(jìn)行合理的分配。 布局 Tottenham Substation, set in wild parkland in North London托特納姆熱刺變電站，設(shè)置在倫敦北部野生公園，The first step in planning a substation layout is the preparation of a one-line diagram which shows in simplified form the switching and protection arrangement required, as well as the incoming supply lines and outgoing feeders or transmission lines.變電站布局規(guī)劃的第一步是編制一個(gè)線路圖顯示簡(jiǎn)化形式的開關(guān)和保護(hù)的安排需要，以及即將選用的輸電線和即將選用的饋線。作為It is a usual practice by many electrical utilities to prepare one-line diagrams with principal elements (lines, switches, circuit breakers, transformers) arranged on the page similarly to the way the apparatus would be laid out in the actual station.作為作慣例，許多電力公司準(zhǔn)備單行圖表主要內(nèi)容（線，開關(guān)，斷路器，變壓器）安排在網(wǎng)頁上的同樣的方式將機(jī)器中所規(guī)定的實(shí)際站。Incoming lines will almost always have a disconnect switch and a circuit breaker .傳入的生產(chǎn)線將幾乎總是有斷開開關(guān)和斷路器 。 In some cases, the lines will not have both; with either a switch or a circuit breaker being all that is considered necessary.在某些情況下，該行不會(huì)有兩個(gè)；帶有開關(guān)或斷路器被所有被認(rèn)為是必要的。 A disconnect switch is used to provide isolation, since it cannot interrupt load current.脫節(jié)的開關(guān)是用來提供隔離的，因?yàn)樗荒苤袛嘭?fù)載電流。 A circuit breaker is used as a protection device to interrupt fault currents automatically, and may be used to switch loads on and off.斷路器作為一種保護(hù)裝置故障電流自動(dòng)中斷，并可能被用來開關(guān)負(fù)荷。 When a large fault current flows through the circuit breaker, this may be detected through the use of current transformers.當(dāng)一個(gè)大故障電流流經(jīng)斷路器，這可能是由于使用電流互感器。電流互感器輸出The magnitude of the current transformer outputs may be used to trip the circuit breaker resulting in a disconnection of the load supplied by the circuit break from the feeding point.巨大的電流可使斷路器跳開并導(dǎo)致斷開負(fù)載。 This seeks to isolate the fault point from the rest of the system, and allow the rest of the system to continue operating with minimal impact.此舉旨在孤立故障點(diǎn)的其他制度，并允許其他的系統(tǒng)繼續(xù)運(yùn)作，將故障影響降到最低。 Both switches and circuit breakers may be operated locally (within the substation) or remotely from a supervisory control center.這兩個(gè)開關(guān)和斷路器可經(jīng)營(yíng)本地（在變電站）或遠(yuǎn)程監(jiān)控中心。 Once past the switching components, the lines of a given voltage connect to one or more buses .一旦過去的開關(guān)元件，按照特定的電壓連接到一條或多條母線。These are sets of bus bars , usually in multiples of three, since three-phase electrical power distribution is largely universal around the world.這是兩套母線 ，通常是在3的倍數(shù)，因?yàn)槭澜绺鞯仄毡槭褂萌嚯娏Α?The arrangement of switches, circuit breakers and buses used affects the cost and reliability of the substation.開關(guān)，斷路器和母線使用影響到變電站的成本和可靠性。 For important substations a ring bus , double bus , or so-called breaker and a half setup can be used, so that the failure of any one circuit breaker does not interrupt power to branch circuits for more than a brief time, and so that parts of the substation may be de-energized for maintenance and repairs.變電站重要的一種“一個(gè)半斷路器”接線方式，可以使任何一個(gè)跳閘的斷路器不會(huì)中斷供電，所以這部分變電站可帶電保養(yǎng)和維修。 Substations feeding only a single industrial load may have minimal switching provisions, especially for small installations.變電站喂養(yǎng)只有一個(gè)單一的工業(yè)負(fù)荷開關(guān)可能最小的規(guī)定，尤其是對(duì)小型設(shè)施。Once having established buses for the various voltage levels, transformers may be connected between the voltage levels.一旦建立了母線的各種電壓等級(jí)，變壓器可以連接之間的電壓水平。These will again have a circuit breaker, much like transmission lines, in case a transformer has a fault (commonly called a short circuit).這將再次有斷路器，就像輸電線路的情況下，變壓器的故障 （通常稱為短路）。Along with this, a substation always has control circuitry needed to command the various breakers to open in case of the failure of some component.與此同時(shí)，變電站始終控制電路所需的各種違法命令打開的情況下失敗的一些組成部分。 切換功能 變電站開關(guān)的An important function performed by a substation is switching , which is the connecting and disconnecting of transmission lines or other components to and from the system.一項(xiàng)重要的職能是連接和斷開輸電線路或其他部件和系統(tǒng)。A transmission line or other component may need to be deenergized for maintenance or for new construction; for example, adding or removing a transmission line or a transformer.傳輸線或其他部分可能需要進(jìn)行維修，或新添設(shè)備，例如，添加或刪除輸電線路或變壓器。 To maintain reliability of supply, no company ever brings down its whole system for maintenance.為了維持可靠的電力供應(yīng)，每一家公司都帶來了其整個(gè)系統(tǒng)進(jìn)行維修。All work to be performed, from routine testing to adding entirely new substations, must be done while keeping the whole system running.所有從事的工作，從日常測(cè)試，到增加新的變電站，只有這樣做，才能保持整個(gè)系統(tǒng)的運(yùn)行。 Perhaps more importantly, a fault may develop in a transmission line or any other component.也許更重要的是，故障可能發(fā)生在傳輸線或任何其他部分，例如：一條線被雷電擊中，并引起了電弧 ，或使高塔被風(fēng)刮倒。The function of the substation is to isolate the faulted portion of the system in the shortest possible time.變電站的功能是在盡可能短的時(shí)間內(nèi)支持孤立的部分系統(tǒng)。 There are two main reasons: a fault tends to cause equipment damage; and it tends to destabilize the whole system.主要有兩個(gè)原因：故障往往造成設(shè)備損壞；另外它往往破壞整個(gè)系統(tǒng)。For example, a transmission line left in a faulted condition will eventually burn down, and similarly, a transformer left in a faulted condition will eventually blow up.例如，處于故障狀態(tài)的輸電線路可能燒毀，類似的，發(fā)生故障的變壓器將可能最終炸毀。While these are happening, the power drain makes the system more unstable. Disconnecting the faulted component, quickly, tends to minimize both of these problems.故障元件需快速的斷開，以盡量減少這些問題。 鐵路Electrified railways also use substations which may also include rectifier equipment to change alternating current from the utility power distribution network to direct current for use by traction motors.電氣化鐵路變電站也使用變電站，而且可能還包括整流設(shè)備，以改變交流電從實(shí)用的配電網(wǎng)絡(luò)，以直流電使用牽引電機(jī)。A survey of substation communications technology An electrical substation is a subsidiary station of an electricity generation, transmission and distribution system where voltage is transformed from high to low or the reverse using transformers. Electric power may flow through several substations between generating plant and consumer, and may be changed in voltage in several steps.A substation that has a step-up transformer increases the voltage while decreasing the current, while a step-down transformer decreases the voltage while increasing the current for domestic and commercial distribution. The word substation comes from the days before the distribution system became a grid. The first substations were connected to only one power station where the generator was housed, and were subsidiaries of that power station.Elements of a substationSubstations generally contain one or more transformers, and have switching, protection and control equipment. In a large substation, circuit breakers are used to interrupt any short-circuits or overload currents that may occur on the network. Smaller distribution stations may use recloser circuit breakers or fuses for protection of branch circuits. Substations do not (usually) have generators, although a power plant may have a substation nearby. A typical substation will contain line termination structures, high-voltage switchgear, one or more power transformers, low voltage switchgear, surge protection, controls, grounding (earthing) system, and metering. Other devices such as power factor correction capacitors and voltage regulators may also be located at a substation.Substations may be on the surface in fenced enclosures, underground, or located in special-purpose buildings. High-rise buildings may have indoor substations. Indoor substations are usually found in urban areas to reduce the noise from the transformers, for reasons of appearance, or to protect switchgear from extreme climate or pollution conditions.Where a substation has a metallic fence, it must be properly grounded (UK: earthed) to protect people from high voltages that may occur during a fault in the transmission system. Earth faults at a substation can cause ground potential rise at the fault location. Currents flowing in the earths surface during a fault can cause metal objects to have a significantly different voltage than the ground under a persons feet; this touch potential presents a hazard of electrocution.Transmission substationA transmission substation connects two or more transmission lines. The simplest case is where all transmission lines have the same voltage. In such cases, the substation contains high-voltage switches that allow lines to be connected or isolated for maintenance. A transmission station may have transformers to convert between two transmission voltages, or equipment such as phase shifting transformers to control power flow between two adjacent power systems.Transmission substations can range from simple to complex. A small switching station may be little more than a bus plus some circuit breakers. The largest transmission substations can cover a large area (several acres/hectares) with multiple voltage levels, and a large amount of protection and control equipment (capacitors, relays, switches, breakers, voltage and current transformers).Distribution substationA distribution substation in Scarborough, Ontario, Canada disguised as a house, complete with a driveway, front walk and a mown lawn and shrubs in the front yard. A warning notice can be clearly seen on the front door.A distribution substation transfers power from the transmission system to the distribution system of an area. It is uneconomical to directly connect electricity consumers to the high-voltage main transmission network, unless they use large amounts of power, so the distribution station reduces voltage to a value suitable for local distribution.The input for a distribution substation is typically at least two transmission or subtransmission lines. Input voltage may be, for example, 115 kV, or whatever is common in the area. The output is a number of feeders. Distribution voltages are typically medium voltage, between 2.4 and 33 kV depending on the size of the area served and the practices of the local utility.The feeders will then run overhead, along streets (or under streets, in a city) and eventually power the distribution transformers at or near the customer premises.Besides changing the voltage, the job of the distribution substation is to isolate faults in either the transmission or distribution systems. Distribution substations may also be the points of voltage regulation, although on long distribution circuits (several km/miles), voltage regulation equipment may also be installed along the line.Complicated distribution substations can be found in the downtown areas of large cities, with high-voltage switching, and switching and backup systems on the low-voltage side. More typical distribution substations have a switch, one transformer, and minimal facilities on the low-voltage side.Collector substationIn distributed generation projects such as a wind farm, a collector substation may be required. It somewhat resembles a distribution substation although power flow is in the opposite direction, from many wind turbines up into the transmission grid. Usually for economy of construction the collector system operates around 35 kV, and the collector substation steps up voltage to a transmission voltage for the grid. The collector substation also provides power factor correction, metering and control of the wind farm.DesignThe main issues facing a power engineer are reliability and cost. A good design attempts to strike a balance between these two, to achieve sufficient reliability without excessive cost. The design should also allow easy expansion of the station, if required.Selection of the location of a substation must consider many factors. Sufficient land area is required for installation of equipment with necessary clearances for electrical safety, and for access to maintain large apparatus such as transformers. Where land is costly, such as in urban areas, gas insulated switchgear may save money overall. The site must have room for expansion due to load growth or planned transmission additions. Environmental effects of the substation must be considered, such as drainage, noise and road traffic effects. Grounding (earthing) and ground potential rise must be calculated to protect passers-by during a short-circuit in the transmission system. And of course, the substation site must be reasonably central to the distribution area to be served.LayoutTottenham Substation, set in wild parkland in North LondonThe first step in planning a substation layout is the preparation of a one-line diagram which shows in simplified form the switching and protection arrangement required, as well as the incoming supply lines and outgoing feeders or transmission lines. It is a usual practice by many electrical utilities to prepare one-line diagrams with principal elements (lines, switches, circuit breakers, transformers) arranged on the page similarly to the way the apparatus would be laid out in the actual station.Incoming lines will almost always have a disconnect switch and a circuit breaker. In some cases, the lines will not have both; with either a switch or a circuit breaker being all that is considered necessary. A disconnect switch is used to provide isolation, since it cannot interrupt load current. A circuit breaker is used as a protection device to interrupt fault currents automatically, and may be used to switch loads on and off. When a large fault current flows through the circuit breaker, this may be detected through the use of current transformers. The magnitude of the current transformer outputs may be used to trip the circuit breaker resulting in a disconnection of the load supplied by the circuit break from the feeding point. This seeks to isolate the fault point from the rest of the system, and allow the rest of the system to continue operating with minimal impact. Both switches and circuit breakers may be operated locally (within the substation) or remotely from a supervisory control center.Once past the switching components, the lines of a given voltage connect to one or more buses. These are sets of bus bars, usually in multiples of three, since three-phase electrical power distribution is largely universal around the world.The arrangement of switches, circuit breakers and buses used affects the cost and reliability of the substation. For important substations a ring bus, double bus, or so-called breaker and a half setup can be used, so that the failure of any one circuit breaker does not interrupt power to branch circuits for more than a brief time, and so that parts of the substation may be de-energized for maintenance and repairs. Substations feeding only a single industrial load may have minimal switching provisions, especially for small installations.Once having established buses for the various voltage levels, transformers may be connected between the voltage levels. These will again have a circuit breaker, much like transmission lines, in case a transformer has a fault (commonly called a short circuit).Along with this, a substation always has control circuitry needed to command the various breakers to open in case of the failure of some component.Switching functionAn important function performed by a substation is switching, which is the connecting and disconnecting of transmission lines or other components to and from the system. Switching events may be planned or unplanned.A transmission line or other component may need to be reenergized for maintenance or for new construction; for example, adding or removing a transmission line or a transformer.To maintain reliability of supply, no company ever brings down its whole system for maintenance. All work to be performed, from routine testing to adding entirely new substations, must be done while keeping the whole system running.Perhaps more importantly, a fault may develop in a transmission line or