國電霍州發(fā)電廠2×600MW超臨界空冷凝汽式火電廠畢業(yè)設(shè)計(jì)說明書

1、國電霍州發(fā)電廠2×600MW超臨界空冷凝汽式火電廠畢業(yè)設(shè)計(jì)說明書 內(nèi)蒙古科技大學(xué) 本科生畢業(yè)設(shè)計(jì)說明書（畢業(yè)論文） 題 目：2×600MW火力發(fā)電廠 廠用電設(shè)計(jì) 學(xué)生姓名：葉斌 學(xué) 號(hào)：0705130113 專 業(yè)：電氣工程及其自動(dòng)化 班 級(jí)：電氣07-1班 指導(dǎo)教師：李潔(教授) 內(nèi)蒙古科技大學(xué)畢業(yè)設(shè)計(jì)說明書（畢業(yè)論文） 摘要 火力發(fā)電廠是電力系統(tǒng)的重要組成部分，也直接影響整個(gè)電力系統(tǒng)的安全與運(yùn)行。發(fā)電廠廠用電系統(tǒng)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。因此，發(fā)電廠廠用電系統(tǒng)的設(shè)計(jì)是否合理，對(duì)保證廠用負(fù)荷的連續(xù)供電乃至發(fā)電廠和電力系統(tǒng)的安全經(jīng)濟(jì)運(yùn)行至關(guān)重要。 本設(shè)計(jì)結(jié)合

2、國電霍州發(fā)電廠“上大壓小”2×600MW超臨界空冷機(jī)組工程的實(shí)際情況，主要闡述火電廠廠用電設(shè)計(jì)原理。主接線采用了3/2斷路器交叉接線的形式。廠用電部分依據(jù)按爐分段原則，每臺(tái)機(jī)組設(shè)置A、B兩段母線供電，不設(shè)置公用段（公用負(fù)荷分?jǐn)偟綇S用工作母線上）。突出介紹了直接空冷系統(tǒng)的電氣設(shè)計(jì)、濕法脫硫系統(tǒng)、廠用負(fù)荷的計(jì)算、廠用變壓器的選擇以及廠用電動(dòng)機(jī)自啟動(dòng)。為了計(jì)算方便，短路計(jì)算運(yùn)用運(yùn)算曲線法并采用標(biāo)幺值進(jìn)行。 通過對(duì)電氣主接線的設(shè)計(jì)、廠用電的設(shè)計(jì)和計(jì)算、短路電流的計(jì)算、電氣設(shè)備的選擇和校驗(yàn)以及配電裝置的設(shè)計(jì)，簡要完成了2×600MW超臨界空冷機(jī)組的電氣一次部分的設(shè)計(jì)。 關(guān)鍵詞：火力發(fā)

3、電廠；電氣一次部分；短路電流；電氣設(shè)備。 1 內(nèi)蒙古科技大學(xué)畢業(yè)設(shè)計(jì)說明書（畢業(yè)論文） ABSTRACT Thermal power plant is an important part of the power system, and also affect the whole power system security and operation.The design of power plant auxiliary power system is an essential project in the electric power industry construction. There

4、fore,whether the design of power plant auxiliary power pystem is reasonable, is very important to ensure that load of plant supply electric power continuously, even the safe and economic operation of the Power Plant and the Power System. This paper mainly expounds the design principle of the power p

5、lant auxiliary power pystem, witch combine with the actual situation of project of GuoDian HuoZhou 2×600MW supercritical air-cooling units witch replaces small units. The main electric wiring witch is cross wiring adopted 3/2 circuit breaker form. According to the principle of boiler section th

6、e part of auxiliary power system, each unit set A, B the two parts of the bus supply power,has not set public bus(public load allocation to the main busbar) It introduces the direct air-cooling system and wet desulphurization system electrical design, calculate to load of plant, selection for statio

7、n transformator, self-starting of plant motor prominently. Operation Curve Method and Per Unit have been used for the short-circuit current calculation in order to make it convenient. Through design and computation of the main electrical wiring and the auxiliary power system, short-circuit current c

8、omputation, electrical equipment choice and verification as well as power distribution equipment, this article briefly completed 2×600MW supercritical air-cooling units electrical partial designs KEY WORDS: Thermal power plant; The electrical part; The short-circuit current；Electrical equipment

9、. 2 內(nèi)蒙古科技大學(xué)畢業(yè)設(shè)計(jì)說明書（畢業(yè)論文） 摘要 ·············································&#

10、183;·················································&#

11、183;······························· 1 ABSTRACT ················&#

12、183;·················································&#

13、183;················································ 2 第1章 工

14、程簡介及原始資料分析 ················································&

15、#183;·························· 6 第2章 2×600MW機(jī)組電氣主接線設(shè)計(jì) ··················&#

16、183;············································· 7 2.1 電氣主接線概述 ··

17、;··················································

18、;··········································· 7 2.2 600MW機(jī)組電氣主接線基本接線形式··

19、3;·················································

20、3;···· 7 2.3 電氣主接線形式的確定 ··········································

21、3;······································ 10 2.4 主變壓器的選擇 ·········

22、··················································

23、·································· 11 2.4.1 主變壓器形式選擇 ·············

24、;··················································

25、;··················· 11 2.4.2 主變壓器容量選擇 ···························

26、3;·················································

27、3;···· 12 第3章 2×600MW機(jī)組廠用電設(shè)計(jì) ·········································

28、····························· 13 3.1 廠用電概述及設(shè)計(jì)原則 ··················

29、;··················································

30、;············· 13 3.2 廠用電的電壓等級(jí)確定 ·································

31、3;··············································· 14 3.3 廠用電源及其引接

32、方式 ·················································

33、83;······························· 15 3.3.1 廠用工作電源及其引接 ···············

34、··················································

35、········· 15 3.3.2 啟動(dòng)/備用電源及其引接 ·····································&#

36、183;··································· 15 3.3.3 事故保安電源及其引接 ···········

37、;··················································

38、;············· 16 3.4 廠用電接線設(shè)計(jì) ··································&

39、#183;·················································&

40、#183;········ 16 3.4.1 10kV高壓廠用母線接線設(shè)計(jì) ·····································

41、··························· 16 3.4.2 直接空冷系統(tǒng)電氣設(shè)計(jì) ···················

42、83;·················································

43、83;···· 17 3.4.3 濕法脫硫系統(tǒng)電氣設(shè)計(jì) ··········································

44、································ 17 3.4.4 380/220V低壓廠用電系統(tǒng)接線設(shè)計(jì) ·············

45、········································ 18 3.5 廠用負(fù)荷計(jì)算 ·······

46、83;·················································

47、83;········································· 19 3.5.1 廠用電負(fù)荷及其分類 ·····&

48、#183;·················································&

49、#183;······················ 19 3.5.2 廠用電負(fù)荷的計(jì)算原則 ·······················

50、3;·················································

51、3; 21 3.5.3 廠用負(fù)荷的計(jì)算方法 ··············································&#

52、183;······························· 22 3.5.4 電動(dòng)機(jī)計(jì)算功率確定 ···············

53、··················································

54、············· 22 3.5.5 10kV集中濕法脫硫段負(fù)荷計(jì)算 ································

55、3;··························· 23 3.5.6 10kV高壓廠用工作母線負(fù)荷統(tǒng)計(jì)算 ··················

56、·································· 24 3.6 廠用變壓器的選擇 ·············&

57、#183;·················································&

58、#183;························· 25 3 內(nèi)蒙古科技大學(xué)畢業(yè)設(shè)計(jì)說明書（畢業(yè)論文） 3.6.1 變壓器選擇的基本原則和應(yīng)考慮的因素 ···············

59、3;······························ 25 3.6.2 高壓廠用變壓器的容量及形式選擇 ···············&#

60、183;······································ 25 3.6.3 啟動(dòng)/備用變壓器的容量及形式選擇 ·······

61、;·············································· 26 3.6.4 低壓廠用變壓器的容量及形式

62、選擇 ·················································

63、83;···· 26 3.6.5 廠用電率的計(jì)算 ··········································

64、83;··········································· 29 3.7 廠用電動(dòng)機(jī)自啟動(dòng) ···

65、3;·················································

66、3;··································· 30 3.7.1 電動(dòng)機(jī)自啟動(dòng)校驗(yàn)條件 ···········&

67、#183;·················································&

68、#183;············ 30 3.7.2 電動(dòng)機(jī)自啟動(dòng)分類 ··································

69、················································ 31 3.7.3 電動(dòng)

70、機(jī)自啟動(dòng)時(shí)廠用母線電壓最低限值 ·············································· 31 3.7.

71、4 電動(dòng)機(jī)自啟動(dòng)校驗(yàn)內(nèi)容 ················································

72、;·························· 32 3.7.5 電動(dòng)機(jī)自啟動(dòng)校驗(yàn)方法 ····················&#

73、183;·················································&#

74、183;··· 32 3.7.6 高壓廠用電動(dòng)機(jī)單獨(dú)自啟動(dòng)電壓校驗(yàn) ··········································

75、;········ 35 3.7.7 高、低壓廠用電動(dòng)機(jī)串聯(lián)自啟動(dòng)電壓校驗(yàn) ·····································

76、····· 36 第4章 短路計(jì)算 ···········································

77、;··················································

78、;········ 39 4.1 短路計(jì)算的目的、條件及方法 ······································&

79、#183;······························ 39 4.2 系統(tǒng)各元件電抗標(biāo)幺值的計(jì)算 ···············

80、83;·················································

81、83;··· 40 4.3 短路計(jì)算 ············································&#

82、183;·················································&#

83、183;·········· 41 第5章 電氣設(shè)備選擇 ·····································

84、;··················································

85、;······ 48 5.1 電氣設(shè)備選擇的要求和原則 ········································&#

86、183;································ 48 5.2 廠用母線的選擇 ··············

87、3;·················································

88、3;···························· 50 5.2.1 10kV 高壓廠用母線選擇 ·················

89、3;·················································

90、3;··· 51 5.2.2 0.38kV低壓廠用母線選擇 ··········································

91、83;·························· 53 5.2.3 封閉母線的選擇 ····················

92、83;·················································

93、83;··············· 56 5.3 斷路器及隔離開關(guān)的選擇 ·······························&

94、#183;············································· 56 5.4 互感器的選擇 ·

95、3;·················································

96、3;············································· 57 5.4.1 電流互感器的選擇 ·

97、83;·················································

98、83;······························ 57 5.4.2 電壓互感器的選擇 ················&#

99、183;·················································&#

100、183;··············· 59 5.5 高、低壓開關(guān)柜的選擇 ·······························&

101、#183;·················································

102、61 5.5.1 10kV高壓開關(guān)柜的選擇 ··············································&#

103、183;························· 61 5.5.2 低壓開關(guān)柜的選擇 ·····················&

104、#183;·················································&

105、#183;·········· 62 4 內(nèi)蒙古科技大學(xué)畢業(yè)設(shè)計(jì)說明書（畢業(yè)論文） 5.6 設(shè)備清單表 ·································

106、··················································

107、·················· 63 總結(jié) ·······························

108、;··················································

109、;············································ 64 參考文獻(xiàn) ····&#

110、183;·················································&#

111、183;·················································&#

112、183;············ 65 附錄 ····································&

113、#183;·················································&

114、#183;······································ 66 致謝 ··········

115、··················································

116、··················································

117、··············· 67 5 內(nèi)蒙古科技大學(xué)畢業(yè)設(shè)計(jì)說明書（畢業(yè)論文） 第1章 工程簡介及原始資料分析 一、工程簡介 國電霍州發(fā)電廠2×600MW以大代小工程是拆除老廠4×100MW機(jī)組，在原場地上建設(shè)。本期工程建設(shè)規(guī)模為2×600MW空冷凝汽式汽輪發(fā)電機(jī)組配超臨界燃煤鍋爐，以一回500kV線路接入霍州500kV變電站，起動(dòng)/備用電源由廠外霍州寺莊220kV變電站引接。本期新建的主要工藝設(shè)施有：2臺(tái)600

118、MW容量空冷凝汽式汽輪發(fā)電機(jī)組、鍋爐及其輔助系統(tǒng)、脫硫系統(tǒng)、電除塵器及除灰系統(tǒng)、運(yùn)煤系統(tǒng)、供水系統(tǒng)、采暖通風(fēng)系統(tǒng)和水處理系統(tǒng)等。 二、原始資料分析 1、類型：2×600MW超臨界直接空冷凝汽式火電廠； 2、年負(fù)荷最大利用小時(shí)數(shù)：Tmax=6300h； 3、發(fā)電機(jī)采用東方QFSN-600-2型發(fā)電機(jī)，其主要技術(shù)數(shù)據(jù)如下表： 表1-1 東方QFSN-600-2-22型發(fā)電機(jī)參數(shù) 4、電力負(fù)荷水平：500kV電壓等級(jí)以一回出線送至距離發(fā)電廠35km的霍州500kV變電所； 5、平均海拔標(biāo)高：1000m； 6、年平均氣溫：12.1，氣象條件無其它特殊要求； 三、設(shè)計(jì)過程中可能用到的數(shù)據(jù)假設(shè)

119、1、主保護(hù)動(dòng)作時(shí)間：tprl=0.05s； 2、短路電流非周期分量衰減時(shí)間常數(shù)：Ta=0.25s； 3、各類母線統(tǒng)一?。合嚅g距離a=0.35m，相鄰絕緣子的跨距L=1.5，動(dòng)態(tài)應(yīng)力系數(shù)=1； 4、短路切除時(shí)間（短路電流熱效應(yīng)計(jì)算時(shí)間）：tk=1.2s。 6 內(nèi)蒙古科技大學(xué)畢業(yè)設(shè)計(jì)說明書（畢業(yè)論文） 第2章 2×600MW機(jī)組電氣主接線設(shè)計(jì) 2.1 電氣主接線概述 將高壓電氣設(shè)備（包括發(fā)電機(jī)、變壓器、母線、斷路器、隔離開關(guān)、線路等）的圖形用單線繪制成的接線圖，稱為電氣主接線。電氣主接線方式的選擇，是為滿足功率傳輸要求，對(duì)安全性、經(jīng)濟(jì)性、可靠性、靈活性的輸送電能起著決定性作用。 對(duì)一個(gè)裝

120、有600MW機(jī)組的電廠而言，電氣主接線在電廠設(shè)計(jì)時(shí)就已經(jīng)根據(jù)機(jī)組容量、電廠規(guī)模及電廠在電力系統(tǒng)中的地位、供電負(fù)荷的距離等，以及保證輸、供電可靠性、運(yùn)行靈活性、經(jīng)濟(jì)性、發(fā)展和擴(kuò)建的可能性等方面，并經(jīng)綜合比較后確定。 2.2 600MW機(jī)組電氣主接線基本接線形式 本節(jié)主要介紹裝有大容量（600MW及以上）汽輪發(fā)電機(jī)組的發(fā)電廠有關(guān)的基本主接線形式。 一、雙母線接線 1一般雙母線接線 如圖2-1所示，它具有兩組母線：工作母線和備用母線。每回進(jìn)出線均經(jīng)一組斷路器和兩組母線隔離開關(guān)分別接至兩組母線，兩組母線間通過母線聯(lián)絡(luò)斷路器QFc相連。有兩組母線后， 使運(yùn)行的可靠性和靈活性大為提 高，其特點(diǎn)如下： （1

121、）檢修任意一組母線時(shí)， 不會(huì)停止對(duì)用戶的連續(xù)供電。例如， 檢修母線時(shí)，可把全部電源和復(fù) 合線路切換到母線上。 （2）運(yùn)行調(diào)度靈活，通過倒 換操作可以實(shí)現(xiàn)不同形式的運(yùn)行 方式。當(dāng)母聯(lián)斷路器QFc閉合，進(jìn)出線適當(dāng)?shù)胤峙湓趦山M母線上，形成雙母線同時(shí)運(yùn)行的狀態(tài)（相當(dāng)于單母線分段的運(yùn)行方式） 。有時(shí)為了系統(tǒng)的需要，亦可 7 內(nèi)蒙古科技大學(xué)畢業(yè)設(shè)計(jì)說明書（畢業(yè)論文） 將母聯(lián)斷路器斷開（處于熱備用狀態(tài)），兩組母線同時(shí)運(yùn)行。這時(shí)該電廠相當(dāng)于分裂成兩個(gè)電廠各自向系統(tǒng)送電。顯然，兩組母線同時(shí)運(yùn)行的供電可靠性比只有一組母線運(yùn)行時(shí)高。 2雙母線帶旁路母線接線 一般雙母線接線的主要缺點(diǎn)是，檢修線路斷路器會(huì)造成該回路停電

122、。為了檢修線路斷路器時(shí)不致造成停電，可采用帶旁路母線的雙母線（應(yīng)該注意的是旁路母線只為檢修斷路器時(shí)不中斷 供電而設(shè)，它不能代替匯流母 線），如圖2-2所示。在每一回 路的線路側(cè)裝設(shè)一組隔離開關(guān) （旁路隔離開關(guān)）QS，接到旁 路母線上，而旁路母線再經(jīng) 旁路斷路器和旁路隔離開關(guān)接 到兩組母線上。圖2-2中設(shè)有專 用的旁路斷路器QF，要檢修某 一線路的斷路器時(shí)，基本操作步驟：先合旁路斷路器兩側(cè)的隔離開關(guān)（母線側(cè)合上一個(gè)），再合上旁路斷路器QF對(duì)旁路母線進(jìn)行充電與檢查；若旁路母線正常，則待檢修的斷路器回路上的旁路隔離開關(guān)兩側(cè)已經(jīng)等電位，可以合上該旁路隔離開關(guān)；此后可斷開帶檢修短路器及其兩側(cè)的隔離開關(guān)，

123、對(duì)斷路器進(jìn)行檢修。此時(shí)已通過旁路斷路器、旁路母線及有關(guān)旁路隔離開關(guān)想起供電。 3雙母線分段接線 雙母線接線難以滿足大型電廠和變電所對(duì)主接線可靠性的要求：不分段的雙母線接線在母聯(lián)斷路器故 障或一組母線檢修，另一 組運(yùn)行母線故障時(shí)，有可 能造成嚴(yán)重的或全廠（所） 停電事故。 如圖2-3為雙母線分 段接線。用分段斷路器 QF3 8 QF1 QF2 內(nèi)蒙古科技大學(xué)畢業(yè)設(shè)計(jì)說明書（畢業(yè)論文） 把工作母線分段，每段分別用母聯(lián)斷路器QF1和QF2與備用母線相連。這種接線比一般的雙母線接線具有更高的供電可靠性與靈活性。但由于斷路器較多，投資較大，一般在進(jìn)出線路較多（如多于8回線路）時(shí)可能用這種接線。 以上三種

124、雙母線接線方式具有供電可靠、檢修方便、調(diào)度靈活及便于擴(kuò)建等優(yōu)點(diǎn)，在國內(nèi)大中型電廠和變電所廣泛采用。但是這種接線所用設(shè)備多，在運(yùn)行中隔離開關(guān)作為操作電器，交易發(fā)生誤操作。特別是當(dāng)母線系統(tǒng)發(fā)生故障時(shí)，需要短時(shí)間內(nèi)切除較多電源和線路，這對(duì)于特別重要的大型發(fā)電廠變電所是不容許的。 二、3/2斷路器接線 如圖2-4所示，在上和下兩組母線之間有3個(gè)斷路器構(gòu)成一串，給2個(gè)元件（出線或電源）使用，每個(gè)元件占用3/2斷路器。稱為3/2斷路器接線，又稱3/2接線。 正常運(yùn)行時(shí)，兩組母線和同一串的三個(gè)斷路器都 投入運(yùn)行，稱為完整串運(yùn)行，形形成多環(huán)路狀供電， 具有很高的可靠性。 其主要特點(diǎn)是，任一組母線故障或檢修時(shí)，

125、只斷 開與此母線相連的所有斷路器，所有回路都不會(huì)停電。 任一斷路器檢修時(shí)，所有回路都不會(huì)停電(每個(gè)回路都 經(jīng)過兩臺(tái)斷路器供電)。甚至在一組母線檢修另一組母 線故障或兩組母線同時(shí)故障的極端情況下，也不中斷 供電。一串中任何一臺(tái)斷路器退出或檢修時(shí)，這種運(yùn) 行方式稱為不完全串運(yùn)行，此此時(shí)任然不影響任何元 件的運(yùn)行。這種接線運(yùn)行方便、操作簡單，隔離開關(guān) 只在檢修時(shí)作為隔離電器用。 在裝設(shè)600MW機(jī)組的大容量電廠中，廣泛采用3/2斷路器接線。在電廠一期工程中，一般機(jī)組和出現(xiàn)數(shù)較少。如本期2×600MW工程，只有兩臺(tái)發(fā)電機(jī)和兩回出線（一回送至霍州500kV變電所，一回備用），構(gòu)成只有兩串的3/

126、2斷路器接線。在此情況下，電源（進(jìn)線）和出線的接入點(diǎn)可采用兩種方式：一種是交叉接線，如圖2-5（a）所示，將兩個(gè)同名元件（電源或出線）分別布置在不同 9 內(nèi)蒙古科技大學(xué)畢業(yè)設(shè)計(jì)說明書（畢業(yè)論文） 串上，并且分別靠近不同母線接入，即電源（變壓器）和出線相互交叉配置；另一種是非交叉接線，如圖2-5（b）所示，它也將同名元件（電源或出線）分別布置在不同串上，但所有同名元件都靠近同一母線一側(cè)（進(jìn)線都靠近一組母線，出線都靠近一組母線）。 通過分析可知：3/2交叉接線比3/2非交叉接線具有更高的運(yùn)行可靠性，可以減少特殊運(yùn)行方式下事故擴(kuò)大。例如，一串中的聯(lián)絡(luò)斷路器（設(shè)502）在檢修或停用，當(dāng)另一串的聯(lián)絡(luò)斷路

127、器發(fā)生異常跳閘或事故跳閘（出線L2故障或進(jìn)線T2回路故障）時(shí)，對(duì)非交叉接線將造成切除兩個(gè) 電源，相應(yīng)的兩臺(tái)發(fā)電機(jī)甩負(fù)荷至零，電廠與系統(tǒng)完全解列；而對(duì)交叉接線而言，至少還有一個(gè)電源（發(fā)電機(jī)變壓器）可向系統(tǒng)送電，L2故障時(shí)T2向L1送電，T2故障時(shí)T1向L2送電，僅是聯(lián)絡(luò)斷路器505異常跳開時(shí)也不破壞兩臺(tái)發(fā)電機(jī)向系統(tǒng)送電。 應(yīng)當(dāng)指出，當(dāng)3/2接線的串?dāng)?shù)多于兩串時(shí)，由于線路本身構(gòu)成的閉環(huán)回路不止一個(gè)，一個(gè)串中的聯(lián)絡(luò)斷路器檢修或停用時(shí)，任然還有閉環(huán)回路，因此不存在交叉接線的優(yōu)點(diǎn)。 L1 L2 L1L2 2.3 電氣主接線形式的確定 本期工程2×600MW超臨界空冷凝汽機(jī)組以500kV一級(jí)電壓

128、接入系統(tǒng)，電廠出線1回，接入霍州500kV變電站。500kV系統(tǒng)采用3/2交叉接線。 考慮到電廠長期運(yùn)行，本期工程電氣采用聯(lián)合單元接線，主變側(cè)設(shè)有斷路器，可避免一臺(tái)機(jī)組檢修和投運(yùn)時(shí)影響另一臺(tái)機(jī)組的正常運(yùn)行；起/備變電源可利用現(xiàn)有的220kV霍寺線引接。 結(jié)合系統(tǒng)總體規(guī)劃及本工程近期規(guī)劃情況，從確保系統(tǒng)可靠性、減少運(yùn)行維護(hù)工作量、降低工程造價(jià)等方面考慮，本工程發(fā)電機(jī)與主變之間的連接采用全連式分相封閉母線。發(fā)電機(jī)與主變壓器之間不裝設(shè)斷路器，只設(shè)可拆連接片，以供 10 內(nèi)蒙古科技大學(xué)畢業(yè)設(shè)計(jì)說明書（畢業(yè)論文） 檢修和調(diào)試使用。（發(fā)電機(jī)出口不裝設(shè)斷路器，其理由是，大電流大容量斷路器投資較大，而且發(fā)電機(jī)

129、出口到主變壓器和廠用工作母線采用全連式分相封閉母線后，此段線路范圍內(nèi)，相間短路故障的可能性亦已降低。）此方案接線簡單、投資低、布置簡單。 高壓廠用變壓器和勵(lì)磁變壓器由發(fā)電機(jī)與主變低壓側(cè)之間引接。 2.4 主變壓器的選擇 2.4.1 主變壓器形式選擇 在發(fā)電廠中，用來向電力系統(tǒng)或用戶輸送功率的變壓器，稱為主變壓器。 （1）相數(shù)的確定 主變壓器采用三相或單相，主要考慮變壓器的制造條件，可靠性要求及運(yùn)輸條件等因素。容量為300MW級(jí)以下機(jī)組單元連接的主變壓器和300kV級(jí)以下電力系統(tǒng)中，一般都應(yīng)采用三相變壓器。500kV及以上電力系統(tǒng)，應(yīng)根據(jù)制造、運(yùn)輸條件和可靠性要求等因素，經(jīng)技術(shù)經(jīng)濟(jì)比較后，確定采

130、用三相還是單相變壓器。若選用單相變壓器組，可以考慮系統(tǒng)和設(shè)備的情況，裝設(shè)一臺(tái)備用相變壓器。本設(shè)計(jì)采用三相變壓器。 （2）繞組數(shù)的確定 電力變壓器的每相繞組數(shù)分為雙繞組、三繞組或更多繞組等形式；按電磁結(jié)構(gòu)分為普通雙繞組、三繞組、自耦式及低壓繞組分裂式等型式。機(jī)組容量為200MW以上的發(fā)電廠，其升壓變壓器一般不采用三繞組變壓器。因?yàn)樵诎l(fā)電機(jī)回路及廠用分支回路均采用分相封閉母線，供電可靠性很高，而大電流的隔離開關(guān)發(fā)熱問題比較突出等等。本設(shè)計(jì)采用雙繞組變壓器。 （3）有載調(diào)壓變壓器的使用條件 在電壓變化范圍大且變化頻繁的情況下需使用有載調(diào)壓變壓器。 有載調(diào)壓變壓器的價(jià)格較貴，質(zhì)量不行大大降低其可靠性，

131、所以應(yīng)慎用。一般中小電廠設(shè)立發(fā)電機(jī)電壓母線的，連接該母線與高、中壓電網(wǎng)的變壓器可能出現(xiàn)功率倒送，為保證母線負(fù)荷供電電壓質(zhì)量要求，通常要帶負(fù)荷調(diào)節(jié)電壓；地方變電站、工礦企業(yè)的自用變電站往往日負(fù)荷變化幅度很大，要滿足電能質(zhì)量也需帶負(fù)載調(diào)壓；330kV及以上的變電站在晝夜負(fù)荷變化時(shí)高壓側(cè)端電壓變化很大，為維持中低壓電壓水平需裝設(shè)有載調(diào)壓變壓器 11 內(nèi)蒙古科技大學(xué)畢業(yè)設(shè)計(jì)說明書（畢業(yè)論文） 2.4.2 主變壓器容量選擇 由于本工程采用發(fā)電機(jī)變壓器單元接線，主變壓器容量一般按變電所建成后510年的規(guī)劃負(fù)荷來進(jìn)行選擇，并適當(dāng)考慮遠(yuǎn)期1020年的負(fù)荷發(fā)展。根據(jù)DL50002000火力發(fā)電廠設(shè)計(jì)技術(shù)規(guī)定：“主變壓器的容量可按發(fā)電機(jī)的最大連續(xù)容量扣除一臺(tái)廠用變壓器的計(jì)算負(fù)荷后留有10%的裕度選擇” SN=1.1PN 1?KP /cosG (MVA) (2?1) 式中 PN發(fā)電機(jī)的額定功率 （MW）； cosG發(fā)電機(jī)額定功率因數(shù)； KP廠用電率。 由前面廠用電率計(jì)算值6.0代入公式(2-1)得： SN=1.1PN 1?KP cosG=1.1&#